Capillary and venous lactate measurements with a handheld device compared to venous blood-gas analysis for emergency patients

Capillary and venous lactate measurements with a handheld device compared to venous blood-gas... Background/aim: Early identification of lactate levels may have a large impact on triage classification and assist in identifying critically ill patients. A handheld device provides a rapid and timesaving measurement of lactate levels adapted to work in a prehospital care setting. I.e., the device is small, fast, and easy-to-use. The aim of this study was to evaluate the Accutrend Plus handheld lactate analyzer in comparison to the reference in-hospital method. Methods: Patients triaged as minimum yellow according to the RETTS System (Rapid Emergency Triage and Treatment System) and transported to hospital by ambulance were selected and a written consent to participate was obtained prior to inclusion in the study. Capillary (CAP) and venous (VEN) blood were analyzed with Accutrend Plus (AP). Venous blood samples were analyzed at the local hospital laboratory (GEM premier 4000) within 20 min from sampling. All sampling was conducted by two registered nurses specially trained in prehospital care. Results: 480 lactate measurements were performed in 160 patients. The mean difference between measurements in capillary blood compared with the reference method was 0.7 mmol/L and for venous blood 0.9 mmol/L. The limits of agreement from the Bland-Altman plot was − 0.9 to + 2.5 mmol/L and and − 0.1 to + 1.9 mmol/L, for CAP and VEN compared with GEM. Conclusion: Our results shows low accuracy and low precision with VEN / CAP measurements of lactate compared to reference GEM. Keywords: Handheld lactate analyzer, Lactate, Prehospital emergency care, Point of care (POC) Background The most common triage system used prehospitally In prehospital care, it is important to triage patients cor- and in emergency wards in Sweden, is at present RETTS rectly based on the severity of their injuries/conditions (Rapid Emergency Triage and Treatment System), which [1]. Measurement of lactate levels in addition to stand- is high-sensitive in detecting critical patients [2]. The ard parameters, e.g. vital signs, might improve the as- RETTS system uses vital signs, e.g. respiratory rate, oxy- sessment of severity, choice of level of care and gen saturation, pulse and blood pressure combined with destination for the patient. However, the significance of signs and symptoms of the patient. The system also con- lactate levels cannot be determined accurately until an siders medical history and experiences on development adapted equipment is available in a prehospital of different medical conditions. The vital signs used by environment. the RETTS system (see above) are not sufficient to re- flect anaerobic metabolism and acidosis which is of great interest in the valuation of critical conditions. Lactate * Correspondence: David.stoll@lvn.se levels are often considered to be better resuscitation Deceased endpoints than standard vital signs. Early identifications Ambulance Services, Sundsvall Hospital, Västernorrland County Council, 851 86 Sundsvall, Sweden of lactate levels may have a large impact on triage Full list of author information is available at the end of the article © 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. Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 2 of 5 classification and assist in identifying critically ill pa- tients [3, 4]. An ideal prehospital device would provide a rapid analyze and be adapted to a prehospital setting i.e., carry little weight and be of small size as well as being easy to handle at bedside and have simple hygienic pro- cedures [4]. Previous studies Jansen et al. [5] examined the associ- ation between elevated lactate detected prehospital and mortality rate. Baldari et al. [6] and Pyne et al. [7] inves- tigated the reliability of the AP in young healthy athletes where the results showed a linear relationship to the ref- erence method taken from capillary blood samples. Pat- tharanitima et al. [8] demonstrated a high correlation and good agreement between arterial and capillary lac- tate values, as well as high correlations between arterial and central venous lactate values of 30 sepsis patients with AP in hospital settings. However, we have not found any studies that have examined the reliability of Accutrend Plus (AP) using capillary and venous blood samples in prehospital environment. Arterial lactate analysis is the conventional method used to analyze lactate. However, arterial blood samples require technologies and equipment’s that are not suit- able for prehospital settings. The aim of this study was to test the Accutrend Plus handheld lactate analyzer to evaluate its performance in a prehospital environment in comparison to the reference in-hospital method. Fig. 1 Flowchart Methods A prospective observational study was conducted in the Ambulance Services in Västernorrland County Hospital Ethics Sundsvall, in association with Karolinska Institutet, from The study was approved by the regional committee for April 1st, 2014 to April 1st, 2015. medical and health research ethics at Umeå (Ref. 2014– 14-31 M). Each participant was given a verbal and writ- ten information of the study. All participation was vol- Subjects untarily