The Impact of Different Intraoperative Fluid Administration Strategies on Postoperative Extubation Following Multilevel Thoracic and Lumbar Spine Surgery: A Propensity Score Matched Analysis

The Impact of Different Intraoperative Fluid Administration Strategies on Postoperative... Abstract BACKGROUND Patients undergoing multilevel spine surgery are at risk for delayed extubation. OBJECTIVE To evaluate the impact of type and volume of intraoperative fluids administered during multilevel thoracic and/or lumbar spine surgery on postoperative extubation status. METHODS Retrospective evaluation of medical records of patients ≥ 18 yr undergoing ≥ 4 levels of thoracic and/or lumbar spine fusions was performed. Patients were organized according to postoperative extubation status: immediate (IMEX; in OR/PACU) or delayed (DEX; outside OR/PACU). Propensity score matched (PSM) analysis was performed to compare IMEX and DEX groups. Volume, proportion, and ratios of intraoperative fluids administered were evaluated for the associated impact on extubation status. RESULTS A total of 246 patients (198 IMEX, 48 DEX) were included. PSM analysis demonstrated that increased administration of non-cell saver blood products (NCSB) and increased ratio of crystalloid: colloids infused were independently associated with delayed extubation. With increasing EBL, IMEX had a proportionate reduction in crystalloid infusion (R = –0.5, P < .001), while the proportion of crystalloids infused remained relatively unchanged for DEX (R = –0.27; P = .06). Twenty-six percent of patients receiving crystalloid: colloid ratio > 3:1 had DEX compared to none of those receiving crystalloid: colloid ratio ≤ 3:1 (P = .009). DEX had greater cardiac and pulmonary complications, surgical site infections and prolonged intensive care unit and hospital stay (P < .05). CONCLUSION PSM analysis of patients undergoing multilevel thoracic and/or lumbar spine fusion demonstrated that increased administration of crystalloid to colloid ratio is independently associated with delayed extubation. With increasing EBL, a proportionate reduction of crystalloids facilitates early extubation. Delayed extubation, Fluid resuscitation, Early complications, Multilevel, Spinal Fusion, Surgical invasiveness ABBREVIATIONS ABBREVIATIONS ASA American Society of Anesthesiologists BMI body mass index CCI Charlson co-morbidity index DEX delayed extubation EBL estimated blood loss EBV Estimated blood volume EBVL estimated intraoperative blood volume loss IMEX immediate extubation group ICU intensive care unit NCSB non-cell saver blood OR operating room PRBC packed red blood cells PACU post-anesthesia care unit PSM Propensity score matched SII surgical invasiveness index Improved understanding of spine anatomy and advances in fusion techniques have enabled surgeons to more commonly perform complex spine procedures, as demonstrated by increasing rates of multilevel spine fusion procedures over the past decade.1 However, multilevel spine fusion procedures are associated with high complication rates.2-4 These procedures often involve large incisions with extensive soft tissue dissection and periosteal exposure over large areas of the spine, which triggers a massive systemic inflammatory response.5 The combination of soft tissue trauma, systemic inflammation, and prolonged intraoperative anesthesia can alter the patient's vascular integrity, thereby impacting fluid requirements, fluid responsiveness, and generate large intra and extravascular fluid shifts.6 These fluid shifts in association with prone surgical positioning can cause delayed postoperative extubation. Prolonged endotracheal intubation is associated with a multitude of complications including airway and pulmonary edema, pneumonia, stasis ulcers, wound dehiscence, and prolonged intensive care unit (ICU) and hospital length of stay.7-10 Optimal intraoperative fluid replacement protocols for surgeries that involve large blood loss and prolonged surgical times remain controversial.11-13 According to a recent meta-analysis, there is currently insufficient evidence to suggest advantages of administering one type of fluids over another during elective noncardiac procedures.14 Synthetic colloids are often administered since they can maintain intravascular fluid volume and regional tissue perfusion more efficiently than crystalloids. However, there has been reported a potential increased risk of renal failure and coagulation disorders with the use of intraoperative colloid solutions.15 With respect to spine surgery, few studies have examined the role of intraoperative fluid administration on postoperative extubation status.16-19 Anastasian et al16 reported that age, American Society of Anesthesiologists (ASA) Grade, procedure duration, magnitude of surgery, total crystalloid and blood volumes administered, and procedure end-time correlated with delayed extubation after multilevel spine surgery. Similarly, Nahtomi-Shick et al17 reported that increased intraoperative administration of blood products and crystalloids was associated with increased ICU length of stay for patients undergoing spinal surgeries; however, the authors did not evaluate postoperative extubation status or reasons for prolonged care. Consequently, the impact that the type and proportion of intraoperative fluids administered during multilevel spine surgery has upon postoperative extubation remains uncertain. The objective of this study was to perform a propensity score matched (PSM) analysis of patients undergoing multilevel thoracic and/or lumbar spine fusion procedures to determine the impact that the type, volume, and ratios of different intraoperative fluids administered has upon postoperative extubation status. A secondary analysis was performed to evaluate the association between delayed postoperative extubation and in-hospital complications and length of ICU and hospital stay. We hypothesized that patients receiving increased amounts of crystalloids during multilevel spine surgery would be at risk for delayed postoperative extubation and that delayed postoperative extubation would be associated with increased postoperative complications and prolonged hospital stay. METHODS Study Design and Setting A retrospective chart review of electronic medical records of patients undergoing elective spine fusion procedures of the thoracic and/or lumbar spine from 2012 to 2015 at a single tertiary care university hospital was performed. Participants Inclusion criteria were age ≥ 18 yr and fusion ≥ 4 levels in the thoracic and/or lumbar spine. Patients with cervical spine procedures, thoracotomy, and procedures performed for acute trauma, tumor or infection were excluded from the study, due to the confounding impact these procedures have upon pulmonary function and postoperative airway management. Institutional review board approval was obtained prior to study initiation. Being a retrospective study, patient consent was exempted for IRB approval. Outcome Measurements Patients were classified according to the immediate postoperative extubation status: (1) immediate extubation group (IMEX; extubation in the operating room [OR] or post-anesthesia care unit [PACU]) and (2) delayed extubation group (DEX; extubation outside the OR/PACU). Estimated blood volume (EBV) was calculated for each patient using the formula: EBV = 70 x body weight (kg), as previously recommended, and patients were stratified into 3 groups based on increasing amount of estimated intraoperative blood volume loss (EBVL; Group 1 ≤ 15%, Group 2 = 15%-30% and Group3 ≥ 30% EBVL).20 Data Collection Patient data evaluated included patient demographics (age, gender, body mass index [BMI], Charlson co-morbidity index [CCI], ASA Grade, and Malampatti score)21; operative details (estimated blood loss [EBL], operative duration, instrumentation levels, type and number of spine osteotomies, interbody fusions). Outcome variables included length of hospital and ICU stay, and postoperative in-hospital major and minor complications, as previously recommended.2 Intraoperative fluid data analyzed included volume of crystalloids (Ringer lactate, normal saline, dextrose), colloids (hydroxylethyl starch, albumin), noncell saver blood products (NCSB; including packed red blood cells [PRBC], platelets, fresh frozen plasma, cryoprecipitate), and cell saver blood administered. In order to quantify and control for the magnitude of surgical procedure performed, we calculated the surgical invasiveness index (SII) for each patient as previously described by Mirza et al.22 The SII provides a value of one unit for each surgical component performed at each vertebra, and a final score is obtained by summing the different procedures performed at each vertebra. The individual surgical components include: (1) anterior decompression: number of vertebra requiring partial or complete Excision of body or the disc if excised from anterior approach; (2) anterior instrumentation: number of vertebra that have screws/plate/cage attached to the body regardless of approach; (3) anterior fusion: number of vertebra that have graft material attached to/replacing the vertebral body regardless of approach; (4) posterior decompression: number of vertebra requiring laminectomy or foraminotomy or discectomy if excised from posterior approach; (5) posterior instrumentation: Number of vertebra having screws/hooks/wires attached to posterior elements; and (6) posterior fusion: number of vertebra that have graft material on their lamina/facets or transverse processes. Sample Size To determine the size of the study population, we performed a power analysis using an alpha (likelihood of Type I error) of 5% and a power of 95% and the study sample was determined to be 250. The variables used to calculate the necessary sample size included: age, blood transfused, FFP transfused, EBL, levels fused, number of SPOs, and number of osteotomies, op- time, cell saver, and length of stay. Of the sample sizes generated, we used the larger values. Bias In order to reduce the effect of multiple variables effecting extubation status and to reduce the magnitude of selection bias, patients within the IMEX and DEX groups were PSM, controlling for age, BMI, CCI, ASA grade, EBL, operative time, and SII. The PSM utilized a genetic PSM algorithm (version 5.7-12.4) within the R package MatchIt (version 2.4-21).23,24 Genetic matching matches patients using scalars, or weights, so that exclusions of patients or replacement is not required. Matching was performed using R (version 3.2.3) within R Studio (version 0.99.484, RStudio, Boston, Massachusetts). Statistical Analysis Frequency distributions were determined for demographic, surgical, and outcome variables for patient groups with increasing levels of EBVL and were compared using Chi-square test for categorical and ANOVA for continuous variables. IMEX and DEX groups were compared using independent sample t-tests for continuous and Chi-square test for categorical