Long-term Mortality Outcomes of Hyperkalemic Patients in the Emergency Department Setting: A Case Control Study

Abstract

Background: The impact of an episode of hyperkalemia on long term mortality is not well studied. Such a study is vital for development of a utilization strategy for new drugs for the treatment of hyperkalemia. To study the long term impact of hyperkalemia on mortality, we conducted a retrospective, observational casecontrol study in a tertiary care emergency department. We compared cases of non-hemolyzed serum potassium >5.3 mEq/L with normokalemic controls. Allcause mortality and causes of death were determined from social security death index, national death index, and medical record review over a follow-up period of 490 patient years. Methods and Findings:A total of 287 consecutive subjects (223 cases, 64 controls) were identified among 14,483 patients. Cox proportional hazard regression showed that for each 1 mEq/L increase in admit potassium, all-cause mortality Hazard Ratio was 1.54, 95% Confidence Interval: 1.22-1.96. Subgroup analyses showed higher mortality in acute kidney injury and heart failure patients. Conclusion:Hyperkalemia predicted all-cause mortality, when adjusted for age, sex, Charlson comorbidity index, and significant covariates (heart failure and end stage renal disease). The deleterious effect of admit hyperkalemia persisted in survivors from index episode throughout the study period. Cardiovascular mortality was statistically more prevalent. Future studies are needed for risk stratification strategies and mortality impact of newer drugs.