and a written consent to participate was One hundred sixty patients transported to hospital by obtained prior to inclusion. ambulance were included in the study (Fig. 1). Inclusion criteria were patients older than 18 years of age who, ac- Procedure cording to the triage system Rapid Emergency Triage Data were collected by two specially selected ambulance and Treatment System (RETTS), were triaged red, or- nurses (1st and 4th authors) with more than 10 years’ ange or yellow by two ambulance nurses (1st and 4th experience of blood sampling. Only patients presented authors). Red priority is defined as patient in need of to the ambulance service when the two nurses were on medical assessment immediately, i.e. to see a doctor in- duty could be included. Patients transported to hospital stantly on arrival to the emergency ward. Orange prior- received peripheral venous access in the upper limb be- ity is defined as a patient in need of medical assessment fore leaving the ambulance, according to local medical within 20 min and yellow priority within 120 min [2] guidelines. Capillary and venous blood samples were col- after arrival to the emergency ward. lected simultaneously as venous access within a 5– Patients in palliative treatment, circulatory arrest, 10 min window from arrival. Venous sampling was con- with a history of coagulopathy, or requiring immedi- ducted without a tourniquet. All samplings were done ate medical treatment for life threatening conditions, simultaneously. No saline or drugs were used in the can- and those patients who could not understand or re- nula before samples were taken. Blood was not aspirated ceive information about the study were excluded. and discarded before sampling. The analysis of the AP Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 3 of 5 took approximately 2–3 min. The analysis of the lactate agreement. Two cut-points, 2 and 3.5, were used to de- sample in the hospital’s local laboratory was conducted scribe how the capillary and venous lactate measurement within 20 min after sampling. This measure was used as behave for different severity intervals [5]. Parametric reference (GEM Premier 4000). methods were used as the size of sample permits the as- Measurement of lactate was analyzed as follows: sumption normal distribution. Statistical analyzes were performed using IBM SPSS 23. Graphics was created in Capillary (CAP) - a drop of blood from the fingertip Origin 9.0. analyzed by AP. Venous (VEN) - venous blood collected by back- Results flow from the venous access and analyzed by AP. Four hundred eighty lactate measurements were ana- Venous Intrashop Paired analyzed by hospital - four lyzed from 160 patients. Mean age was 70.1 years, and milliliter venous blood was collected by back-flow 50% were women (Tables 1 and 2). from the pre-existing cannula into a lithium heparin- The analysis with AP measured an ICC level of 0.76 ized standard sample tube. The sample was analyzed (CI: 0.27–0.90) in CAP and 0.79 (CI: 0.00–0.94) in VEN. at the local hospital laboratory by GEM Premier 4000 The mean difference (Bias value) of all measurements in (GEM). GEM sample was used as the reference, and CAP compared with GEM was 0.7 mmol/L. The level of analyzed within 20 min after collection of the sample. agreement indicated that for 95% of the measurements differences would be between − 0.9 to + 2.5 mmol/L. All 160 patients had their lactate measured three times The mean difference (Bias value) of all measurements (CAP, VEN and GEM) giving a total of 480 samples. AP in VEN compared with GEM was 0.9 mmol/L. The level and GEM samples were calibrated regularly according to of agreement indicated that for 95% of the measure- instructions by the manufacturers. ments differences would be between − 0.1 to + 1.9 mmol/L (Fig. 2a and b. Lactate analyzers The AP lactate analyser (Roche, Diagnostic international Discussion Ltd.) is a portable, battery-driven device that weighs ap- We have in our study added data on capillary and ven- proximately 140 g. AP measures whole blood lactate ous sampling with a device that seems practical to use values sampled from capillary blood. The measuring prehospitally. Our study of CAP and VEN sample ana- range is 0.8–22 mM. A drop of blood is applied on a lysis showed generally higher values (mean bias, 0.7 and chemistry strip and analyzed with a reflectance photo- 0.9 and upper level of limits of agreement, 2.4 and metric method. The result is displayed with a turn- 1.9 mmol/L) than the reference method GEM (Fig. 2). around time of 60 s. This agrees with results from Baldari et al. [6] that also GEM Premier 4000 (Instrumentation Laboratory) is a demonstrated higher levels of lactate in healthy athletes compact (20 kg) system used for whole blood analyzes when using handheld analyzers. The Bland-Altman plot and designed for emergency- and central laboratory test- shows high bias in both VEN and CAP, although some- ing. The analyzer measures blood gases of a single whole what higher in VEN. The precision is superior with VEN blood sample with an amperometric and potentiometric than CAP which may be more important than the bias. method. High precision is associated with low risk for underesti- mation, which is, from a clinical point of view, safer. Statistics Table 1 Patients characteristics (n = 160) One hundred sixty patients