Backgrounds: Arytenoid dislocation (AD) is a rare but severe complication after general anesthesia with endotracheal intubation. We conducted a case-control study at Peking Union Medical College Hospital to identify risk factors associated with AD, including the use of an intubation stylet. Methods: Patients who experienced AD were matched 1:3 with controls based on gender, age and type of surgery. Multiple conditional logistic regression was performed to determine associations between potential risk factors and AD. Results: Twenty-six AD cases were retrospectively identified from 2004 through 2016. On average, arytenoid dislocation occurred in 2 cases per year, with an incidence of 0.904/100,000 (approximately 0.01%). The 26 patients who experienced AD and 78 matched control patients were enrolled in this study. All enrolled patients underwent endotracheal intubation, and a stylet was used for intubation for 38.5% (10/26) of the AD patients and 64.1% (50/78) of the controls (OR = 0.23, 0.07–0.74). A higher incidence of AD was significantly associated with longer duration of operation (OR = 1.74, 1.23–2.47). Conclusions: The use of an intubation stylet for endotracheal intubation appears to protect against AD. Prolonged operation time increases the risk of AD. These factors should be considered when assessing the risks of AD associated with endotracheal intubation and in efforts to avoid this complication. Keywords: Arytenoid dislocation, Intubation stylet, Duration of operation, Case-control study, Postoperative complication Background Methods Arytenoid dislocation (AD) is a rare postoperative This investigation was a retrospective hospital-based, complication after general anesthesia with tracheal in- case-control study approved by the Peking Union Med- tubation . The incidence of AD after general ical College (PUMC) Hospital Institutional Review anesthesia has been reported to be approximately 0. Board. The study protocol was designated S-K260 and 01–0.1% . The cause of AD may be inadvertent was approved on May 11th, 2017. All the data were trauma to the cricoarytenoid joint from the insertion collected from the adverse-event system in Department of airway tools into the larynx [3–5]. To our know- of Anesthesiology. No written informed consent was ob- ledge, no systematic investigations of AD associated tained from the participants. A verbal consent to partici- with tracheal intubation have been reported. Here, we pation in this study of each participant was obtained report a hospital-based, case-control study to identify through a phone call during follow-up, as all the partici- risk factors for surgery-associated AD. pants had been discharged when we collected the data. Patients * Correspondence: email@example.com; firstname.lastname@example.org From January 2004 to December 2016, 26 cases involv- Department of Anesthesiology, Peking Union Medical College Hospital, ing postoperative AD were reported in the adverse-event Chinese Academy of Medical Sciences and Peking Union Medical College, system. Patients were matched 1:3 (case:control without Beijing, China Full list of author information is available at the end of the article AD) based on gender, age and type of surgery. We also © The Author(s). 2018 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Wu et al. BMC Anesthesiology (2018) 18:59 Page 2 of 5 recorded the following information for each patient: to 2016, with an average of 22,136 such cases per body mass index (BMI), surgical history, pre-existing year (Table 1). Twenty-six cases involving AD, an laryngeal disease, comorbidities, smoking and alcohol average of 2 such cases per year, were recorded; thus, history, American Society of Anesthesiologists physical the incidence of this complication was approximately status classification, number of intubation attempts, 0.01% (0.904/100,000). Cormack Lehane grading during intubation, intubating Table 2 lists basic information for the patients who tools, size of the endotracheal tube, duration of oper- experienced postoperative AD. These 26 patients ation, postoperative admission to the intensive care unit, included 14 males. Their ages ranged from 23 to 83 whether a stylet was used to assist with intubation, and (54.0 ± 17.376) years. With respect to American Society of preoperative baseline laboratory data. Anesthesiologists physical status classification, 8 patients, 15 patients, 2 patients, and 1 patient were categorized