Correspondence / American Journal of Emergency Medicine 34 (2016) 746-755 753

Lukasz Szarpak, PhD, EMT-P, DPH Zenon Truszewski, PhD, MD* Marcin Madziala, MSC Department of Emergency Medicine

Medical University of Warsaw, Warsaw, Poland

*Corresponding author. Department of Emergency Medicine Medical University of Warsaw, 4 Lindleya Str 02-005 Warsaw, Poland. Tel.: +48 502258562 E-mail address: [email protected]

Lukasz Czyzewski, PhD, RN

Department of Nephrologic Nursing Medical University of Warsaw, Warsaw, Poland

http://dx.doi.org/10.1016/j.ajem.2016.01.030

References

1. Bilge S, Aydin A, Eryilmaz M. Endotracheal intubation with tactical fiberoptic imaging systems. Am J Emerg Med 2015;34(3):664-5. http://dx.doi.org/10.1016/j.ajem.2015.12. 061.
2. Truszewski Z, Bogdanski L, Kurowski A, Czyzewski L, Stepniewska W, Stawicka I, et al. Does the Venner A.P. Advance video laryngoscope improve success of first intubation attempt of trauma patient? Am J Emerg Med 2015;34(2):315-6. http://dx.doi.org/10. 1016/j.ajem.2015.10.058.
3. Frerk C, Mitchell VS, McNarry AF, Mendonca C, Bhagrath R, Patel A, et al. Difficult Air- way Society 2015 guidelines for management of unanticipated difficult intubation in adults. Br J Anaesth 2015;115(6):827-48. http://dx.doi.org/10.1093/bja/aev371.
4. Truszewski Z, Szarpak L, Czyzewski L, Evrin T, Kurowski A, Majer J, et al.A comparison of the ETView VivaSight SL against a fiberoptic bronchoscope for Nasotracheal intubation of multitrauma patients during resuscitation. A randomized, crossover, manikin study. Am J Emerg Med 2015;33(8):1097-9. http://dx.doi.org/10.1016/j.ajem.2015.04.078.
5. Barak M, Assalia A, Mahajna A, Bishara B, Braginski A, Kluger Y. The use of VivaSight(TM) single lumen endotracheal tube in morbidly obese patients undergoing laparoscopic sleeve gastrectomy. BMC Anesthesiol 2014;14:31. http://dx.doi.org/10.1186/ 1471-2253-14-31 [Published online 2014 May 5].

   Potassium measurement in the ED: interpret with caution

   

   To the Editor,

   We read with interest the article of Acikgoz et al [1], who showed that the concentration of potassium measured in serum by a conven- tional clinical chemistry analyzer was significantly and consistently higher than that measured in paired samples by means of a Blood gas analyzer. However, we raise some doubts as to whether these results may be considered clinically and analytically meaningful. First, in this study, it is stated that potassium was measured in serum using a blood gas analyzer placed in the emergency department (ED). This is in- deed unusual, wherein Blood gas analyzers typically use whole blood as biological matrix, and it seems rather weird and unpractical that sample separation for obtaining serum could have been performed in the ED. On the other hand, if potassium was measured in whole blood using the blood gas analyzer, then a rather reasonable explanation does exist for the discrepancy. The concentration of potassium largely differs in whole blood samples, lithium-heparin plasma, and serum [2]. This is mainly attributable to the fact that blood coagulation triggers release of both potassium and calcium from corpuscular blood elements, namely, platelets, which are physiologically activated upon generation of the blood clot [3,4]. More specifically, up to 10% of the concentration of serum potassium can be explained by the platelet count [3], whereas up to 19% of potassium level can be explained by red blood cell size (ie, the mean corpuscular volume) [4]. It is hence predictable that the concentration of potassium measured in whole blood by means of blood gas analyzers may be consistently lower than, and not necessarily related to, serum potassium values measured using conventional

   clinical chemistry analyzers. Another important issue, which is not ade- quately described in the study of Acikgoz et al, is the potential impact of in vitro hemolysis. Samples collected in dedicated syringes for arterial blood gas analysis are much vulnerable to erythrocyte injury than those drawn by means of traditional blood collection devices, wherein forced aspiration and the use of small needles are 2 of the leading causes of in vitro hemolysis [5]. A direct comparison of Potassium levels in whole blood (or plasma) and serum is hence misleading, wherein we strongly recommend that specific reference ranges should be adopted to prevent misdiagnosis of hyperkalemia in samples drawn for blood gas analysis [2]. The forthcoming commercial introduction of innovative blood gas analyzers equipped with sensors designed to timely and reli- ably identify hemolysis (either in vivo or spurious) in whole blood is an- other valuable perspective for limiting the potential disagreement between ED and laboratory measurement of potassium [6].

   Gianfranco Cervellin, MD Emergency Department, Academic Hospital of Parma, Parma, Italy Corresponding author at: Emergency Department

   Academic Hospital of Parma, 43126 Parma, Italy Tel.: +39 0521703800; fax: +39 0521703144

   E-mail addresses: [email protected], [email protected]

   Giuseppe Lippi, MD

   Section of Clinical Biochemistry, University of Verona, Verona, Italy

   http://dx.doi.org/10.1016/j.ajem.2016.01.029

   References

   Acikgoz SB, Genc AB, Sipahi S, Yildirim M, Cinemre B, Tamer A, et al. Agreement of serum potassium measured by blood gas and biochemistry analyzer in patients with moderate to Severe hyperkalemia. Am J Emerg Med 2016. http://dx.doi.org/10. 1016/j.ajem.2016.01.003 [in press].

6. Asirvatham JR, Moses V, Bjornson L. Errors in potassium measurement: a laboratory perspective for the clinician. N Am J Med Sci 2013;5(4):255-9.
7. Lippi G, Salvagno GL, Guidi GC. Adjustment of serum potassium for age and platelet

   count. A simple step forward towards personalized medicine. Clin Chem Lab Med 2015;53:e325-7.

   Lippi G, Salvagno GL, Guidi GC. Mean corpuscular volume and red blood cell distribu-

   tion width are independent predictors of Serum potassium concentration in healthy individuals. Clin Chim Acta 2015;446:117-8.

   Lippi G, Plebani M, Di Somma S, Cervellin G. hemolyzed specimens: a major challenge for emergency departments and clinical laboratories. Crit Rev Clin Lab Sci 2011;48: 143-53.

8. Weng CW, Hsieh BC, Hou YT, Cheng TJ. Determination of hematocrit by voltage- induced hemolysis on a disposable electrochemical sensing strip. Analyst 2015;140: 6619-24.

   Reply to “Potassium measurement in the ED:

   

   interpret with caution”

   To the Editor,

   We thank Cervellin and Lippi for their interest in our article [1] in which we assessed the agreement of potassium values measured by central laboratory biochemistry analyzer and blood gas analyzer. The authors state that we had studied blood gas samples in a point-of-care device placed in the emergency department (ED). Actually, we did not report such a thing in the Methods section, and all blood gas samples were sent for analysis to the biochemistry laboratory; our blood gas an- alyzer was placed in the central laboratory, as well. Thus, sample sepa- ration was not performed in the ED. Moreover, as usual, our blood gas analyzer device also uses whole blood samples. According to our results, there really appears a significant and consistent difference between the 2 measurement methods. As clinicians, we do not delve into the techni- cal details of the individual machines that perform the potassium