were estimated to give a suf- ficient sample size to be able to detect an ICC (intraclass Variables\Triage Yellow Orange Red category correlation coefficient) of 0.8 when intraclass- correl- n =65 n =81 n =14 ation in the null hypothesis is 0.7. This is based on an Age F-test and on two observations per individual with a Mean (Range) 70.7 (40–96) 70.2 (20–96) 67.8 (45–83) power of 90% and a significance level of 5% [9]. Gender The agreement of AP compared with the reference Female 42 (65%) 35 (43%) 3 (21%) method was determined using Bland Altman plots. This Accutrend Plus was used to visualize both the accuracy (bias), and preci- sion. The sample size was also in line with recommenda- Capillary ≤3.5 mmol/L 54 (83%) 71 (88%) 8 (57%) tion for Bland-Altman plot [10]. Correlation between AP Venous ≤3.5 mmol/L 60 (92%) 74 (91%) 6 (43%) and the reference method GEM was estimated by intra- Gem Premier 4000 class correlation coefficient (ICC (2.1)), where ICC Venous ≤3.5 mmol/L 63 (97%) 79 (98%) 9 (64%) values greater than 0.8 was interpreted to be in absolute Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 4 of 5 Table 2 Lactate levels measured with Accutrend Plus and Gem Table 3 Mean, standard deviation and bias of Accutrend Plus 4000 (n = 160) and GEM Analyser ≤2 mmol/L > 2 - ≤3.5 mmol/L > 3.5 mmol/L GEM 0 - ≤2 GEM > 2 - ≤3.5 Total Number Number Number Mean SD Bias Mean SD Bias Mean SD Bias Accutrend Plus Accutrend Plus Capillary 68 65 27 Capillary 2.18 0.86 0.77 3.29 0.93 0.47 2.55 1.51 0.72 Venous 48 92 20 Venous 2.27 0.60 0.86 3.70 0.74 0.88 2.71 1.48 0.88 Gem Premier 4000 GEM Venous 128 23 9 Venous 1.41 0.34 – 2.82 0.72 – 1.83 1.37 – Data are presented as mean, standard deviation (SD) and bias for values were GEM is between 0 and 2, 2–3.5 as well as Total. Bias = mean difference The Bland-Altman plot also illustrates if the variation of between AP lactate levels and GEM differences is constant through different values on the x-axis. It seems to be the case for values under 4, but it’s The limits of agreement show an existing bias in both difficult to assess if the same is true for values > 4 as lactate measurements but slightly larger for VEN. The only a few values are > 4 in our study [10]. Moreover, no limit is wider for CAP compared to VEN. The scatter of sign of systematic change in bias in the Bland-Altman the differences is constant in increasing values on the plot. In Table 3 only small changes in mean bias was x-axis, both for CAP and VEN-values. The bias in CAP found when GEM values were 0–2 mmol/L and 2– is lower than in VEN, but for values below 2 mmol/L 3.5 mmol/L (Fig. 2). Our results show a low accuracy and between 2 and 2.5 mmol/L bias is more stable for with CAP, as well as with VEN analyzed with the hand- VEN (Table 3). held AP compared to the reference method GEM. This is in discrepancy to Baldari [6] and Pyne et al. [7] who Limitations investigated the reliability of the AP in young healthy Time between sample and analysis was seconds for the athletes and where the results showed a good linear rela- handheld analyzer. The blood samples were collected tionship with the reference method using capillary blood upon arrival by two nurses (authors 1 and 4) using the samples. Pattharanitima et al. [8] also showed a high cor- same procedure for all patients included. No local injuries relation between arterial and capillary lactate values, as or issues in the limbs where the samples were collected well as high correlation between arterial and central ven- where found for any of the patients included in the study ous lactate values in 30 septic inhospital patients using during the stay at the emergency ward. All samples tested AP. Our results concur with Datta et al. [11] who demon- with GEM were analyzed within 20 min (30 min stipu- strated a poor agreement of capillary lactate analyzes in lated by manufacturer). We consider our bias concerning comparison to peripheral venous lactate measurements. differences in sampling procedures minute. a b Fig. 2 a, b The Bland-Altman plots describes the level of agreement between the CAP/VEN measurements and the reference method. The Y-axis represents the differences between CAP/VEN and GEM. The X axis represents the mean of CAP/VEN and GEM. The dotted lines displays mean of the differences and the 95% limits of agreements Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 5 of 5 As shown in Table 1 the majority (91,2%) of the in- gas analysis for emergency patients, has been read and approved by all named authors and that there are no other persons who satisfied the criteria cluded patients were triaged orange/yellow and only a for authorship. We further confirm that the order of authors listed in the few red patients could be included. This may have se- manuscript has been approved by all of us. The manuscript has not been lected a category of patients with similar lactate levels published, or submitted for publication elsewhere. Unfortunately, one of the authors (author number four) has recently died (2017). and minimized the spread of our measurements. The discrepancy to the results found by Baldari [6] and Pyne Ethics approval and consent to participate et al. [7] who investigated capillary samples in young The study was approved by the regional committee for medical and health research ethics at Umeå (Ref. 