Relationship between serum potassium level and survival outcome in out-of-hospital cardiac arrest using CAPTURES database of Korea: Does hypokalemia have good neurological outcomes in out-of-hospital cardiac arrest?

Background. Sudden cardiac arrest is a major cause of death worldwide. Serum potassium level is an initial laboratory test that serves as part of an electrolyte panel easily obtainable by most emergency departments (EDs). Objectives. To evaluate the relationship between serum potassium level and the survival outcome for out-of-hospital cardiac arrest (OHCA) patients. Material and methods. We used the Cardiac Arrest Pursuit Trial with Unique Registration and Epidemiological Surveillance (CAPTURES) database, which made up the OHCA cohort of 27 EDs in Korea from January to December 2014. The inclusion criteria were all OHCA patients in the cohort who had received cardiopulmonary resuscitation (CPR) in the hospital. The patients were excluded if they were transferred from another hospital, had a pre-hospital return of spontaneous circulation (ROSC), or if the potassium level and clinical outcome data were missing or not captured. The main parameter was serum potassium level on ED arrival. According to the serum potassium level, the patients were divided into a hypokalemia group (K+ < 3.5 mEq/L), a normokalemia group (K+ = 3.5-5.4 mEq/L) and a hyperkalemia group (K+ >= 5.5 mEq/L). The primary outcome was neurologically favorable survival discharge. Results. Among the 1,616 patients in the CAPTURES cohort, 913 patients were included in the analysis, of whom 46 patients (5.9%) were assigned to the hypokalemia group, 370 patients (40.5%) were assigned to the normokalemia group and 497 patients (54.4%) were assigned to the hyperkalemia group. The hypokalemia group has a significantly higher percentage of good neurological outcomes (26.1%). There was a significant positive correlation with neurologically favorable survival (odds ratio (OR) = 4.45; 95% confidence interval (95% CI) = 1.67-11.91) and a significant positive correlation with survival discharge (OR = 2.25; 95% CI = 1.05-4.82). Conclusions. In OHCA patients, serum potassium level measured in the hospital showed a significant association with survival outcome. Hypokalemia had a significant association with good neurological outcome and survival discharge.