variables. Variables that were not distributed evenly were analyzed using nonparametric Mann Whitney t-tests. Correlation coefficients were determined between the proportions of crystalloids, colloids, NCSB products, crystalloid: colloid ratios infused and EBL for IMEX and DEX groups using the Pearson's method. A separate analysis for the occurrence of delayed extubation was performed for patients who received a crystalloid: colloid ratio > 3:1 vs patients who received crystalloid: colloid ratio of ≤ 3:1. We chose this ratio for comparison because previous studies have shown that the volume of crystalloids required to maintain the effective intravascular blood volume is 3 times that of colloids.25,26 All statistics were performed by SPSS software (version 21.0, Armonk, New York). Mean values are presented as Mean ± SD and P values < .05 were considered significant for this study. Source of Funding There was no source of funding for the study RESULTS Demographic and Operative Details of All Patients Included in the Study A total of 246 patients (mean age, 64 yr, range 19-86 yr) met the inclusion criteria. The mean BMI was 27.8 (range, 14.6-42.7), the mean CCI was 1.4 (range 0-8), and the mean ASA grade was 2.6 (range 1-4). The diagnostic categories included: multilevel spinal stenosis (n = 52, 21.1%), spinal deformity (n = 158, 64.3%), spondylolisthesis (n = 14, 5.7%), and others (n = 22, 8.9%). The mean number of spinal levels fused was 10.7 (range, 4-17), 131 patients (53.2%) received minimum 1 level interbody fusion in the lumbar spine, and 47 patients (19.1%) received a 3-column spine osteotomy (Table 1). In our cohort, 198 patients were in the IMEX group and 48 patients (19.5%) were in the DEX group. In the DEX group, 26 patients had extubation between 12-24 h, 18 patients had extubation between 24-36 h and 4 patients had extubation beyond 36 h after surgery. Table 1. Demographic and Surgical Parameters of Patients Undergoing Multilevel Thoracic and Lumbar Spine Fusion Procedures Included in This Study Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 1Include proximal junctional kyphosis, hardware failure, and pseudoarthrosis. 2Three-Column osteotomies include vertebral column resection and pedicle subtraction osteotomy. 3surgical invasiveness index calculated as proposed by Mirza et al.22 View Large Table 1. Demographic and Surgical Parameters of Patients Undergoing Multilevel Thoracic and Lumbar Spine Fusion Procedures Included in This Study Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 1Include proximal junctional kyphosis, hardware failure, and pseudoarthrosis. 2Three-Column osteotomies include vertebral column resection and pedicle subtraction osteotomy. 3surgical invasiveness index calculated as proposed by Mirza et al.22 View Large Analysis of patients according to increasing EBVL demonstrated that patients in Group 3 (n = 136) were older and had greater SII than patients in Groups 1 (n = 42) and 2 (n = 68; P < .001; Table 2). Group 3 received greater volume of crystalloids and NCSB compared to Groups 1 and 2 (P < .001; Table 2). Group 3 had greater number of patients with delayed extubation (43/136, 31.6%), compared to Group 1 (1/42, 2.4%; P < .001) and Group 2 (4/68, 5.9%; P < .001). Group 3 had longer duration of ICU stay (2.1 vs 1.0 vs 0.6 d; P < .001), longer duration of hospital stay (7.6 vs 6.4 vs 6.1 d; P < .01), and greater in-hospital complication rates compared to Groups 1 and 2, respectively. Table 2. Comparison of Patient Groups Categorized Based on Increasing EBVL During Multilevel Thoracolumbar Fusion Procedures1 Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood, LOS- hospital length of stay. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin. NCSB = pRBC + FFP + platelets + cryoprecipitate. 4Early complications categorized as major and minor as recommended.2 5P value in bold represents significance (One way ANOVA). 6a- significance between groups I and II, b- significance between groups II and III, c- significance between groups I and III. View Large Table 2. Comparison of Patient Groups Categorized Based on Increasing EBVL During Multilevel Thoracolumbar Fusion Procedures1 Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood, LOS- hospital length of stay. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin. NCSB = pRBC + FFP + platelets + cryoprecipitate. 4Early complications categorized as major and minor as recommended.2 5P value in bold represents significance (One way ANOVA). 6a- significance between groups I and II, b- significance between groups II and III, c- significance between groups I and III. View Large Propensity Score Matched Analysis of Volume and Type of Intraoperative Fluids Administered in Patients in IMEX and DEX Groups The weights calculated for the propensity scores for IMEX group ranged from 0.163 to 19.83 with a SD of 2.68. The distribution is as follows: 0.163 (n = 26), 0.176 (n = 25), 0.208 (n = 41), 0.254 (n = 19), 0.416 (n = 9), 0.508 (n = 8), 0.654 (n = 23), 0.763 (n = 15), 0.915 (n = 5), 1.144 (n = 6), 1.526 (n = 9), n = 2 for 2.28, 5.49, 11.44, 19.83, and n = 1 for 1.30, 1.68, 3.81, 4.994, 10.07, and 16.93. PSM analysis of DEX and IMEX demonstrated that, DEX had increased volume of PRBC transfused (939 vs 744 ml, P = .009), greater NCSB infused (1289 vs 937 ml, P = .003), and greater crystalloid: colloid ratios (8.5 ± 6.4 vs 6.8 ± 4.0, P = .03) than IMEX, respectively (Table 3). Total volume of crystalloids, colloids and total fluids infused for IMEX and DEX were similar (P > .05). Table 3. Propensity Score Matched Analysis of Patient Demographics, Surgical Factors and Intraoperative Fluids Among Patients With Immediate vs Delayed Extubation Following Multilevel Thoracolumbar Fusion Procedures1 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin, NCSB = pRBC + FFP + platelets + cryoprecipitate, Total intraoperative fluids = crystalloids + colloids + NCSB products + cell saver blood. 4P value in bold represents significance. 5Crystalloid: colloid ratio was calculated for 188 patients only as 58 patients did not receive colloids and were excluded for this analysis. View Large Table 3. Propensity Score Matched Analysis of Patient Demographics, Surgical Factors and Intraoperative Fluids Among Patients With Immediate vs Delayed Extubation Following Multilevel Thoracolumbar Fusion Procedures1 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin, NCSB = pRBC + FFP + platelets + cryoprecipitate, Total intraoperative fluids = crystalloids + colloids + NCSB products + cell saver blood. 4P value in bold represents significance. 5Crystalloid: colloid ratio was calculated for 188 patients only as 58 patients did not receive colloids and were excluded for this analysis. View Large Early Postoperative Complications in IMEX and DEX Groups A total of 69 complications occurred in 246 patients with an overall complication rate of 28%. Fifty-eight patients (23%) had minimum 1 complication and 31 patients (12.3%) had minimum 1 major complication. The mean ICU stay was 2.4 d (range, 0-23) and the mean hospital length of stay was 7.8 days (range, 3-24) for the entire cohort. DEX group had longer ICU (4.0 vs 1.0 d, P < .001) and longer hospital stay (8.9 vs 6.9 d, P = .006) than IMEX (Table 4). DEX had greater cardiac complications (12.5% vs 4%, P = .03), pulmonary complications (18% vs 5%, P = .04), surgical site infections (8.3% vs 1.5%, P = .02) and greater total complication rates than IMEX (50 vs 17.1%, P < .001), respectively. One death occurred in the DEX group due to postoperative pulmonary edema. Table 4. Comparison of Early Postoperative Events and Complications Among Patients With Immediate vs Delayed Extubation Groups Following Complex Thoracolumbar Surgical Procedures Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 1P values in bold represent significance. 2Major complications categorized according to criteria given by Glassman et al.2 3Cardiac complications include congestive heart failure, myocardial infarction, and cardiac arrhythmia. 4Pulmonary complications include airway edema, pulmonary edema, pneumonia, pleural effusion, and ARDS. 5Neurological complications include delirium, severe headache, motor, or sensory deficit. 6Include pressure sores, deep venous thrombosis, and urinary retention requiring catheterization and atelectasis. View Large Table 4. Comparison of Early Postoperative Events and Complications Among Patients With Immediate vs Delayed Extubation Groups Following Complex Thoracolumbar Surgical Procedures Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 1P values in bold represent significance. 2Major complications categorized according to criteria given by Glassman et al.2 3Cardiac complications include congestive heart failure, myocardial infarction, and cardiac arrhythmia. 4Pulmonary complications include airway edema, pulmonary edema, pneumonia, pleural effusion, and ARDS. 5Neurological complications include delirium, severe headache, motor, or sensory deficit. 6Include pressure sores, deep venous thrombosis, and urinary retention requiring catheterization and atelectasis. View Large Analysis of Fluid Proportions and Crystalloid: Colloid Ratios Infused with Increasing EBL in IMEX and DEX Groups Analysis of blood products administered demonstrated an increase in the volume of NCSB products infused with increasing EBL for both IMEX (R = 0.47, P < .001) and DEX (R = 0.35, P = .01). However, with increasing EBL and with increasing NCSB products infused, IMEX had a significant decrease in the proportion of crystalloids administered (R = –0.5, P < .001). Conversely, with increasing EBL and increasing NCSB transfusion, DEX did not demonstrate a significant reduction in the proportion of crystalloids infused (R = –0.27, P = .09, Figure 1). Figure 1. View largeDownload slide Graph showing changes in fluid proportions with increasing EBL. It can be seen that with increasing EBL, the NCSB proportion increases linearly in both IMEX and DEX groups. However, this is accompanied by a significant reduction in the crystalloid proportion in the IMEX group, whereas, the crystalloid proportion relatively remains unchanged in the DEX group. Figure 1. View largeDownload slide Graph showing changes in fluid proportions with increasing EBL. It can be seen that with increasing EBL, the NCSB proportion increases linearly in both IMEX and DEX groups. However, this is accompanied by a significant reduction in the crystalloid proportion in the IMEX group, whereas, the crystalloid proportion relatively remains unchanged in the DEX group. Analysis of crystalloid: colloid administered according to EBL revealed that, in the IMEX group, the ratios of crystalloid: colloid infused decreased with an increase in EBL (R = –0.42, P = .04), whereas, the DEX group demonstrated an increased crystalloid: colloid ratio with an increase in EBL in the DEX group (R = 0.47, P < .001, Figure 2). Figure 2. View largeDownload slide Graph showing trends in