2014–14-31 M). Each participant was given a healthy athletes and Pattharanitima et al. [8] who ana- verbal and written information of the study. All participation was voluntarily lyzed capillary samples from septic patients could per- and a written consent to participate was obtained prior to inclusion. haps be explained by the difference in the selection of Competing interests patients. Where our study had a relatively large number The authors declare that they have no competing interests. of patients (n = 160 triaged mainly as orange/yellow pri- ority) with a similar level of lactate the Baldari study [6] Publisher’sNote showed a wider range of lactate levels. The red/orange Springer Nature remains neutral with regard to jurisdictional claims in patients included with possible low blood-pressure may published maps and institutional affiliations. have had peripheral vasoconstriction. This may account Author details for differences between VEN and CAP levels. 1 Ambulance Services, Sundsvall Hospital, Västernorrland County Council, 851 We found that lactate levels measured with CAP, as 86 Sundsvall, Sweden. Research and Development, Sundsvall Hospital, Västernorrland County Council, Sundsvall, Sweden. Karolinska Institutet, well as VEN, were higher than the values measured with Department of Physiology and Pharmacology, Stockholm, Sweden. GEM (Fig. 2). The spread of 2 mmol/L above values an- alyzed by GEM was more frequent for CAP than for Received: 20 December 2017 Accepted: 14 May 2018 VEN. Baldari et al. [6] found that the deviation with the handheld compared to stationary blood-gas analyzers es- References calated with higher lactate values. The measured levels 1. The National Association of Emergency Medical Technicians, NAEMT PHTLS. Prehospital trauma life support. 7th ed. St. Louis: Elsevier Mosby; 2011. of lactate in our study were generally lower than 2. Widgren B, Jourak M. Medical emergency triage and treatment system 6 mmol/L which gives a small spread of the results and (METTS): a new protocol in primary triage and secondary priority decision in may account for our small deviation from reference. Fur- emergency medicine. J Emerg Med. 2011;40:623–8. 3. Goyal M, Pines JM, Drumheller BC, Gaieski DF. Point-of-care testing at ther studies with patients in critical conditions with a triage decreases time to lactate level in septic patients. J Emerg Med. wider spread of lactate levels are needed to be able to 2010;38:578–81. fully evaluate the potential use of CAP samples. 4. Slomovitz BM, Lavery RF, Tortella BJ, Siegel JH, Bachl BL, Ciccone A. Validation of a hand-held lactate device in determination of blood lactate in critically injured patients. Crit Care Med. 1998;26:1523–8. Conclusion 5. Jansen TC, van Bommel J, Mulder PG, Rommes JH, Schieveld SJ, Bakker J. Our results demonstrate low accuracy and relatively low The prognostic value of blood lactate levels relative to that of vital signs in the pre-hospital setting: a pilot study. Crit Care. 2008;12:R160. precision with VEN / CAP measurements of lactate com- 6. Baldari C, Bonavolonta V, Emerenziani GP, Gallotta MC, Silva AJ, Guidetti L. pared to reference GEM. Our results also suggest that VEN Accuracy, reliability, linearity of Accutrend and lactate pro versus EBIO plus are safer than CAP measurements because of its better analyser. Eur J Appl Physiol. 2009;107:105–11. 7. Pyne DB, Boston T, Martin DT, Logan A. Evaluation of the lactate pro blood precision. lactate analyser. Eur J Appl Physiol. 2000;82:112–6. 8. Pattharanitima P, Tongyoo S, Ratanarat R, Wilachone W, Poompichet A, Abbreviations Permpikul C. Correlation of arterial, central venous and capillary lactate AP: Accutrend plus; CAP: Capillary; GEM: GEM premier 4000; VEN: Venous levels in septic shock patients. J Med Assoc Thail. 2011;94(Suppl 1):175–80. 9. Walter SD, Eliasziw M, Donner A. Sample size and optimal designs for Funding reliability studies. Stat Med. 1998;17:101–10. This study was supported by grants from Emil Andersson foundation for 10. Bland JM, Altman DG. Statistical methods for assessing agreement between medical research and comity for patient safety/Research and Development, two methods of clinical measurement. Lancet. 1986;8:307–10. Västernorrland County Council. 11. Datta D, Grahamslaw J, Gray AJ, Graham C. Capillary and venous lactate There has been no significant financial support for this work that could have agreement: a pilot prospective observational study. Emerg Med J. 2017;34: influenced its outcome. 195–7. Availability of data and materials Please contact the corresponding author for data request. Authors’ contributions Lactate measurement prehospitally has a potential to be one of the important tools in the triage of trauma patients and may help to decide the correct destination. This manuscript is a contribution to the clinical experience of one the lactate device available. All authors planned the study, discussed the presentation of data and approved the final draft. DS and SV collected the data. We confirm that the manuscript, Capillary and venous lactate measurements with a handheld device compared to venous blood- http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine Springer Journals

Capillary and venous lactate measurements with a handheld device compared to venous blood-gas analysis for emergency patients

