Int J Emerg Med (2009) 2:117–120 DOI 10.1007/s12245-009-0091-1 BRIEF RESEARCH REPORT Comparison of the point-of-care blood gas analyzer versus the laboratory auto-analyzer for the measurement of electrolytes Anunaya Jain & Imron Subhan & Mahesh Joshi Received: 8 October 2008 / Accepted: 27 January 2009 / Published online: 24 February 2009 # Springer-Verlag London Ltd 2009 Abstract Background Electrolyte values are measured both by arterial blood gas (ABG) analyzers and central laboratory auto-analyzers (AA), but a significant time gap exists between the availability of both these results, with the ABG giving faster results than the AA. The authors hypothesized that there is no difference between the results obtained after measurement of electrolytes by the blood gas and auto-analyzers. Methods After approval by the ethics committee, an observational cohort study was conducted in which 200 paired venous and arterial samples from patients admitted to the Medical Intensive Care Unit (ICU) of Apollo Hospital, Hyderabad, India, were analyzed for electrolytes on the ABG machine and the AA. Analyses were done on the ABL555 blood gas analyzer and the Dade Dimension RxL Max, both located in the central laboratory. Statistical analyses were performed using paired Student’s t test. Results A total of 200 paired samples were analyzed. The mean ABG sodium value was 131.28 (SD 7.33), and the mean AA sodium value was 136.45 (SD 6.50) (p< 0.001). The mean ABG potassium value was 3.74 (SD 1.92), A. Jain (*) College of Medicine, Mayo Clinic, Rochester, MN, USA e-mail: erjain@yahoo.co.in I. Subhan : M. Joshi Department of Emergency Medicine, Apollo Health City, Hyderabad, India I. Subhan e-mail: imronsubhan@gmail.com M. Joshi e-mail: mahajosh@rediffmail.com and the mean AA potassium value was 3.896 (SD 1.848) (p =0.2679). Conclusion Based on the above analysis, the authors found no significant difference between the potassium values measured by the blood gas machine and the auto-analyzer. However, the difference between the measured sodium was found to be significant. We therefore conclude that critical decisions can be made by trusting the potassium values obtained from the arterial blood gas analysis. Introduction Point-of-care testing enables clinicians to initiate appropri- ate treatment for emergent conditions, thereby benefitting the patient both clinically and economically [1]. Electrolyte values are conventionally measured for all critical patients who present to the emergency department, for patients receiving fluid therapy, and for patients admitted to intensive care units (ICU). Routinely, all electrolytes are measured from serum by the auto-analyzers (AA) available in central laboratories of hospitals; however, this is time-consuming. Typically, a turnaround time of about 15 min is noted on average in acute care laboratories of most tertiary care hospitals for the above [2]. Quick decisions that need to be made depending on electrolyte values hence are often made either blindly or are delayed. Point-of-care testing for electrolytes is avail- able from specialized equipment such as the iSTAT or Stat Profile Critical Care Xpress analyzers [3]. The operational cost of iSTAT and other similar equipment is a major deterrent to their utilization in developing systems of health care. Electrolytes are also measured during arterial blood gas analysis, but are traditionally rarely trusted for clinical decision-making because of the dearth of published