crystalloid: colloid ratio infused with increasing estimated blood loss in immediate (IMEX) and delayed (DEX) extubation groups: it can be seen that with increasing blood loss, the crystalloid: colloid infusion ratio increases linearly in the IMEX group (R = 0.42, P = .04) whereas, it decreases in the DEX group (R = –0.47, P < .001). Figure 2. View largeDownload slide Graph showing trends in crystalloid: colloid ratio infused with increasing estimated blood loss in immediate (IMEX) and delayed (DEX) extubation groups: it can be seen that with increasing blood loss, the crystalloid: colloid infusion ratio increases linearly in the IMEX group (R = 0.42, P = .04) whereas, it decreases in the DEX group (R = –0.47, P < .001). Out of 168 patients who received a crystalloid: colloid ratio > 3:1, 44 patients underwent delayed extubation (26%), whereas, none of the 20 patients who received a crystalloid: colloid infusion ratio ≤ 3:1 had delayed extubation (P = .009). DISCUSSION We present a retrospective study on the impact of intraoperative fluids on immediate postoperative extubation status for patients undergoing multilevel thoracic and/or lumbar spine procedures. Not surprisingly, we found that that with increasing complexity of the surgical procedure and increasing blood loss, patients received larger volume of intraoperative fluids, and had increased rates of delayed extubation, greater in-hospital complications and prolonged ICU and hospital stays. However, after controlling for patient demographics, comorbidities, and invasiveness of surgical procedures via PSM analysis, our results indicated that increased volume of NCSB products administered and increased crystalloid: colloid ratios infused are associated with delayed extubation. We also found that, with increasing EBL and increasing NSCB product transfusion, patients that did not have a proportionate decrease in the volume of crystalloids administered were at risk for delayed extubation. Very few studies have evaluated the impact of intraoperative fluid resuscitation on postoperative extubation status and early outcomes following spine procedures.16-19 Li e al18 found that the factors associated with delayed extubation following thoracic and lumbar spine surgeries included operative time, EBL, volume of intraoperative crystalloids and blood products. Similarly, Anastasian et al16 reported that in addition to the above parameters, ASA grade, extent of surgery, and the surgical end time were associated with decision to delay extubation following multilevel spine surgeries. However, these studies are subjected to selection and confounding bias due to the effect of multiple known and unknown demographic and surgical factors on extubation status. We performed PSM analysis to improve patient selection methods and reduce confounding covariates for patients that had immediate or delayed extubation. Increased duration of soft tissue trauma with prolonged surgeries can initiate a cascade of systemic inflammatory response thereby altering the vascular hemodynamics and coagulation profile leading to increased vascular permeability.6 Optimal fluid administration during such events is crucial as excess fluids administered can lead to hemodilution, acidosis, hypothermia, third spacing, abdominal compartment syndrome, respiratory distress syndrome, and multiorgan failure.27-29 This is especially true with crystalloid infusion since, crystalloids are low molecular weight salt solutions as compared to some of the high molecular weight complex colloid solutions. Also, the negatively charged endothelial glycocalyx acts as a strong resistance for permeation of colloids.30 With increasing blood loss; patients tend to receive an increased volume of blood products in order to maintain the oxygen carrying capacity. Since most of the blood products infused remain intravascular, there is a reciprocal reduction in the need for other types of fluids, especially crystalloids to maintain the effective intravascular fluid volume and blood pressure. This explains our findings that with increasing EBL, as patients tend to receive increased proportion of blood products, prompt extubation was possible when patients received a proportionate reduction in the infusion of crystalloids. The ratio of crystalloids: colloids administered during elective noncardiac surgeries have ranged from 0.89 to 4.74, with a trend of persistent reduction over the years.31 Previous studies have shown that 25% of crystalloids infused remain intravascular, whereas, this proportion increases to 75% for colloids.25,26 Therefore, theoretically, the volume of crystalloids required to maintain the same target of intravascular volume would be 3 times that of colloids. This was the basis of our analysis comparing patients who received a crystalloid: colloid ratio > 3:1 with those who received crystalloid: colloid ratios ≤ 3:1. Accordingly, our results indicate patients infused with crystalloid: colloid infusion ratio > 3:1 had a greater occurrence of delayed extubation than patients receiving crystalloid: colloid ratio ≤ 3:1. In our cohort, 58 patients received only crystalloids and were eliminated for the crystalloid: colloid analysis, which might have potential bias in the results. Unfortunately, due to a nonstandard protocol on fluid resuscitation strategies, different anesthesiologist at our institution use different fluid resuscitative measures intraoperatively and there were patients in whom, colloids were not used. Out of these, 54 patients (93%) had immediate extubation. The possible explanation for this observation is that in this group of patients the mean EBL (1.27L), operative time (320 min), cell saver use (314.5ml), and the SII (18.6) were considerably lower than that of the entire cohort of IMEX patients (Table 3), respectively. Previous studies have shown that the effectiveness of crystalloids or colloids in maintaining the intravascular blood volume depends on the existing degree of hypovolemia.32 With relatively mild volume depletion, crystalloids and colloids have almost equal efficacy in maintaining the intraoperative fluid volume. However, with profound hypovolemia, colloids are 4 times more efficacious in maintaining the fluid volume as compared to crystalloids.32,33 In our study, we found that, with increasing EBL, there was a progressive reduction in the crystalloid: colloid ratios infused in patients who underwent prompt extubation. Conversely, patients in the DEX group received increasing ratios of crystalloid: colloid as blood loss increased. These findings suggest that physicians should have a low threshold for using colloids, rather than high volumes of crystalloid, to maintain intravascular volume in the event of large blood loss associated with multilevel spine fusion surgery whenever feasible. The early postoperative complication rate of 28% reported in our study is lower than that described previously for complex spine surgeries, as previously reported rates range from 48.5%-77%.3,34,35 This may be due to the retrospective nature, lack of objective assessment in reporting specific adverse events and focus on major medical complications in our study. In a recent study, Soroceanu et al4 reported an early perioperative medical complication rate of 26.8% in 448 patients undergoing surgery for adult spinal deformities, which is similar to our study. Importantly, we found that patients who underwent delayed extubation had higher cardiac and pulmonary complications and higher surgical site infections than patients receiving immediate extubation. The association between delayed extubation and postoperative complications is multifactorial and has been previously described, including prolonged stasis and poor mobility, prolonged ICU stay, risk for postextubation aspiration pneumonia, venous air embolism, and cardiac arrest. 9,36-39 Although our study is retrospective, we have reported the results of a PSM analyses in an attempt to reduce the effects of confounding variables within our cohort, partially mimicking the effects of randomization. The incorporation of a validated SII has allowed us to compare and control for the surgical elements as a single objective variable and thereby clearly associate the early postoperative outcomes to intraoperative fluid management strategies. However, our study is not without limitations. Limitations Being a single center study, the anesthetic protocol followed for our patients may not represent universal standards. The decision of fluid resuscitation was based on individual anesthesiologist's preference based on the ongoing hemodynamic status of the patient. Similarly, the decision to extubate the patient was based on the patient's co-morbidities, ASA grade, acid-base status, O2 saturation, hemodynamic stability, duration of the procedure, blood loss, and anticipated airway edema and might have been nonstandard. Also, several other parameters like body temperature, acid-base status, mean arterial pressure, anesthetic handoffs, and case end time have not been incorporated, which may have direct implications. Similarly, we did not perform analysis between administration of colloids and postoperative coagulation parameters and renal function tests to determine the effect of colloids. Nonetheless, our results provide data to support the effects of intraoperative fluid management on perioperative outcomes following complex spine surgical procedures. Future research using randomized controlled trials will facilitate formulating guidelines to incorporate fluid management strategies in protocols for managing patients with complex pathologies such as those previously described.40-42 CONCLUSION Our results indicate that increased volume of NCSB products administered and high crystalloid: colloid ratio infused intraoperatively is independently associated with delayed extubation following multilevel spine surgeries. With increasing blood loss, immediate postoperative extubation is facilitated when the proportion of crystalloid fluids administered is proportionately reduced with respect to the total fluids infused. Additionally, 27% of patients who received crystalloid: colloid infusion ratio > 3:1 underwent delayed extubation, whereas no patient underwent delayed extubation when the crystalloid: colloid infusion ratio was ≤ 3:1. Patients with delayed extubation had increased cardiac and pulmonary complications, increased surgical site infections and prolonged ICU and hospital length of stay. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Martin BI , Turner JA , Mirza SK , Lee MJ , Comstock BA , Deyo RA . Trends in health care expenditures, utilization, and health status among US adults with spine problems, 1997-2006 . Spine . 2009 ; 34 ( 19 ): 2077 – 2084 . Google Scholar CrossRef Search ADS PubMed 2. Glassman SD , Hamill CL , Bridwell KH , Schwab FJ , Dimar JR , Lowe TG . The impact of perioperative complications on clinical outcome in adult deformity surgery . 