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Medicine & Public Health; Emergency Medicine; Traumatic Surgery
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Abstract

Background/aim: Early identification of lactate levels may have a large impact on triage classification and assist in identifying critically ill patients. A handheld device provides a rapid and timesaving measurement of lactate levels adapted to work in a prehospital care setting. I.e., the device is small, fast, and easy-to-use. The aim of this study was to evaluate the Accutrend Plus handheld lactate analyzer in comparison to the reference in-hospital method. Methods: Patients triaged as minimum yellow according to the RETTS System (Rapid Emergency Triage and Treatment System) and transported to hospital by ambulance were selected and a written consent to participate was obtained prior to inclusion in the study. Capillary (CAP) and venous (VEN) blood were analyzed with Accutrend Plus (AP). Venous blood samples were analyzed at the local hospital laboratory (GEM premier 4000) within 20 min from sampling. All sampling was conducted by two registered nurses specially trained in prehospital care. Results: 480 lactate measurements were performed in 160 patients. The mean difference between measurements in capillary blood compared with the reference method was 0.7 mmol/L and for venous blood 0.9 mmol/L. The limits of agreement from the Bland-Altman plot was − 0.9 to + 2.5 mmol/L and and − 0.1 to + 1.9 mmol/L, for CAP and VEN compared with GEM. Conclusion: Our results shows low accuracy and low precision with VEN / CAP measurements of lactate compared to reference GEM. Keywords: Handheld lactate analyzer, Lactate, Prehospital emergency care, Point of care (POC) Background The most common triage system used prehospitally In prehospital care, it is important to triage patients cor- and in emergency wards in Sweden, is at present RETTS rectly based on the severity of their injuries/conditions (Rapid Emergency Triage and Treatment System), which [1]. Measurement of lactate levels in addition to stand- is high-sensitive in detecting critical patients [2]. The ard parameters, e.g. vital signs, might improve the as- RETTS system uses vital signs, e.g. respiratory rate, oxy- sessment of severity, choice of level of care and gen saturation, pulse and blood pressure combined with destination for the patient. However, the significance of signs and symptoms of the patient. The system also con- lactate levels cannot be determined accurately until an siders medical history and experiences on development adapted equipment is available in a prehospital of different medical conditions. The vital signs used by environment. the RETTS system (see above) are not sufficient to re- flect anaerobic metabolism and acidosis which is of great interest in the valuation of critical conditions. Lactate * Correspondence: David.stoll@lvn.se levels are often considered to be better resuscitation Deceased endpoints than standard vital signs. Early identifications Ambulance Services, Sundsvall Hospital, Västernorrland County Council, 851 86 Sundsvall, Sweden of lactate levels may have a large impact on triage Full list of author information is available at the end of the article © 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. Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 2 of 5 classification and assist in identifying critically ill pa- tients [3, 4]. An ideal prehospital device would provide a rapid analyze and be adapted to a prehospital setting i.e., carry little weight and be of small size as well as being easy to handle at bedside and have simple hygienic pro- cedures [4]. Previous studies Jansen et al. [5] examined the associ- ation between elevated lactate detected prehospital and mortality rate. Baldari et al. [6] and Pyne et al. [7] inves- tigated the reliability of the AP in young healthy athletes where the results showed a linear relationship to the ref- erence method taken from capillary blood samples. Pat- tharanitima et al. [8] demonstrated a high correlation and good agreement between arterial and capillary lac- tate values, as well as high correlations between arterial and central venous lactate values of 30 sepsis patients with AP in hospital settings. However, we have not found any studies that have examined the reliability of Accutrend Plus (AP) using capillary and venous blood samples in prehospital environment. Arterial lactate analysis is the conventional method used to analyze lactate. However, arterial blood samples require technologies and equipment’s that are not suit- able for prehospital settings. The aim of this study was to test the Accutrend Plus handheld lactate analyzer to evaluate its performance in a prehospital environment in comparison to the reference in-hospital method. Fig. 1 Flowchart Methods A prospective observational study was conducted in the Ambulance Services in Västernorrland County Hospital Ethics Sundsvall, in association with Karolinska Institutet, from The study was approved by the regional committee for April 1st, 2014 to April 1st, 2015. medical and health research ethics at Umeå (Ref. 2014– 14-31 M). Each participant was given a verbal and writ- ten information of the study. All participation was vol- Subjects untarily and a written consent to participate was One