Serum potassium levels and outcomes in critically ill patients in the medical intensive care unit

OBJECTIVE: To compare the outcomes of patients with and without a mean serum potassium (K(+)) level within the recommended range (3.5–4.5 mEq/L). METHODS: This prospective cohort study involved patients admitted to the medical intensive care unit (ICU) of Siriraj Hospital from May 2012 to February 2013. The patients’ baseline characteristics, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, serum K(+) level, and hospital outcomes were recorded. Patients with a mean K(+) level of 3.5 to 4.5 mEq/L and with all individual K(+) values of 3.0 to 5.0 mEq/L were allocated to the normal K(+) group. The remaining patients were allocated to the abnormal K(+) group. RESULTS: In total, 160 patients were included. Their mean age was 59.3±18.3 years, and their mean APACHE II score was 21.8±14.0. The normal K(+) group comprised 74 (46.3%) patients. The abnormal K(+) group had a significantly higher mean APACHE II score, proportion of coronary artery disease, and rate of vasopressor treatment. An abnormal serum K(+) level was associated with significantly higher ICU mortality and incidence of ventricular fibrillation. CONCLUSION: Critically ill patients with abnormal K(+) levels had a higher incidence of ventricular arrhythmia and ICU mortality than patients with normal K(+) levels.