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J Stat Soft. 2011 ; 42 ( 11 ): 1 – 26 . Google Scholar CrossRef Search ADS 24. Ho DE , Imai K , King G , Stuart E . Matching as nonparametric preprocessing for reducing model dependence in parametric causal inference . Polit Anal . 2007 ; 15 ( 3 ): 199 – 236 . Google Scholar CrossRef Search ADS 25. Balogh Z , McKinley BA , Holcomb JB et al. Both primary and secondary abdominal compartment syndrome can be predicted early and are harbingers of multiple organ failure . The Journal of Trauma: Injury, Infection, and Critical Care 2003 ; 54 ( 5 ): 848 – 861 . Google Scholar CrossRef Search ADS 26. Madigan MC , Kemp CD , Johnson JC , Cotton BA . Secondary abdominal compartment syndrome after severe extremity injury: are early, aggressive fluid resuscitation strategies to blame? J Trauma. 2008 ; 64 ( 2 ): 280 – 285 . Google Scholar CrossRef Search ADS PubMed 27. Cotton BA , Guy JS , Morris JA , Abumrad NN . The cellular, metabolic, and systemic consequences of aggressive fluid resuscitation strategies . Shock . 2006 ; 26 ( 2 ): 115 – 121 . Google Scholar CrossRef Search ADS PubMed 28. Wiedemann HP , Wheeler AP , Bernard GR et al. Comparison of two fluid-management strategies in acute lung injury . N Engl J Med . 2006 ; 354 ( 24 ): 2564 – 2575 . Google Scholar CrossRef Search ADS PubMed 29. Wafaisade A , Wutzler S , Lefering R et al. Drivers of acute coagulopathy after severe trauma: a multivariate analysis of 1987 patients . Emerg Med J. 2010 ; 27 ( 12 ): 934 – 939 . Google Scholar CrossRef Search ADS PubMed 30. VanTeeffelen JW , Brands J , Stroes ES , Vink H . Endothelial glycocalyx: sweet shield of blood vessels . Trends Cardiovasc Med. 2007 ; 17 ( 3 ): 101 – 105 . Google Scholar CrossRef Search ADS PubMed 31. Orbegozo CD , Gamarano BT , Njimi H , Vincent J-L . Crystalloids versus colloids . Anesth Analg . 2015 ; 120 ( 2 ): 389 – 402 . Google Scholar CrossRef Search ADS PubMed 32. Roger C , Muller L , Deras P et al. Does the type of fluid affect rapidity of shock reversal in an anaesthetized-piglet model of near-fatal controlled haemorrhage? A randomized study . Br J Anaesth. 2014 ; 112 ( 6 ): 1015 – 1023 . Google Scholar CrossRef Search ADS PubMed 33. Zornow MH , Prough DS . Fluid management in patients with traumatic brain injury . New Horiz. 1995 ; 3 ( 3 ): 488 – 498 . Google Scholar PubMed 34. Karstensen S , Bari T , Gehrchen M , Street J , Dahl B . Morbidity and mortality of complex spine surgery: a prospective cohort study in 679 patients validating the Spine AdVerse Event Severity (SAVES) system in a European population . Spine J . 2016 ; 16 ( 2 ): 146 – 153 . Google Scholar CrossRef Search ADS PubMed 35. Klineberg EO , Passias PG , Jalai CM et al. Predicting extended length of hospital stay in an adult spinal deformity surgical population . Spine . 2015 ; 41 ( 13 ): E798 – 805 (Dec 14) doi:10.1097/BRS.0000000000001391 Google Scholar CrossRef Search ADS 36. De Larminat V , Montravers P , Dureuil B , Desmonts JM . Alteration in swallowing reflex after extubation in intensive care unit patients . Crit Care Med. 1995 ; 23 ( 3 ): 486 – 490 . Google Scholar CrossRef Search ADS PubMed 37. Kim MJ , Park YH , Park YS , Song YH . Associations between prolonged intubation and developing post-extubation dysphagia and aspiration pneumonia in non-neurologic critically ill patients . Ann Rehabil Med . 2015 ; 39 ( 5 ): 763 – 771 . Google Scholar CrossRef Search ADS PubMed 38. Brown J , Rogers J , Soar J . Cardiac arrest during surgery and ventilation in the prone position: A case report and systematic review . Resuscitation . 2001 ; 50 ( 2 ): 233 – 238 . Google Scholar CrossRef Search ADS PubMed 39. Albin MS , Ritter RR , Pruett CE , Kalff K . Venous air embolism during lumbar laminectomy in the prone position . Anesth Analg . 1991 ; 73 ( 3 ): 346 – 349 . Google Scholar CrossRef Search ADS PubMed 40. Hart RA , Dupaix JP , Rusa R , Kane MS , Volpi JD . Reduction of airway complications with fluid management protocol in patients undergoing cervical decompression and fusion across the cervicothoracic junction . Spine . 2013 ; 38 ( 18 ): E1135 – E1140 . Google Scholar CrossRef Search ADS PubMed 41. Sethi RK , Pong RP , Leveque JC , Dean TC , Olivar SJ , Rupp SM . The Seattle spine team approach to adult deformity surgery: a systems-based approach to perioperative care and subsequent reduction in perioperative complication rates . Spine Deform . 2014 ; 2 ( 2 ): 95 – 103 . Google Scholar CrossRef Search ADS PubMed 42. Halpin RJ , Sugrue PA , Gould RW et al. Standardizing care for high-risk patients in spine surgery . Spine . 2010 ; 35 ( 25 ): 2232 – 2238 . Google Scholar CrossRef Search ADS PubMed COMMENTS In this study, the authors examine the impact of differing strategies for intraoperative fluid resuscitation of patients undergoing multi-level thoracic and lumbar spine operations. They found that patients receiving high volumes of crystalloids were at increased risk for delayed extubation, and that in patients who received a crystalloid to colloid infusion ratio of ≤ 3, all patients were able to be extubated without delay. Patients undergoing multi-level spine operations are at risk for delayed extubation due to the often prolonged operative times and high fluid volume shifts.1 Previous studies have found a variety of risk factors for delayed extubation including blood transfusion, blood loss, and baseline anesthetic risk.1,2Given the severity of complications that may be associated with prolonged intubation,3,4 such information has value to both neurosurgeons and the anesthesiologists who participate in the care of these patients. The present article is unique in its use of propensity matching in order to control for various possible confounders, and their findings support previous studies suggesting that large volume fluid shifts (especially when aggressive resuscitation is performed using crystalloids) can result in a delay in extubation.3,4 This study is not without limitations, however. The authors point out that resuscitation and extubation decisions, while guided by objective criteria such as oxygen saturation and blood loss, were ultimately the discretion of the anesthesiologist – a factor that was not controlled for and could be a significant source of bias. Before the data from this study can be used to inform care decisions, the findings must be validated. Ideally, this would be done in a prospective manner, with an established, uniform set of criteria for both fluid administration and extubation. Regardless, this article again highlights the importance of appropriate intraoperative anesthesia and fluid management to minimize the risks to patients undergoing complex spine operations. Jian Guan Joel D. MacDonald Salt Lake City, Utah 1. Anastasian ZH Gaudet JG Levitt LC , et al . Factors that correlate with the decision to delay extubation after multilevel prone spine surgery . J Neurosurg Anesthesiol . 2014 ; 26 : 167 – 171 . Google Scholar CrossRef Search ADS PubMed 2. Li F Gorji R Tallarico R Dodds C Modes K Mangat S Yang ZJ . Risk factors for delayed extubation in thoracic and lumbar spine surgery: a retrospective analysis of 135 patients . J Anesth . 2014 ; 28 ( 2 ): 161 – 166 . Google Scholar CrossRef Search ADS PubMed 3. Fagon JY Chastre J Domart Y Trouillet JL Pierre J Darne C Gibert C . Nosocomial pneumonia in patients receiving continuous mechanical ventilation. Prospective analysis of 52 episodes with use of a protected specimen brush and quantitative culture techniques . Am Rev Respir Dis . 1989 ; 139 ( 4 ): 877 – 884 . Google Scholar CrossRef Search ADS PubMed 4. Liu CC Livingstone D Dixon E Dort JC . Early versus late tracheostomy: a systematic review and meta-analysis . Otolaryngol Head Neck Surg . 2015 ; 152 ( 2 ): 219 – 27 . Google Scholar CrossRef Search ADS PubMed The authors provide an interesting retrospective analysis of intraoperative fluid administration and its impact on extubation. Despite the limitations of the study design, the findings agree with generally held observational beliefs that increasing surgical time, blood loss, and crystalloid administration are associated with prolonged intubation. In this cohort, a total of 246 patients were included. The authors found that increased administration of crystalloid to colloid ratio is independently associated with delayed extubation. They also suggest that with increasing EBL, a reduction of crystalloids may allow for early extubation. Carlos David Burlington, Massachusetts The authors present a single-institution analysis to assess the impact of different intraoperative fluid administration strategies on postoperative extubation following elective multi-level thoracic and lumbar spinal fusion. Following a propensity score matching for a number of baseline characteristics, the authors found that patients receiving a delayed extubation had a higher crystalloid to colloid administration ratio and higher use of non-cell saver blood products. Furthermore, upon secondary analysis, they found that delayed extubation was associated with a higher rate of postoperative complications. The authors are to be commended for a rigorous analysis as these are important findings with potential ramifications for spinal neuroanesthesia practice. Propensity score matching helped address the influence of several important confounding covariates, but propensity score matching adds its own bias by removing subjects from the analysis. The crystalloid to colloid ratio findings are likely a result of this propensity score bias. The differences between the immediate and delayed extubation groups in mean crystalloid was only 5800 ml versus 6100 ml and in mean colloid only 856 ml versus 811 ml. Is the reader to conclude that an extra 45 ml of colloid if not delivered with 300 ml of crystalloid will result in significantly worse outcomes and complications? Most likely, the crystalloid colloid ratio would not have been significant on multi-variable regression analysis, making this part of the result a potential example of statistical bias. The study results that would continue to hold significance are that blood transfusions are significantly associated with delayed extubation and longer length of stay. Hopefully, the study team will continue to assess the important findings of their analysis in larger cohorts. Mohamad Bydon Rochester, Minnesota Copyright © 2018 by the Congress of Neurological Surgeons This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Neurosurgery Oxford University Press

The Impact of Different Intraoperative Fluid Administration Strategies on Postoperative Extubation Following Multilevel Thoracic and Lumbar Spine Surgery: A Propensity Score Matched Analysis

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Congress of Neurological Surgeons
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Copyright © 2018 by the Congress of Neurological Surgeons
ISSN
0148-396X
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1524-4040
D.O.I.