hundred sixty patients transported to hospital by obtained prior to inclusion. ambulance were included in the study (Fig. 1). Inclusion criteria were patients older than 18 years of age who, ac- Procedure cording to the triage system Rapid Emergency Triage Data were collected by two specially selected ambulance and Treatment System (RETTS), were triaged red, or- nurses (1st and 4th authors) with more than 10 years’ ange or yellow by two ambulance nurses (1st and 4th experience of blood sampling. Only patients presented authors). Red priority is defined as patient in need of to the ambulance service when the two nurses were on medical assessment immediately, i.e. to see a doctor in- duty could be included. Patients transported to hospital stantly on arrival to the emergency ward. Orange prior- received peripheral venous access in the upper limb be- ity is defined as a patient in need of medical assessment fore leaving the ambulance, according to local medical within 20 min and yellow priority within 120 min [2] guidelines. Capillary and venous blood samples were col- after arrival to the emergency ward. lected simultaneously as venous access within a 5– Patients in palliative treatment, circulatory arrest, 10 min window from arrival. Venous sampling was con- with a history of coagulopathy, or requiring immedi- ducted without a tourniquet. All samplings were done ate medical treatment for life threatening conditions, simultaneously. No saline or drugs were used in the can- and those patients who could not understand or re- nula before samples were taken. Blood was not aspirated ceive information about the study were excluded. and discarded before sampling. The analysis of the AP Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 3 of 5 took approximately 2–3 min. The analysis of the lactate agreement. Two cut-points, 2 and 3.5, were used to de- sample in the hospital’s local laboratory was conducted scribe how the capillary and venous lactate measurement within 20 min after sampling. This measure was used as behave for different severity intervals [5]. Parametric reference (GEM Premier 4000). methods were used as the size of sample permits the as- Measurement of lactate was analyzed as follows: sumption normal distribution. Statistical analyzes were performed using IBM SPSS 23. Graphics was created in Capillary (CAP) - a drop of blood from the fingertip Origin 9.0. analyzed by AP. Venous (VEN) - venous blood collected by back- Results flow from the venous access and analyzed by AP. Four hundred eighty lactate measurements were ana- Venous Intrashop Paired analyzed by hospital - four lyzed from 160 patients. Mean age was 70.1 years, and milliliter venous blood was collected by back-flow 50% were women (Tables 1 and 2). from the pre-existing cannula into a lithium heparin- The analysis with AP measured an ICC level of 0.76 ized standard sample tube. The sample was analyzed (CI: 0.27–0.90) in CAP and 0.79 (CI: 0.00–0.94) in VEN. at the local hospital laboratory by GEM Premier 4000 The mean difference (Bias value) of all measurements in (GEM). GEM sample was used as the reference, and CAP compared with GEM was 0.7 mmol/L. The level of analyzed within 20 min after collection of the sample. agreement indicated that for 95% of the measurements differences would be between − 0.9 to + 2.5 mmol/L. All 160 patients had their lactate measured three times The mean difference (Bias value) of all measurements (CAP, VEN and GEM) giving a total of 480 samples. AP in VEN compared with GEM was 0.9 mmol/L. The level and GEM samples were calibrated regularly according to of agreement indicated that for 95% of the measure- instructions by the manufacturers. ments differences would be between − 0.1 to + 1.9 mmol/L (Fig. 2a and b. Lactate analyzers The AP lactate analyser (Roche, Diagnostic international Discussion Ltd.) is a portable, battery-driven device that weighs ap- We have in our study added data on capillary and ven- proximately 140 g. AP measures whole blood lactate ous sampling with a device that seems practical to use values sampled from capillary blood. The measuring prehospitally. Our study of CAP and VEN sample ana- range is 0.8–22 mM. A drop of blood is applied on a lysis showed generally higher values (mean bias, 0.7 and chemistry strip and analyzed with a reflectance photo- 0.9 and upper level of limits of agreement, 2.4 and metric method. The result is displayed with a turn- 1.9 mmol/L) than the reference method GEM (Fig. 2). around time of 60 s. This agrees with results from Baldari et al. [6] that also GEM Premier 4000 (Instrumentation Laboratory) is a demonstrated higher levels of lactate in healthy athletes compact (20 kg) system used for whole blood analyzes when using handheld analyzers. The Bland-Altman plot and designed for emergency- and central laboratory test- shows high bias in both VEN and CAP, although some- ing. The analyzer measures blood gases of a single whole what higher in VEN. The precision is superior with VEN blood sample with an amperometric and potentiometric than CAP which may be more important than the bias. method. High precision is associated with low risk for underesti- mation, which is, from a clinical point of view, safer. Statistics Table 1 Patients characteristics (n = 160) One hundred sixty patients were estimated to give a suf- ficient sample