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

Background: Potassium is involved in multiple physiological processes in the body, and hyperkalemia is a common, potentially life-threatening condition. Objective: The 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. Design: Retrospective Cohort study. Setting: Emergency Departments in the Capital region of Denmark Participants: Persons 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. Measurements: The 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). Results: A 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. Limitations: Risk of residual confounding. Missing data. No access to data regarding in-hospital treatment. Conclusion: Plasma potassium levels above 4.4 mM were associated with increased 30-day mortality among patients presenting to emergency departments. Primary funding source: Department of Emergency Medicine, Copenhagen University hospital, Bispebjerg and Frederiksberg Hospital.