10.1093/neuros/nyy226
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Abstract

Abstract BACKGROUND Patients undergoing multilevel spine surgery are at risk for delayed extubation. OBJECTIVE To evaluate the impact of type and volume of intraoperative fluids administered during multilevel thoracic and/or lumbar spine surgery on postoperative extubation status. METHODS Retrospective evaluation of medical records of patients ≥ 18 yr undergoing ≥ 4 levels of thoracic and/or lumbar spine fusions was performed. Patients were organized according to postoperative extubation status: immediate (IMEX; in OR/PACU) or delayed (DEX; outside OR/PACU). Propensity score matched (PSM) analysis was performed to compare IMEX and DEX groups. Volume, proportion, and ratios of intraoperative fluids administered were evaluated for the associated impact on extubation status. RESULTS A total of 246 patients (198 IMEX, 48 DEX) were included. PSM analysis demonstrated that increased administration of non-cell saver blood products (NCSB) and increased ratio of crystalloid: colloids infused were independently associated with delayed extubation. With increasing EBL, IMEX had a proportionate reduction in crystalloid infusion (R = –0.5, P < .001), while the proportion of crystalloids infused remained relatively unchanged for DEX (R = –0.27; P = .06). Twenty-six percent of patients receiving crystalloid: colloid ratio > 3:1 had DEX compared to none of those receiving crystalloid: colloid ratio ≤ 3:1 (P = .009). DEX had greater cardiac and pulmonary complications, surgical site infections and prolonged intensive care unit and hospital stay (P < .05). CONCLUSION PSM analysis of patients undergoing multilevel thoracic and/or lumbar spine fusion demonstrated that increased administration of crystalloid to colloid ratio is independently associated with delayed extubation. With increasing EBL, a proportionate reduction of crystalloids facilitates early extubation. Delayed extubation, Fluid resuscitation, Early complications, Multilevel, Spinal Fusion, Surgical invasiveness ABBREVIATIONS ABBREVIATIONS ASA American Society of Anesthesiologists BMI body mass index CCI Charlson co-morbidity index DEX delayed extubation EBL estimated blood loss EBV Estimated blood volume EBVL estimated intraoperative blood volume loss IMEX immediate extubation group ICU intensive care unit NCSB non-cell saver blood OR operating room PRBC packed red blood cells PACU post-anesthesia care unit PSM Propensity score matched SII surgical invasiveness index Improved understanding of spine anatomy and advances in fusion techniques have enabled surgeons to more commonly perform complex spine procedures, as demonstrated by increasing rates of multilevel spine fusion procedures over the past decade.1 However, multilevel spine fusion procedures are associated with high complication rates.2-4 These procedures often involve large incisions with extensive soft tissue dissection and periosteal exposure over large areas of the spine, which triggers a massive systemic inflammatory response.5 The combination of soft tissue trauma, systemic inflammation, and prolonged intraoperative anesthesia can alter the patient's vascular integrity, thereby impacting fluid requirements, fluid responsiveness, and generate large intra and extravascular fluid shifts.6 These fluid shifts in association with prone surgical positioning can cause delayed postoperative extubation. Prolonged endotracheal intubation is associated with a multitude of complications including airway and pulmonary edema, pneumonia, stasis ulcers, wound dehiscence, and prolonged intensive care unit (ICU) and hospital length of stay.7-10 Optimal intraoperative fluid replacement protocols for surgeries that involve large blood loss and prolonged surgical times remain controversial.11-13 According to a recent meta-analysis, there is currently insufficient evidence to suggest advantages of administering one type of fluids over another during elective noncardiac procedures.14 Synthetic colloids are often administered since they can maintain intravascular fluid volume and regional tissue perfusion more efficiently than crystalloids. However, there has been reported a potential increased risk of renal failure and coagulation disorders with the use of intraoperative colloid solutions.15 With respect to spine surgery, few studies have examined the role of intraoperative fluid administration on postoperative extubation status.16-19 Anastasian et al16 reported that age, American Society of Anesthesiologists (ASA) Grade, procedure duration, magnitude of surgery, total crystalloid and blood volumes administered, and procedure end-time correlated with delayed extubation after multilevel spine surgery. Similarly, Nahtomi-Shick et al17 reported that increased intraoperative administration of blood products and crystalloids was associated with increased ICU length of stay for patients undergoing spinal surgeries; however, the authors did not evaluate postoperative extubation status or reasons for prolonged care. Consequently, the impact that the type and proportion of intraoperative fluids administered during multilevel spine surgery has upon postoperative extubation remains uncertain. The objective of this study was to perform a propensity score matched (PSM) analysis of patients undergoing multilevel thoracic and/or lumbar spine fusion procedures to determine the impact that the type, volume, and ratios of different intraoperative fluids administered has upon postoperative extubation status. A secondary analysis was performed to evaluate the association between delayed postoperative extubation and in-hospital complications and length of ICU and hospital stay. We hypothesized that patients receiving increased amounts of crystalloids during multilevel spine surgery would be at risk for delayed postoperative extubation and that delayed postoperative extubation would be associated with increased postoperative complications and prolonged hospital stay. METHODS Study Design and Setting A retrospective chart review of electronic medical records of patients undergoing elective spine fusion procedures of the thoracic and/or lumbar spine from 2012 to 2015 at a single tertiary care university hospital was performed. Participants Inclusion criteria were age ≥ 18 yr and fusion ≥ 4 levels in the thoracic and/or lumbar spine. Patients with cervical spine procedures, thoracotomy, and procedures performed for acute trauma, tumor or infection were excluded from the study, due to the confounding impact these procedures have upon pulmonary function and postoperative airway management. Institutional review board approval was obtained prior to study initiation. Being a retrospective study, patient consent was exempted for IRB approval. Outcome Measurements Patients were classified according to the immediate postoperative extubation status: (1) immediate extubation group (IMEX; extubation in the operating room [OR] or post-anesthesia care unit [PACU]) and (2) delayed extubation group (DEX; extubation outside the OR/PACU). Estimated blood volume (EBV) was calculated for each patient using the formula: EBV = 70 x body weight (kg), as previously recommended, and patients were stratified into 3 groups based on increasing amount of estimated intraoperative blood volume loss (EBVL; Group 1 ≤ 15%, Group 2 = 15%-30% and Group3 ≥ 30% EBVL).20 Data Collection Patient data evaluated included patient demographics (age, gender, body mass index [BMI], Charlson co-morbidity index [CCI], ASA Grade, and Malampatti score)21; operative details (estimated blood loss [EBL], operative duration, instrumentation levels, type and number of spine osteotomies, interbody fusions). Outcome variables included length of hospital and ICU stay, and postoperative in-hospital major and minor complications, as previously recommended.2 Intraoperative fluid data analyzed included volume of crystalloids (Ringer lactate, normal saline, dextrose), colloids (hydroxylethyl starch, albumin), noncell saver blood products (NCSB; including packed red blood cells [PRBC], platelets, fresh frozen plasma, cryoprecipitate), and cell saver blood administered. In order to quantify and control for the magnitude of surgical procedure performed, we calculated the surgical invasiveness index (SII) for each patient as previously described by Mirza et al.22 The SII provides a value of one unit for each surgical component performed at each vertebra, and a final score is obtained by summing the different procedures performed at each vertebra. The individual surgical components include: (1) anterior decompression: number of vertebra requiring partial or complete Excision of body or the disc if excised from anterior approach; (2) anterior instrumentation: number of vertebra that have screws/plate/cage attached to the body regardless of approach; (3) anterior fusion: number of vertebra that have graft material attached to/replacing the vertebral body regardless of approach; (4) posterior decompression: number of vertebra requiring laminectomy or foraminotomy or discectomy if excised from posterior approach; (5) posterior instrumentation: Number of vertebra having screws/hooks/wires attached to posterior elements; and (6) posterior fusion: number of vertebra that have graft material on their lamina/facets or transverse processes. Sample Size To determine the size of the study population, we performed a power analysis using an alpha (likelihood of Type I error) of 5% and a power of 95% and the study sample was determined to be 250. The variables used to calculate the necessary sample size included: age, blood transfused, FFP transfused, EBL, levels fused, number of SPOs, and number of osteotomies, op- time, cell saver, and length of stay. Of the sample sizes generated, we used the larger values. Bias In order to reduce the effect of multiple variables effecting extubation status and to reduce the magnitude of selection bias, patients within the IMEX and DEX groups were PSM, controlling for age, BMI, CCI, ASA grade, EBL, operative time, and SII. The PSM utilized a genetic PSM algorithm (version 5.7-12.4) within the R package MatchIt (version 2.4-21).23,24 Genetic matching matches patients using scalars, or weights, so that exclusions of patients or replacement is not required. Matching was performed using R (version 3.2.3) within R Studio (version 0.99.484, RStudio, Boston, Massachusetts). Statistical Analysis Frequency distributions were determined for demographic, surgical, and outcome variables for patient groups with increasing levels of EBVL and were compared using Chi-square test for categorical and ANOVA for continuous variables. IMEX and DEX groups were compared using independent sample t-tests for continuous and Chi-square test for categorical variables. Variables that were not distributed evenly were analyzed using nonparametric Mann Whitney t-tests. Correlation coefficients were determined between the proportions of crystalloids, colloids, NCSB products, crystalloid: colloid ratios infused and EBL for IMEX and DEX groups using the Pearson's method. A separate analysis for the occurrence of delayed extubation was performed for patients who received a crystalloid: colloid ratio > 3:1 vs patients who received crystalloid: colloid ratio of ≤ 3:1. We chose this ratio for comparison because previous studies have shown that the volume of crystalloids required to maintain the effective intravascular blood volume is 3 times that of colloids.25,26 All statistics were performed by SPSS software (version 21.0, Armonk, New York). Mean values are presented as Mean ± SD and P values < .05 were considered significant for this study. Source of Funding There was no source of funding for the study RESULTS Demographic and Operative Details of All Patients Included in the Study A total of 246 patients (mean age, 64 yr, range 19-86 yr) met the inclusion criteria. The mean BMI was 27.8 (range, 14.6-42.7), the mean CCI was 1.4 (range 0-8), and the mean ASA grade was 2.6 (range 1-4). The diagnostic categories included: multilevel spinal stenosis (n = 52, 21.1%), spinal deformity (n = 158, 64.3%), spondylolisthesis (n = 14, 5.7%), and others (n = 22, 8.9%). The mean number of spinal levels fused was 10.7 (range, 4-17), 131 patients (53.2%) received minimum 1 level interbody fusion in the lumbar spine, and 47 patients (19.1%) received a 3-column spine osteotomy (Table 1). In our cohort, 198 patients were in the IMEX group and 48 patients (19.5%) were in the DEX group. In the DEX group, 26 patients had extubation between 12-24 h, 18 patients had extubation between 24-36 h and 4 patients had extubation beyond 36 h after surgery. Table 1. Demographic and Surgical Parameters of Patients Undergoing Multilevel Thoracic and Lumbar Spine Fusion Procedures Included in This Study Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 1Include proximal junctional kyphosis, hardware failure, and pseudoarthrosis. 