as Diagnosis of arytenoid dislocation class I, II, III, and IV, respectively. The types of surgery All the patients with AD appear some similar symptoms performed included various extensive procedures. In within one week after the operations, such as, hoarseness, PUMC hospital, Macintosh direct laryngoscope is the pri- choking when drinking water, and cough. Then electronic marily routine choice for intubation, and the endotracheal fibro-laryngoscopy would be performed by attending tube size is commonly ID 7.5 for male patients and ID 7.0 otolaryngologists to make the final diagnostic reports. for female patients. All AD patients underwent tracheal intubation, and among them only one patient received 3 Statistical analysis attempts of intubation with Shikani optical stylet. Three Categorical variables were expressed as frequencies and AD patients received a double-lumen bronchial tubes, the percentages, which were compared using chi-squared rest 23 AD patients received single-lumen endotracheal tests. Continuous variables were summarized as means tubes, with none of them received a laryngeal mask air- ± SD and compared using Student’s unpaired t-test. We way. AD occurred on the left side in 15 patients and on use Bonferroni correction on the top of simple multiple the right side in 11 patients. No patients in the both group t-tests to adjust the statistical significant level. Multiple suffered pre-existing laryngeal disease or arthritis before conditional logistic regression was performed to deter- the operation. All AD patients recovered or improved mine associations between potential risk factors and AD. after reduction procedure. Statistical analyses were conducted using SPSS 19.0 Table 3 presents comparisons between the cases (SPSS Inc., Chicago, IL, USA). and controls for numerous variables. The following differences were statistically significant. Relative to the Results controls, the AD patients had longer durations of A total of 287,767 cases involving surgery under general operation and longer postoperative hospital stays, but anesthesia were recorded at our hospital from 2004 less frequently underwent intubation involving the use Table 1 Incidence of AD at the PUMCH from 2004 through 2016 Year Total Cases of General Anesthesia Total Cases of AD Incidence of AD (per 100,000) 2004 13,160 1 0.760 2005 14,145 1 0.707 2006 14,666 0 0.000 2007 15,054 0 0.000 2008 15,731 0 0.000 2009 19,190 0 0.000 2010 20,941 2 0.955 2011 21,687 5 2.306 2012 24,960 5 2.003 2013 28,525 3 1.052 2014 31,857 3 0.942 2015 33,192 4 1.205 2016 34,659 2 0.577 Average Cases/Year 22,136 2 0.904 Total Cases 287,767 26 0.904 Wu et al. BMC Anesthesiology (2018) 18:59 Page 3 of 5 Table 2 Basic Information of Patients with Intraoperative AD Case ID Gender Age ASA Name of Surgery AD side A1 2 50–59 II Combined liver resection L A2 2 40–49 I Exploratory laparotomy, Phemister R A3 2 50–59 I Radical operation for stomach carcinoma R A4 1 70–79 I Bowel resection L A5 1 30–39 III Vaginal stump bleeding in suture technique L A6 2 20–29 IV Exploratory laparotomy L A7 2 20–29 I Intracranial brain electrodes L A8 2 80–89 I Open cholecystectomy R A9 1 60–69 II Anterior approach decompression L A10 1 20–29 II Exploratory laparotomy R A11 1 50–59 I Hepatic lateral lobectomy L A12 1 70–79 II Segmental hepatectomy L A13 2 40–49 I Open thoracic exploration, aortic replacement R A14 1 70–79 II Whipple R A15 1 60–69 III CABG L A16 2 30–39 II Aortic replacement R A17 2 60–69 II Miles L A18 2 30–39 II Aortic replacement R A19 1 70–79 II Total knee arthroplasty L A20 2 60–69 II Anterior approach decompression R A21 1 70–79 II LVATS L A22 2 40–49 I Whipple L A23 2 60–69 II LVATS L A24 2 50–59 II Radical operation for cardia carcinoma R A25 1 60–69 II Retroperitoneal neoplasm resection L A26 2 40–49 II Exploratory laparotomy L of an intubation stylet. The duration of operation was Discussion 4.03 ± 1.67 h for the cases and 2.60 ± 1.52 h for the AD is a complication that is known to occur in all surgi- controls (P < 0.002). The two groups did not significantly cal departments, and factors that may either cause or differ with respect to age; gender; BMI; depth of intub- help to prevent AD should be considered. Our incidence ation; frequency of postoperative admission to the inten- rate of AD (approximately 0.01%) is consistent with rates sive care unit; rates of hypertension, diabetes mellitus, reported by Szigeti et al.  and other researchers . smoking, or alcohol use; or results for several preoperative The primary finding of our study is that the use of an in- laboratory tests, including assessments of serum albumin tubation stylet was a significant protective factor for AD. concentration, alanine aminotransferase, prothrombin Although certain authors have reported possible disad- time, and activated partial thromboplastin time. vantages of stylet use, including an increased incidence Table 4 illustrates results from a multiple logistic regres- of postoperative pharyngeal pain  and an increased sion model used to quantify associations between potential frequency of sore throat  caused by removal of the risk factors and AD. Intubation with a stylet was associated stylet. As a teaching hospital, most intubation attempts with a significantly reduced risk of surgery-associated AD were conducted by residents under 5 years, or even (OR = 0.23, 0.07–0.74, P < 0.01), and longer duration of op- medical interns, unless the intubation is too difficult. So eration was associated with a higher risk of AD (OR = 1.89, intubation with a stylet is strongly encouraged especially 1.31–2.74, P < 0.01). Frequency of postoperative admission for those trainees. The reason might be that stylet could to the intensive care unit, American Society of Anesthesiol- decrease violence of laryngeal scope during exposing ogists class III-IV status, BMI, and serum albumin concen- the glottis. An incidental but noteworthy finding of tration were not significant risk factors. our study is that all of the patients in the case group Wu et al. BMC Anesthesiology (2018) 18:59 Page 4 of 5 Table 3 Comparsion between Case and Control Variables Case (n = 26) Control (n = 78) P value Age (mean ± std) 54 ± 17.37 54 ± 17.37 1.000 Male, N (%) 15 (57.7) 45 (57.7) 1.000 BMI (mean ± std) 23.50 ± 3.69 23.19 ± 3.35 0.6863 Length of Surgery (mean ± std) 4.03 ± 1.66 2.60 ± 1.51 0.0002 Depth of Intubation (mean ± std) 23.00 ± 1.85 22.60 ± 1.77 0.1366 Number of attempts > 1,n (%) 1 (3.85) 3 (3.85) 1.000 Cormack Lehane Grade I, n (%) 18 (69.2) 60 (76.9) 0.438 Postopertive Hospital Days (mean ± std) 27.64 ± 12.16 15.88 ± 9.71 < 0.0001 Past Surgical History, n (%) 8 (30.76) 23 (29.48) 1.000 Hypertension, n (%) 6 (23.07) 25 (32.05) 0.464 Diabetes, n (%) 4 (15.38) 12 (15.38) 1.000 Somking, n (%) 5 (19.23) 23 (29.48) 0.444 Alcohol Drinking, n (%) 5 (19.23) 14 (17.95) 1.000 Postoperative ICU Admit, n (%) 5 (19.23) 10 (12.82) 0.519 Stylet Assisted Intubation, n (%) 10 (38.46) 50 (64.10) 0.038 ASA I-II, n (%) 23 (88.46) 63 (80.76) 0.551 Complete Cell Count RBC (10 /L), mean ± std 4.08 ± 0.739 4.38 ± 0.533 0.0268 WBC (10 /L), mean ± std 7.73 ± 2.98 6.503 ± 2.903 0.0127 Hemoglubin (g/L), mean ± std 123.81 ± 22.53 132.71 ± 19.74 0.0516 Platelet (10 /L), mean ± std 216.60 ± 82.60 221.62 ± 83.34 0.5845 Albumin (g/L), mean ± std 38.96 ± 5.72 40.73 ± 4.97 0.0911 ALT (U/L), mean ± std 75.23 ± 196.22 22.69 ± 31.29 0.2161 PT (s), mean ± std 12.81 ± 3.72 12.15 ± 1.361 0.9263 APTT (s), mean ± std 30.25 ± 11.45 28.46 ± 6.241 0.7073 a: American Society of Anesthesiologists underwent intubation; none of these patients received laryngeal masks. Therefore, the use of a laryngeal mask could be an approach for avoiding the occur- rence of postoperative AD. In addition, we found that theseverityof apatient’s health status (specifically, Table 4 Risk Assessment of Intraopeartive AD being ASA class III-IV) and BMI were not related to the incidence of AD. Variables Unadjusted OR 95% CI P value Another important finding of our study was that dur- Use of Stylet 0.35 0.14–0.87 0.03 ation of operation was significantly longer for the AD Duration of Operation 1.71 1.26–2.33 0.00 patients than for the control patients. Logistic analysis ASA 1.08 0.58–2.00 0.81 showed that no stylet use and length of surgery were in- BMI 1.03 0.90–1.17 0.69 dependent risk factors for AD. Other authors  have Tube Depth 1.10 0.88–1.38 0.39 reported that prolonged duration of anesthesia was a significant risk factor for the occurrence of AD and sug- Variables adjusted OR 95% CI P value gested that pressure exerted by a tracheal tube is a cause Use of Stylet 0.23 0.07–0.74 0.01 of AD . However, it is difficult to separate the effects Duration of Operation 1.89 1.31–2.74 0.00 of stylet use and length of surgery. Another of our obser- ASA 1.05 0.90–1.23 0.51 vations was that hospital stay was significantly longer for BMI 1.01 0.48–2.11 