Association Between Serum Potassium Levels and Cardiac Arrest Risk in Emergency Resuscitation Room Patients: A Retrospective Cohort Study

Background: This study aimed to investigate the association between serum potassium levels and the risk of cardiac arrest in patients admitted to the emergency resuscitation room and to identify the optimal potassium range associated with the lowest risk. Methods: We conducted a retrospective cohort study of 784 adults (384 with cardiac arrest and 400 controls) admitted to the emergency resuscitation room of a tertiary academic medical center between January 2020 and July 2021. Using multivariable logistic regression and restricted cubic spline analysis with four knots, we examined the nonlinear relationship between serum potassium levels and cardiac arrest risk after adjusting for critical confounders including lactate levels and MEWS scores. Results: A robust J-shaped association was observed between serum potassium levels and cardiac arrest risk. The lowest risk occurred within the range of 3.1–4.0 mmol/L, with significantly increased risk both below and above this range. The association remained significant after adjustment for lactate alone (p-nonlinear < 0.001) and after simultaneous adjustment for the MEWS score and lactate (p-nonlinear < 0.05). Serum potassium demonstrated fair predictive accuracy for cardiac arrest with an AUC of 0.709 (95% CI: 0.672–0.747). At the optimal cut-off value of 4.45 mmol/L, specificity reached 87.5% and positive predictive value was 80.4%. Conclusions: This study reveals a consistent J-shaped distribution between serum potassium levels and cardiac arrest risk in emergency resuscitation room patients, with the safest range identified at 3.1–4.0 mmol/L. These findings suggest that maintaining potassium levels in the lower physiological range may be beneficial for preventing cardiac arrest in critically ill emergency patients. Serum potassium assessment provides a valuable tool for risk stratification in resuscitation settings.