size to be able to detect an ICC (intraclass Variables\Triage Yellow Orange Red category correlation coefficient) of 0.8 when intraclass- correl- n =65 n =81 n =14 ation in the null hypothesis is 0.7. This is based on an Age F-test and on two observations per individual with a Mean (Range) 70.7 (40–96) 70.2 (20–96) 67.8 (45–83) power of 90% and a significance level of 5% [9]. Gender The agreement of AP compared with the reference Female 42 (65%) 35 (43%) 3 (21%) method was determined using Bland Altman plots. This Accutrend Plus was used to visualize both the accuracy (bias), and preci- sion. The sample size was also in line with recommenda- Capillary ≤3.5 mmol/L 54 (83%) 71 (88%) 8 (57%) tion for Bland-Altman plot [10]. Correlation between AP Venous ≤3.5 mmol/L 60 (92%) 74 (91%) 6 (43%) and the reference method GEM was estimated by intra- Gem Premier 4000 class correlation coefficient (ICC (2.1)), where ICC Venous ≤3.5 mmol/L 63 (97%) 79 (98%) 9 (64%) values greater than 0.8 was interpreted to be in absolute Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 4 of 5 Table 2 Lactate levels measured with Accutrend Plus and Gem Table 3 Mean, standard deviation and bias of Accutrend Plus 4000 (n = 160) and GEM Analyser ≤2 mmol/L > 2 - ≤3.5 mmol/L > 3.5 mmol/L GEM 0 - ≤2 GEM > 2 - ≤3.5 Total Number Number Number Mean SD Bias Mean SD Bias Mean SD Bias Accutrend Plus Accutrend Plus Capillary 68 65 27 Capillary 2.18 0.86 0.77 3.29 0.93 0.47 2.55 1.51 0.72 Venous 48 92 20 Venous 2.27 0.60 0.86 3.70 0.74 0.88 2.71 1.48 0.88 Gem Premier 4000 GEM Venous 128 23 9 Venous 1.41 0.34 – 2.82 0.72 – 1.83 1.37 – Data are presented as mean, standard deviation (SD) and bias for values were GEM is between 0 and 2, 2–3.5 as well as Total. Bias = mean difference The Bland-Altman plot also illustrates if the variation of between AP lactate levels and GEM differences is constant through different values on the x-axis. It seems to be the case for values under 4, but it’s The limits of agreement show an existing bias in both difficult to assess if the same is true for values > 4 as lactate measurements but slightly larger for VEN. The only a few values are > 4 in our study [10]. Moreover, no limit is wider for CAP compared to VEN. The scatter of sign of systematic change in bias in the Bland-Altman the differences is constant in increasing values on the plot. In Table 3 only small changes in mean bias was x-axis, both for CAP and VEN-values. The bias in CAP found when GEM values were 0–2 mmol/L and 2– is lower than in VEN, but for values below 2 mmol/L 3.5 mmol/L (Fig. 2). Our results show a low accuracy and between 2 and 2.5 mmol/L bias is more stable for with CAP, as well as with VEN analyzed with the hand- VEN (Table 3). held AP compared to the reference method GEM. This is in discrepancy to Baldari [6] and Pyne et al. [7] who Limitations investigated the reliability of the AP in young healthy Time between sample and analysis was seconds for the athletes and where the results showed a good linear rela- handheld analyzer. The blood samples were collected tionship with the reference method using capillary blood upon arrival by two nurses (authors 1 and 4) using the samples. Pattharanitima et al. [8] also showed a high cor- same procedure for all patients included. No local injuries relation between arterial and capillary lactate values, as or issues in the limbs where the samples were collected well as high correlation between arterial and central ven- where found for any of the patients included in the study ous lactate values in 30 septic inhospital patients using during the stay at the emergency ward. All samples tested AP. Our results concur with Datta et al. [11] who demon- with GEM were analyzed within 20 min (30 min stipu- strated a poor agreement of capillary lactate analyzes in lated by manufacturer). We consider our bias concerning comparison to peripheral venous lactate measurements. differences in sampling procedures minute. a b Fig. 2 a, b The Bland-Altman plots describes the level of agreement between the CAP/VEN measurements and the reference method. The Y-axis represents the differences between CAP/VEN and GEM. The X axis represents the mean of CAP/VEN and GEM. The dotted lines displays mean of the differences and the 95% limits of agreements Stoll et al. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine (2018) 26:47 Page 5 of 5 As shown in Table 1 the majority (91,2%) of the in- gas analysis for emergency patients, has been read and approved by all named authors and that there are no other persons who satisfied the criteria cluded patients were triaged orange/yellow and only a for authorship. We further confirm that the order of authors listed in the few red patients could be included. This may have se- manuscript has been approved by all of us. The manuscript has not been lected a category of patients with similar lactate levels published, or submitted for publication elsewhere. Unfortunately, one of the authors (author number four) has recently died (2017). and minimized the spread of our measurements. The discrepancy to the results found by Baldari [6] and Pyne Ethics approval and consent to participate et al. [7] who investigated capillary samples in young The study was approved by the regional committee for medical and health research ethics at Umeå (Ref. 2014–14-31 