2Three-Column osteotomies include vertebral column resection and pedicle subtraction osteotomy. 3surgical invasiveness index calculated as proposed by Mirza et al.22 View Large Table 1. Demographic and Surgical Parameters of Patients Undergoing Multilevel Thoracic and Lumbar Spine Fusion Procedures Included in This Study Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 Demographic parameters Patients undergoing multilevel spine fusion procedures (n = 246) Age (yr) 64.2 ± 12.1 Gender 106 Females (43%) Body mass index (BMI) 27.8 ± 5.1 Previous fusion 108 (44%) Charlson Co-morbidity index (CCI) 1.4 ± 1.5 American society of Anesthesiologist grade (ASA) 2.6 ± 0.7 Malampatti score 1.9 ± 0.7 Diagnostic categories (n, %)  Degenerative spinal stenosis 52 (21.1)  Spinal deformity 158 (54.3)  Spondylolisthesis 14 (5.7)  Others1 22 (8.9) Surgical parameters  Estimated Blood Loss (mL) 3200 ± 1300  Operative time (min) 432 ± 122  No. of fusion levels 10.7 ± 3.8  No. of patients receiving interbody fusion 131 (53.2%)  No. of patients receiving 3-column osteotomy2 47 (19.1%)  Surgical invasiveness index3 24.2 ± 7.6 1Include proximal junctional kyphosis, hardware failure, and pseudoarthrosis. 2Three-Column osteotomies include vertebral column resection and pedicle subtraction osteotomy. 3surgical invasiveness index calculated as proposed by Mirza et al.22 View Large Analysis of patients according to increasing EBVL demonstrated that patients in Group 3 (n = 136) were older and had greater SII than patients in Groups 1 (n = 42) and 2 (n = 68; P < .001; Table 2). Group 3 received greater volume of crystalloids and NCSB compared to Groups 1 and 2 (P < .001; Table 2). Group 3 had greater number of patients with delayed extubation (43/136, 31.6%), compared to Group 1 (1/42, 2.4%; P < .001) and Group 2 (4/68, 5.9%; P < .001). Group 3 had longer duration of ICU stay (2.1 vs 1.0 vs 0.6 d; P < .001), longer duration of hospital stay (7.6 vs 6.4 vs 6.1 d; P < .01), and greater in-hospital complication rates compared to Groups 1 and 2, respectively. Table 2. Comparison of Patient Groups Categorized Based on Increasing EBVL During Multilevel Thoracolumbar Fusion Procedures1 Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood, LOS- hospital length of stay. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin. NCSB = pRBC + FFP + platelets + cryoprecipitate. 4Early complications categorized as major and minor as recommended.2 5P value in bold represents significance (One way ANOVA). 6a- significance between groups I and II, b- significance between groups II and III, c- significance between groups I and III. View Large Table 2. Comparison of Patient Groups Categorized Based on Increasing EBVL During Multilevel Thoracolumbar Fusion Procedures1 Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A Categories of blood loss Parameters Group I (< 15% EBVL) (n = 42) Group II (15-30% EBVL)(n = 68) Group III (> 30% EBVL) (n = 136) P value5 Post Hoc Analysis6 Demographic  Age (yr) 52 ± 20.6 51.7 ± 20.6 59.3 ± 17 .008 c  Basal Metabolic Index (BMI) 27.7 ± 5.2 26.2 ± 6.5 26.8 ± 5.7 .54 N/A  Female (n, %) 15, 35.7% 22, 32.4% 45, 33.1% .93 N/A  Charlson Co-morbidity Index 0.8 ± 1.1 1 ± 1.3 1 ± 1.3 .61 N/A  Malampatti score 1.7 ± 0.8 1.6 ± 0.7 1.7 ± 0.7 .62 N/A  ASA 2.1 ± 0.8 2.2 ± 0.6 2.3 ± 0.6 .45 N/A Surgical  Operative time (min) 322 ± 134 300 ± 110 370 ± 128 .001 b, c  Estimated Blood loss (ml) 493 ± 160 1114 ± 375 3040 ± 1385 < .001 a, b, c  No. of fusion levels 7.2 ± 3.4 8.6 ± 3.6 10.4 ± 3.7 < .001 b, c   3-Column osteotomy (N, %) 1, 2.4% 5, 7.4% 41, 30.1% < .001 N/A  Interbody fusion (N, %) 17, 40.5% 26, 38.2% 88, 64.7% < .001 N/A  Surgical invasiveness index2 23.2 ± 9.3 25.5 ± 10.8 36.2 ± 10.9 < .001 b, c Intraoperative fluids infused (ml)  Ringer Lactate (RL) 2990 ± 1522 3398 ± 1033 4843 ± 1956 < .001 b, c  Normal Saline (NS) 340 ± 1240 350 ± 577 635 ± 875 .04 b, c  Total Crystalloids3 3300 ± 1400 3700 ± 1100 5500 ± 2000 < .001 b, c  Total Colloids3 404 ± 613 474 ± 435 687 ± 414 < .001 b, c  pRBC 23.5 ± 74 205.3 ± 324.7 717 ± 538 < .001 b, c  Fresh Frozen Plasma 0 14.7 ± 13.3 143.4 ± 336.3 < .001 b, c  Cell Saver blood 107 ± 131 285 ± 177 822 ± 450 < .001 a, b, c  NCSB products 3 23.5 ± 73.5 223 ± 350 890 ± 864 < .001 b, c Postoperative outcomes  Delayed extubation (N, %) 1, 2.4% 4, 5.9% 43, 31.6% < .001 N/A  No. of days in ICU 0.6 ± 1.7 1 ± 1.4 2.1 ± 3.0 < .001 b, c  LOS 6.1 ± 2.1 6.4 ± 2.7 7.6 ± 3 .01 b, c  In hospital complications (%) 7, 16.7% 18, 27.6% 51, 37.5% .02 N/A  Major complications4 (%) 2, 4.8% 7, 10.3% 22, 16.2% .11 N/A 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood, LOS- hospital length of stay. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin. NCSB = pRBC + FFP + platelets + cryoprecipitate. 4Early complications categorized as major and minor as recommended.2 5P value in bold represents significance (One way ANOVA). 6a- significance between groups I and II, b- significance between groups II and III, c- significance between groups I and III. View Large Propensity Score Matched Analysis of Volume and Type of Intraoperative Fluids Administered in Patients in IMEX and DEX Groups The weights calculated for the propensity scores for IMEX group ranged from 0.163 to 19.83 with a SD of 2.68. The distribution is as follows: 0.163 (n = 26), 0.176 (n = 25), 0.208 (n = 41), 0.254 (n = 19), 0.416 (n = 9), 0.508 (n = 8), 0.654 (n = 23), 0.763 (n = 15), 0.915 (n = 5), 1.144 (n = 6), 1.526 (n = 9), n = 2 for 2.28, 5.49, 11.44, 19.83, and n = 1 for 1.30, 1.68, 3.81, 4.994, 10.07, and 16.93. PSM analysis of DEX and IMEX demonstrated that, DEX had increased volume of PRBC transfused (939 vs 744 ml, P = .009), greater NCSB infused (1289 vs 937 ml, P = .003), and greater crystalloid: colloid ratios (8.5 ± 6.4 vs 6.8 ± 4.0, P = .03) than IMEX, respectively (Table 3). Total volume of crystalloids, colloids and total fluids infused for IMEX and DEX were similar (P > .05). Table 3. Propensity Score Matched Analysis of Patient Demographics, Surgical Factors and Intraoperative Fluids Among Patients With Immediate vs Delayed Extubation Following Multilevel Thoracolumbar Fusion Procedures1 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin, NCSB = pRBC + FFP + platelets + cryoprecipitate, Total intraoperative fluids = crystalloids + colloids + NCSB products + cell saver blood. 4P value in bold represents significance. 5Crystalloid: colloid ratio was calculated for 188 patients only as 58 patients did not receive colloids and were excluded for this analysis. View Large Table 3. Propensity Score Matched Analysis of Patient Demographics, Surgical Factors and Intraoperative Fluids Among Patients With Immediate vs Delayed Extubation Following Multilevel Thoracolumbar Fusion Procedures1 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 Parameters Immediate extubation (IMEX, n = 198) Delayed extubation (DEX, n = 48) P value4 Cohen's d Demographic  Age (yr) 64.6 ± 11.6 62.6 ± 13.8 .30 0.156  Basal Metabolic Index 27.8 ± 5 27.8 ± 5.6 .93 0  Charlson co-morbidity index 1.4 ± 1.5 1.2 ± 1.4 .25 0.137  ASA grade 2.6 ± 0.6 2.4 ± 0.5 .38 0.362  Malampatti score 1.9 ± 0.6 1.8 ± 0.8 .50 0.14 Surgical  Estimated blood loss (L) 3.12 ± 1.13 3.56 ± 1.84 .19 -0.288  Operative time (min) 431 ± 120 433 ± 133 .93 -0.015  No. of fusion levels 10.7 ± 3.7 10.4 ± 4.1 .62 0.07  3-Column osteotomy (n, %) 87, 45.8% 18, 37.5% .33 NA  Interbody fusion (%) 134, 70.5% 32, 66.7% .60 NA  Surgical invasiveness index2 24.3 ± 7.5 23.8 ± 8.0 .67 0.06 Intra-operative fluids infused (ml)  Ringer lactate (RL) 4980 ± 1950 5280 ± 2500 .37 -0.13  Normal saline (NS) 900 ± 1430 700 ± 800 .52 0.172  Total crystalloids3 5800 ± 1400 6100 ± 2520 .80 -0.147  Total colloids3 856 ± 473 811 ± 322 .53 0.111  pRBC 744 ± 391 939 ± 664 .009 -0.357  Fresh frozen Plasma (FFP) 160 ± 203 293 ± 499 .05 -0.34  Platelets 32.3 ± 102 53.4 ± 197 .30 -0.134  Cell saver 869 ± 410 1002 ± 558 .06 -0.271  NCSB products3 937 ± 552 1289 ± 1193 .003 0.378  Total intraoperative fluids3 8500 ± 2100 9100 ± 3700 .14 -0.199  Crystalloid: Colloid ratio5 (n = 188) 6.8 ± 4.0 8.5 ± 6.4 .03 -0.318 1ASA- American association of Anesthesiologist grade, pRBC- packed red blood cells, NCSB- non-cell saver blood. 2Surgical invasive index calculated according to criteria given by Mirza et al.22 3Total crystalloids = RL + NS, Total colloids = hydroxylethyl starch + albumin, NCSB = pRBC + FFP + platelets + cryoprecipitate, Total intraoperative fluids = crystalloids + colloids + NCSB products + cell saver blood. 4P value in bold represents significance. 5Crystalloid: colloid ratio was calculated for 188 patients only as 58 patients did not receive colloids and were excluded for this analysis. View Large Early Postoperative Complications in IMEX and DEX Groups A total of 69 complications occurred in 246 patients with an overall complication rate of 28%. Fifty-eight patients (23%) had minimum 1 complication and 31 patients (12.3%) had minimum 1 major complication. The mean ICU stay was 2.4 d (range, 0-23) and the mean hospital length of stay was 7.8 days (range, 3-24) for the entire cohort. DEX group had longer ICU (4.0 vs 1.0 d, P < .001) and longer hospital stay (8.9 vs 6.9 d, P = .006) than IMEX (Table 4). DEX had greater cardiac complications (12.5% vs 4%, P = .03), pulmonary complications (18% vs 5%, P = .04), surgical site infections (8.3% vs 1.5%, P = .02) and greater total complication rates than IMEX (50 vs 17.1%, P < .001), respectively. One death occurred in the DEX group due to postoperative pulmonary edema. Table 4. Comparison of Early Postoperative Events and Complications Among Patients With Immediate vs Delayed Extubation Groups Following Complex Thoracolumbar Surgical Procedures Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 1P values in bold represent significance. 2Major complications categorized according to criteria given by Glassman et al.2 3Cardiac complications include congestive heart failure, myocardial infarction, and cardiac arrhythmia. 4Pulmonary complications include airway edema, pulmonary edema, pneumonia, pleural effusion, and ARDS. 5Neurological complications include delirium, severe headache, motor, or sensory deficit. 