Acute Hyperkalemia and 30-Day Mortality: Increased Mortality at Slightly Elevated Plasma Potassium Levels

BackgroundPotassium is involved in multiple physiological processes in the body, and hyper-kalemia is a common, potentially life-threatening condition. ObjectiveThe aim of our study was to examine the association between plasma potassium levels, and 30-day mortality in patients presenting to an emergency department with normo- or hyperkalemia. DesignRetrospective Cohort study. SettingEmergency Departments in the Capital region of Denmark ParticipantsPersons attending Emergency Departments in the Capital Region of Denmark from 2017-2021 with a plasma potassium level of at least 3.5 mM measured within 4 hours after arrival. MeasurementsThe study was based on data from Danish National Registries and electronic patient records. We performed Kaplan-Meier survival analyses and unadjusted and adjusted cox regression analyses utilizing plasma [K+] 3.5-4.4 mM as the reference group for 30-day mortality hazard ratios (HRs). ResultsA total of 248,453 patients were included with a median age of 60 years (Q1;Q3 42;75), and 6,959 (2.8%) died within 30 days. Mortality was 2.2% for potassium level 3.5-4.4 mM, 6.9% for 4.5-4.9 mM, 17.1% for 5.0-5.9 mM, and 26.9% for [≥]6.0 mM. Unadjusted 30-day HRs were 3.2 (95%CI: 3.0-3.4) for [K+] 4.5-4.9 mM, 8.6 (95%CI: 7.9-9.3) for [K+] 5.0-5.9 mM, and 14.7 (95%CI: 12.5-17.0) for [K+] [≥]6.0 mM. Adjusted HRs were 1.4 (1.3-1.5), 2.10 (1.9-2.3), and 2.4 (2.0-2.8), respectively. LimitationsRisk of residual confounding. Missing data. No access to data regarding in-hospital treatment. ConclusionPlasma potassium levels above 4.4 mM were associated with increased 30-day mortality among patients presenting to emergency departments. Primary funding sourceDepartment of Emergency Medicine, Copenhagen University hospital, Bispebjerg and Frederiksberg Hospital.