M). Each participant was given a healthy athletes and Pattharanitima et al. [8] who ana- verbal and written information of the study. All participation was voluntarily lyzed capillary samples from septic patients could per- and a written consent to participate was obtained prior to inclusion. haps be explained by the difference in the selection of Competing interests patients. Where our study had a relatively large number The authors declare that they have no competing interests. of patients (n = 160 triaged mainly as orange/yellow pri- ority) with a similar level of lactate the Baldari study [6] Publisher’sNote showed a wider range of lactate levels. The red/orange Springer Nature remains neutral with regard to jurisdictional claims in patients included with possible low blood-pressure may published maps and institutional affiliations. have had peripheral vasoconstriction. This may account Author details for differences between VEN and CAP levels. 1 Ambulance Services, Sundsvall Hospital, Västernorrland County Council, 851 We found that lactate levels measured with CAP, as 86 Sundsvall, Sweden. Research and Development, Sundsvall Hospital, Västernorrland County Council, Sundsvall, Sweden. Karolinska Institutet, well as VEN, were higher than the values measured with Department of Physiology and Pharmacology, Stockholm, Sweden. GEM (Fig. 2). The spread of 2 mmol/L above values an- alyzed by GEM was more frequent for CAP than for Received: 20 December 2017 Accepted: 14 May 2018 VEN. Baldari et al. [6] found that the deviation with the handheld compared to stationary blood-gas analyzers es- References calated with higher lactate values. The measured levels 1. The National Association of Emergency Medical Technicians, NAEMT PHTLS. Prehospital trauma life support. 7th ed. St. Louis: Elsevier Mosby; 2011. of lactate in our study were generally lower than 2. Widgren B, Jourak M. Medical emergency triage and treatment system 6 mmol/L which gives a small spread of the results and (METTS): a new protocol in primary triage and secondary priority decision in may account for our small deviation from reference. Fur- emergency medicine. J Emerg Med. 2011;40:623–8. 3. Goyal M, Pines JM, Drumheller BC, Gaieski DF. Point-of-care testing at ther studies with patients in critical conditions with a triage decreases time to lactate level in septic patients. J Emerg Med. wider spread of lactate levels are needed to be able to 2010;38:578–81. fully evaluate the potential use of CAP samples. 4. Slomovitz BM, Lavery RF, Tortella BJ, Siegel JH, Bachl BL, Ciccone A. Validation of a hand-held lactate device in determination of blood lactate in critically injured patients. Crit Care Med. 1998;26:1523–8. Conclusion 5. Jansen TC, van Bommel J, Mulder PG, Rommes JH, Schieveld SJ, Bakker J. Our results demonstrate low accuracy and relatively low The prognostic value of blood lactate levels relative to that of vital signs in the pre-hospital setting: a pilot study. Crit Care. 2008;12:R160. precision with VEN / CAP measurements of lactate com- 6. Baldari C, Bonavolonta V, Emerenziani GP, Gallotta MC, Silva AJ, Guidetti L. pared to reference GEM. Our results also suggest that VEN Accuracy, reliability, linearity of Accutrend and lactate pro versus EBIO plus are safer than CAP measurements because of its better analyser. Eur J Appl Physiol. 2009;107:105–11. 7. Pyne DB, Boston T, Martin DT, Logan A. Evaluation of the lactate pro blood precision. lactate analyser. Eur J Appl Physiol. 2000;82:112–6. 8. Pattharanitima P, Tongyoo S, Ratanarat R, Wilachone W, Poompichet A, Abbreviations Permpikul C. Correlation of arterial, central venous and capillary lactate AP: Accutrend plus; CAP: Capillary; GEM: GEM premier 4000; VEN: Venous levels in septic shock patients. J Med Assoc Thail. 2011;94(Suppl 1):175–80. 9. Walter SD, Eliasziw M, Donner A. Sample size and optimal designs for Funding reliability studies. Stat Med. 1998;17:101–10. This study was supported by grants from Emil Andersson foundation for 10. Bland JM, Altman DG. Statistical methods for assessing agreement between medical research and comity for patient safety/Research and Development, two methods of clinical measurement. Lancet. 1986;8:307–10. Västernorrland County Council. 11. Datta D, Grahamslaw J, Gray AJ, Graham C. Capillary and venous lactate There has been no significant financial support for this work that could have agreement: a pilot prospective observational study. Emerg Med J. 2017;34: influenced its outcome. 195–7. Availability of data and materials Please contact the corresponding author for data request. Authors’ contributions Lactate measurement prehospitally has a potential to be one of the important tools in the triage of trauma patients and may help to decide the correct destination. This manuscript is a contribution to the clinical experience of one the lactate device available. All authors planned the study, discussed the presentation of data and approved the final draft. DS and SV collected the data. We confirm that the manuscript, Capillary and venous lactate measurements with a handheld device compared to venous blood-

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Scandinavian Journal of Trauma, Resuscitation and Emergency MedicineSpringer Journals

Published: Jun 5, 2018

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