6Include pressure sores, deep venous thrombosis, and urinary retention requiring catheterization and atelectasis. View Large Table 4. Comparison of Early Postoperative Events and Complications Among Patients With Immediate vs Delayed Extubation Groups Following Complex Thoracolumbar Surgical Procedures Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 Immediate extubations (n = 198) Delayed extubations (n = 48) P value1 Early postoperative outcomes  Length of stay in ICU (d) 1 ± 1.7 4 ± 3.7 < .001  Length of stay in hospital (d) 6.5 ± 2.3 8.9 ± 3.9 .006 Early postoperative complications (%)  All complications 34 (17.1) 24 (50) < .001  Major complications2 16 (8) 15 (31) < .001  Cardiac Complications3 8 (4) 6 (12.5) .03  Pulmonary complications4 10 (5) 9 (18) .04  Neurological complications5 2 (1.01) 2 (4.1) .17  Complications due to immobility6 12 (6) 6 (12.5) .13  Surgical site infection 3 (1.5) 4 (8.3) .02  Death 0 (0) 1 (2.1) .19 1P values in bold represent significance. 2Major complications categorized according to criteria given by Glassman et al.2 3Cardiac complications include congestive heart failure, myocardial infarction, and cardiac arrhythmia. 4Pulmonary complications include airway edema, pulmonary edema, pneumonia, pleural effusion, and ARDS. 5Neurological complications include delirium, severe headache, motor, or sensory deficit. 6Include pressure sores, deep venous thrombosis, and urinary retention requiring catheterization and atelectasis. View Large Analysis of Fluid Proportions and Crystalloid: Colloid Ratios Infused with Increasing EBL in IMEX and DEX Groups Analysis of blood products administered demonstrated an increase in the volume of NCSB products infused with increasing EBL for both IMEX (R = 0.47, P < .001) and DEX (R = 0.35, P = .01). However, with increasing EBL and with increasing NCSB products infused, IMEX had a significant decrease in the proportion of crystalloids administered (R = –0.5, P < .001). Conversely, with increasing EBL and increasing NCSB transfusion, DEX did not demonstrate a significant reduction in the proportion of crystalloids infused (R = –0.27, P = .09, Figure 1). Figure 1. View largeDownload slide Graph showing changes in fluid proportions with increasing EBL. It can be seen that with increasing EBL, the NCSB proportion increases linearly in both IMEX and DEX groups. However, this is accompanied by a significant reduction in the crystalloid proportion in the IMEX group, whereas, the crystalloid proportion relatively remains unchanged in the DEX group. Figure 1. View largeDownload slide Graph showing changes in fluid proportions with increasing EBL. It can be seen that with increasing EBL, the NCSB proportion increases linearly in both IMEX and DEX groups. However, this is accompanied by a significant reduction in the crystalloid proportion in the IMEX group, whereas, the crystalloid proportion relatively remains unchanged in the DEX group. Analysis of crystalloid: colloid administered according to EBL revealed that, in the IMEX group, the ratios of crystalloid: colloid infused decreased with an increase in EBL (R = –0.42, P = .04), whereas, the DEX group demonstrated an increased crystalloid: colloid ratio with an increase in EBL in the DEX group (R = 0.47, P < .001, Figure 2). Figure 2. View largeDownload slide Graph showing trends in crystalloid: colloid ratio infused with increasing estimated blood loss in immediate (IMEX) and delayed (DEX) extubation groups: it can be seen that with increasing blood loss, the crystalloid: colloid infusion ratio increases linearly in the IMEX group (R = 0.42, P = .04) whereas, it decreases in the DEX group (R = –0.47, P < .001). Figure 2. View largeDownload slide Graph showing trends in crystalloid: colloid ratio infused with increasing estimated blood loss in immediate (IMEX) and delayed (DEX) extubation groups: it can be seen that with increasing blood loss, the crystalloid: colloid infusion ratio increases linearly in the IMEX group (R = 0.42, P = .04) whereas, it decreases in the DEX group (R = –0.47, P < .001). Out of 168 patients who received a crystalloid: colloid ratio > 3:1, 44 patients underwent delayed extubation (26%), whereas, none of the 20 patients who received a crystalloid: colloid infusion ratio ≤ 3:1 had delayed extubation (P = .009). DISCUSSION We present a retrospective study on the impact of intraoperative fluids on immediate postoperative extubation status for patients undergoing multilevel thoracic and/or lumbar spine procedures. Not surprisingly, we found that that with increasing complexity of the surgical procedure and increasing blood loss, patients received larger volume of intraoperative fluids, and had increased rates of delayed extubation, greater in-hospital complications and prolonged ICU and hospital stays. However, after controlling for patient demographics, comorbidities, and invasiveness of surgical procedures via PSM analysis, our results indicated that increased volume of NCSB products administered and increased crystalloid: colloid ratios infused are associated with delayed extubation. We also found that, with increasing EBL and increasing NSCB product transfusion, patients that did not have a proportionate decrease in the volume of crystalloids administered were at risk for delayed extubation. Very few studies have evaluated the impact of intraoperative fluid resuscitation on postoperative extubation status and early outcomes following spine procedures.16-19 Li e al18 found that the factors associated with delayed extubation following thoracic and lumbar spine surgeries included operative time, EBL, volume of intraoperative crystalloids and blood products. Similarly, Anastasian et al16 reported that in addition to the above parameters, ASA grade, extent of surgery, and the surgical end time were associated with decision to delay extubation following multilevel spine surgeries. However, these studies are subjected to selection and confounding bias due to the effect of multiple known and unknown demographic and surgical factors on extubation status. We performed PSM analysis to improve patient selection methods and reduce confounding covariates for patients that had immediate or delayed extubation. Increased duration of soft tissue trauma with prolonged surgeries can initiate a cascade of systemic inflammatory response thereby altering the vascular hemodynamics and coagulation profile leading to increased vascular permeability.6 Optimal fluid administration during such events is crucial as excess fluids administered can lead to hemodilution, acidosis, hypothermia, third spacing, abdominal compartment syndrome, respiratory distress syndrome, and multiorgan failure.27-29 This is especially true with crystalloid infusion since, crystalloids are low molecular weight salt solutions as compared to some of the high molecular weight complex colloid solutions. Also, the negatively charged endothelial glycocalyx acts as a strong resistance for permeation of colloids.30 With increasing blood loss; patients tend to receive an increased volume of blood products in order to maintain the oxygen carrying capacity. Since most of the blood products infused remain intravascular, there is a reciprocal reduction in the need for other types of fluids, especially crystalloids to maintain the effective intravascular fluid volume and blood pressure. This explains our findings that with increasing EBL, as patients tend to receive increased proportion of blood products, prompt extubation was possible when patients received a proportionate reduction in the infusion of crystalloids. The ratio of crystalloids: colloids administered during elective noncardiac surgeries have ranged from 0.89 to 4.74, with a trend of persistent reduction over the years.31 Previous studies have shown that 25% of crystalloids infused remain intravascular, whereas, this proportion increases to 75% for colloids.25,26 Therefore, theoretically, the volume of crystalloids required to maintain the same target of intravascular volume would be 3 times that of colloids. This was the basis of our analysis comparing patients who received a crystalloid: colloid ratio > 3:1 with those who received crystalloid: colloid ratios ≤ 3:1. Accordingly, our results indicate patients infused with crystalloid: colloid infusion ratio > 3:1 had a greater occurrence of delayed extubation than patients receiving crystalloid: colloid ratio ≤ 3:1. In our cohort, 58 patients received only crystalloids and were eliminated for the crystalloid: colloid analysis, which might have potential bias in the results. Unfortunately, due to a nonstandard protocol on fluid resuscitation strategies, different anesthesiologist at our institution use different fluid resuscitative measures intraoperatively and there were patients in whom, colloids were not used. Out of these, 54 patients (93%) had immediate extubation. The possible explanation for this observation is that in this group of patients the mean EBL (1.27L), operative time (320 min), cell saver use (314.5ml), and the SII (18.6) were considerably lower than that of the entire cohort of IMEX patients (Table 3), respectively. Previous studies have shown that the effectiveness of crystalloids or colloids in maintaining the intravascular blood volume depends on the existing degree of hypovolemia.32 With relatively mild volume depletion, crystalloids and colloids have almost equal efficacy in maintaining the intraoperative fluid volume. However, with profound hypovolemia, colloids are 4 times more efficacious in maintaining the fluid volume as compared to crystalloids.32,33 In our study, we found that, with increasing EBL, there was a progressive reduction in the crystalloid: colloid ratios infused in patients who underwent prompt extubation. Conversely, patients in the DEX group received increasing ratios of crystalloid: colloid as blood loss increased. These findings suggest that physicians should have a low threshold for using colloids, rather than high volumes of crystalloid, to maintain intravascular volume in the event of large blood loss associated with multilevel spine fusion surgery whenever feasible. The early postoperative complication rate of 28% reported in our study is lower than that described previously for complex spine surgeries, as previously reported rates range from 48.5%-77%.3,34,35 This may be due to the retrospective nature, lack of objective assessment in reporting specific adverse events and focus on major medical complications in our study. In a recent study, Soroceanu et al4 reported an early perioperative medical complication rate of 26.8% in 448 patients undergoing surgery for adult spinal deformities, which is similar to our study. Importantly, we found that patients who underwent delayed extubation had higher cardiac and pulmonary complications and higher surgical site infections than patients receiving immediate extubation. The association between delayed extubation and postoperative complications is multifactorial and has been previously described, including prolonged stasis and poor mobility, prolonged ICU stay, risk for postextubation aspiration pneumonia, venous air embolism, and cardiac arrest. 