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 .
Keywords: critical care; intensive care unit; potassium.