0.99 the patients with AD than for the patients without AD; Tube Depth 1.23 0.94–1.62 0.14 we suspect that this difference is related to complexity a: confidence interval of the surgical procedure but not to stylet use. Wu et al. BMC Anesthesiology (2018) 18:59 Page 5 of 5 We also found that compared with the control group, Funding There’s no funding in this manuscript. the case group had significantly lower preoperative per- ipheral red blood cell counts and significantly higher Authors’ contributions white blood cell counts; however, the blood counts of LW collected the data, conduct statistic analysis and drafted the manuscript. LS directed the design of the study, modify the article. YZ participated in the both groups were within the normal range, and logistic statistical analysis. XZ participated in the quality control of the study. YH analysis showed that neither of these counts was an in- conceived of the study, and participated in its design and coordination. All dependent risk factor for AD. Therefore, the significance authors read and approved the final manuscript. of these hematologic findings with respect to AD is un- Ethics approval and consent to participate clear. Anemia or joint inflammation may lead to instabil- This investigation was a retrospective hospital-based, case-control study ity , but it is not known whether either of these approved by the Peking Union Medical College (PUMC) Hospital Institutional Review Board. All the data were collected from the adverse-event system in phenomena is relevant to the cause of AD. The results Department of Anesthesiology. No written informed consent was obtained of several other common laboratory tests were also not from the participants. A verbal consent to participation in this study of each significantly associated with AD; thus, our study did not participant was obtained through a phone call during follow-up, as all the participants had been discharged when we collected the data. The study identify a preoperative laboratory test that could predict protocol was designated S-K260 and was approved on May 11th, 2017. the occurrence of AD. In our series, no cases of AD were recorded during Consent for publication I declare to consent for publication and there’s no individual identifying data. 2006–2009. We suspect that the reason for this phenomenon is that the Department of Anesthesiology’s Competing interests adverse-event system was improved after 2010, with bet- The authors declare that they have no competing interests. ter follow-up of anesthesiologists’ performance. So there should be some missing AD cases in the cohort, as is a Publisher’sNote Springer Nature remains neutral with regard to jurisdictional claims in major limitation for our research. So we need to improve published maps and institutional affiliations. our adverse event reporting system to achieve more cases in future. Author details Department of Anesthesiology, Peking Union Medical College Hospital, This study has some other limitations. For example, Chinese Academy of Medical Sciences and Peking Union Medical College, this study was a retrospective case-control study and 2 Beijing, China. Central Research Laboratory, Peking Union Medical College may therefore have incorporated selection bias. Age, Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China. gender and surgery department could not be analyzed in this investigation. Secondly, since postoperative AD is a Received: 18 February 2018 Accepted: 11 May 2018 rare complication, our case group contained only 26 patients. Large, multi-center prospective trials may be References needed to conclusively establish whether the use of an 1. Szigeti CL, Baeuerle JJ, Mongan PD. Arytenoid dislocation with lighted stylet intubation stylet protects against AD. intubation: case report and retrospective review. Anesth Analg. 1994;78(1): 185–6. In conclusion, AD is a rare but severe complication 2. 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Rieger A, Hass I, Gross M, Gramm HJ, Eyrich K. Intubation trauma of the We are grateful to Dr. Min Yao for valuable discussion. larynx–a literature review with special reference to arytenoid cartilage dislocation. Anasthesiologie, Intensivmedizin, Notfallmedizin, Availability of data and material Schmerztherapie : AINS. 1996;31(5):281–7. The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.
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Published: May 31, 2018