Hyperkalemia Is Associated With Increased Mortality Among Unselected Cardiac Intensive Care Unit Patients

Background Hyperkalemia has been associated with increased mortality in patients with myocardial infarction, but few data exist regarding hyperkalemia in cardiac intensive care unit ( CICU ) patients. We hypothesize that hyperkalemia is associated with increased mortality in unselected CICU patients. Methods and Results We retrospectively reviewed a historical cohort of 9681 CICU patients admitted from January 2007 to December 2015. Hyperkalemia was defined as admission potassium ≥5.0 mEq/L and hypokalemia as admission potassium <3.5 mEq/L. Multivariate logistic regression was used to determine predictors of in-hospital mortality. Postdischarge survival was assessed using Kaplan-Meier analysis and Cox proportional hazards models. The mean age of included patients was 67±15 years, with 36% females, and in-hospital mortality was 9%. Hyperkalemia occurred in 1187 (12.3%) and hypokalemia occurred in 719 (7.4%) patients. Both patients with hyperkalemia (unadjusted odds ratio, 2.85; 95% CI, 2.40-3.39; P<0.001) and patients with hypokalemia (unadjusted odds ratio, 2.31; 95% CI, 1.85-2.88; P<0.001) were at increased risk of unadjusted in-hospital mortality. After adjustment for illness severity and renal function, only patients with hyperkalemia demonstrated increased risk of in-hospital death (adjusted odds ratio, 1.44; 95% CI, 1.11-1.87; P=0.006). Among hospital survivors, only patients with hyperkalemia had lower postdischarge survival by Kaplan-Meier analysis ( P<0.001). After adjustment for illness severity and renal function, hospital survivors with admission hyperkalemia remained at increased risk for postdischarge mortality (adjusted hazard ratio, 1.20; 95% CI, 1.08-1.34; P<0.001). Conclusions Hyperkalemia on CICU admission is associated with higher in-hospital and postdischarge mortality, independent of renal function and illness severity. These findings emphasize the importance of potassium abnormalities as a risk predictor in patients admitted to the CICU .