9,36-39 Although our study is retrospective, we have reported the results of a PSM analyses in an attempt to reduce the effects of confounding variables within our cohort, partially mimicking the effects of randomization. The incorporation of a validated SII has allowed us to compare and control for the surgical elements as a single objective variable and thereby clearly associate the early postoperative outcomes to intraoperative fluid management strategies. However, our study is not without limitations. Limitations Being a single center study, the anesthetic protocol followed for our patients may not represent universal standards. The decision of fluid resuscitation was based on individual anesthesiologist's preference based on the ongoing hemodynamic status of the patient. Similarly, the decision to extubate the patient was based on the patient's co-morbidities, ASA grade, acid-base status, O2 saturation, hemodynamic stability, duration of the procedure, blood loss, and anticipated airway edema and might have been nonstandard. Also, several other parameters like body temperature, acid-base status, mean arterial pressure, anesthetic handoffs, and case end time have not been incorporated, which may have direct implications. Similarly, we did not perform analysis between administration of colloids and postoperative coagulation parameters and renal function tests to determine the effect of colloids. Nonetheless, our results provide data to support the effects of intraoperative fluid management on perioperative outcomes following complex spine surgical procedures. Future research using randomized controlled trials will facilitate formulating guidelines to incorporate fluid management strategies in protocols for managing patients with complex pathologies such as those previously described.40-42 CONCLUSION Our results indicate that increased volume of NCSB products administered and high crystalloid: colloid ratio infused intraoperatively is independently associated with delayed extubation following multilevel spine surgeries. With increasing blood loss, immediate postoperative extubation is facilitated when the proportion of crystalloid fluids administered is proportionately reduced with respect to the total fluids infused. Additionally, 27% of patients who received crystalloid: colloid infusion ratio > 3:1 underwent delayed extubation, whereas no patient underwent delayed extubation when the crystalloid: colloid infusion ratio was ≤ 3:1. Patients with delayed extubation had increased cardiac and pulmonary complications, increased surgical site infections and prolonged ICU and hospital length of stay. Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. REFERENCES 1. Martin BI , Turner JA , Mirza SK , Lee MJ , Comstock BA , Deyo RA . Trends in health care expenditures, utilization, and health status among US adults with spine problems, 1997-2006 . Spine . 2009 ; 34 ( 19 ): 2077 – 2084 . Google Scholar CrossRef Search ADS PubMed 2. Glassman SD , Hamill CL , Bridwell KH , Schwab FJ , Dimar JR , Lowe TG . The impact of perioperative complications on clinical outcome in adult deformity surgery . 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Roger C , Muller L , Deras P et al. Does the type of fluid affect rapidity of shock reversal in an anaesthetized-piglet model of near-fatal controlled haemorrhage? A randomized study . Br J Anaesth. 2014 ; 112 ( 6 ): 1015 – 1023 . Google Scholar CrossRef Search ADS PubMed 33. Zornow MH , Prough DS . Fluid management in patients with traumatic brain injury . New Horiz. 1995 ; 3 ( 3 ): 488 – 498 . Google Scholar PubMed 34. Karstensen S , Bari T , Gehrchen M , Street J , Dahl B . Morbidity and mortality of complex spine surgery: a prospective cohort study in 679 patients validating the Spine AdVerse Event Severity (SAVES) system in a European population . Spine J . 2016 ; 16 ( 2 ): 146 – 153 . Google Scholar CrossRef Search ADS PubMed 35. Klineberg EO , Passias PG , Jalai CM et al. Predicting extended length of hospital stay in an adult spinal deformity surgical population . Spine . 2015 ; 41 ( 13 ): E798 – 805 (Dec 14) doi:10.1097/BRS.0000000000001391 Google Scholar CrossRef Search ADS 36. De Larminat V , Montravers P , Dureuil B , Desmonts JM . Alteration in swallowing reflex after extubation in intensive care unit patients . Crit Care Med. 1995 ; 23 ( 3 ): 486 – 490 . Google Scholar CrossRef Search ADS PubMed 37. Kim MJ , Park YH , Park YS , Song YH . Associations between prolonged intubation and developing post-extubation dysphagia and aspiration pneumonia in non-neurologic critically ill patients . Ann Rehabil Med . 2015 ; 39 ( 5 ): 763 – 771 . Google Scholar CrossRef Search ADS PubMed 38. Brown J , Rogers J , Soar J . Cardiac arrest during surgery and ventilation in the prone position: A case report and systematic review . Resuscitation . 2001 ; 50 ( 2 ): 233 – 238 . Google Scholar CrossRef Search ADS PubMed 39. Albin MS , Ritter RR , Pruett CE , Kalff K . Venous air embolism during lumbar laminectomy in the prone position . Anesth Analg . 1991 ; 73 ( 3 ): 346 – 349 . Google Scholar CrossRef Search ADS PubMed 40. Hart RA , Dupaix JP , Rusa R , Kane MS , Volpi JD . Reduction of airway complications with fluid management protocol in patients undergoing cervical decompression and fusion across the cervicothoracic junction . Spine . 2013 ; 38 ( 18 ): E1135 – E1140 . Google Scholar CrossRef Search ADS PubMed 41. Sethi RK , Pong RP , Leveque JC , Dean TC , Olivar SJ , Rupp SM . The Seattle spine team approach to adult deformity surgery: a systems-based approach to perioperative care and subsequent reduction in perioperative complication rates . Spine Deform . 2014 ; 2 ( 2 ): 95 – 103 . Google Scholar CrossRef Search ADS PubMed 42. Halpin RJ , Sugrue PA , Gould RW et al. Standardizing care for high-risk patients in spine surgery . Spine . 2010 ; 35 ( 25 ): 2232 – 2238 . Google Scholar CrossRef Search ADS PubMed COMMENTS In this study, the authors examine the impact of differing strategies for intraoperative fluid resuscitation of patients undergoing multi-level thoracic and lumbar spine operations. They found that patients receiving high volumes of crystalloids were at increased risk for delayed extubation, and that in patients who received a crystalloid to colloid infusion ratio of ≤ 3, all patients were able to be extubated without delay. Patients undergoing multi-level spine operations are at risk for delayed extubation due to the often prolonged operative times and high fluid volume shifts.1 Previous studies have found a variety of risk factors for delayed extubation including blood transfusion, blood loss, and baseline anesthetic risk.1,2Given the severity of complications that may be associated with prolonged intubation,3,4 such information has value to both neurosurgeons and the anesthesiologists who participate in the care of these patients. The present article is unique in its use of propensity matching in order to control for various possible confounders, and their findings support previous studies suggesting that large volume fluid shifts (especially when aggressive resuscitation is performed using crystalloids) can result in a delay in extubation.3,4 This study is not without limitations, however. The authors point out that resuscitation and extubation decisions, while guided by objective criteria such as oxygen saturation and blood loss, were ultimately the discretion of the anesthesiologist – a factor that was not controlled for and could be a significant source of bias. Before the data from this study can be used to inform care decisions, the findings must be validated. Ideally, this would be done in a prospective manner, with an established, uniform set of criteria for both fluid administration and extubation. Regardless, this article again highlights the importance of appropriate intraoperative anesthesia and fluid management to minimize the risks to patients undergoing complex spine operations. Jian Guan Joel D. MacDonald Salt Lake City, Utah 1. Anastasian ZH Gaudet JG Levitt LC , et al . Factors that correlate with the decision to delay extubation after multilevel prone spine surgery . J Neurosurg Anesthesiol . 2014 ; 26 : 167 – 171 . Google Scholar CrossRef Search ADS PubMed 2. Li F Gorji R Tallarico R Dodds C Modes K Mangat S Yang ZJ . Risk factors for delayed extubation in thoracic and lumbar spine surgery: a retrospective analysis of 135 patients . J Anesth . 2014 ; 28 ( 2 ): 161 – 166 . Google Scholar CrossRef Search ADS PubMed 3. Fagon JY Chastre J Domart Y Trouillet JL Pierre J Darne C Gibert C . Nosocomial pneumonia in patients receiving continuous mechanical ventilation. Prospective analysis of 52 episodes with use of a protected specimen brush and quantitative culture techniques . Am Rev Respir Dis . 1989 ; 139 ( 4 ): 877 – 884 . Google Scholar CrossRef Search ADS PubMed 4. Liu CC Livingstone D Dixon E Dort JC . Early versus late tracheostomy: a systematic review and meta-analysis . Otolaryngol Head Neck Surg . 2015 ; 152 ( 2 ): 219 – 27 . Google Scholar CrossRef Search ADS PubMed The authors provide an interesting retrospective analysis of intraoperative fluid administration and its impact on extubation. Despite the limitations of the study design, the findings agree with generally held observational beliefs that increasing surgical time, blood loss, and crystalloid administration are associated with prolonged intubation. In this cohort, a total of 246 patients were included. The authors found that increased administration of crystalloid to colloid ratio is independently associated with delayed extubation. They also suggest that with increasing EBL, a reduction of crystalloids may allow for early extubation. Carlos David Burlington, Massachusetts The authors present a single-institution analysis to assess the impact of different intraoperative fluid administration strategies on postoperative extubation following elective multi-level thoracic and lumbar spinal fusion. Following a propensity score matching for a number of baseline characteristics, the authors found that patients receiving a delayed extubation had a higher crystalloid to colloid administration ratio and higher use of non-cell saver blood products. Furthermore, upon secondary analysis, they found that delayed extubation was associated with a higher rate of postoperative complications. The authors are to be commended for a rigorous analysis as these are important findings with potential ramifications for spinal neuroanesthesia practice. Propensity score matching helped address the influence of several important confounding covariates, but propensity score matching adds its own bias by removing subjects from the analysis. The crystalloid to colloid ratio findings are likely a result of this propensity score bias. The differences between the immediate and delayed extubation groups in mean crystalloid was only 5800 ml versus 6100 ml and in mean colloid only 856 ml versus 811 ml. Is the reader to conclude that an extra 45 ml of colloid if not delivered with 300 ml of crystalloid will result in significantly worse outcomes and complications? Most likely, the crystalloid colloid ratio would not have been significant on multi-variable regression analysis, making this part of the result a potential example of statistical bias. The study results that would continue to hold significance are that blood transfusions are significantly associated with delayed extubation and longer length of stay. Hopefully, the study team will continue to assess the important findings of their analysis in larger cohorts. Mohamad Bydon Rochester, Minnesota Copyright © 2018 by the Congress of Neurological Surgeons This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Journal

NeurosurgeryOxford University Press

Published: May 30, 2018

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