Admission Potassium / Sodium Ratio Linearly Predicts Mortality Outcome Following an Emergency Medical Admission

Abstract

Background : Disturbance of sodium and potassium chemistry is commonly present during an emergency medical admission; we analyse the interaction of these ions and relate K + / Na + Ratios to hospital mortality outcomes. Methods : All emergency medical admissions between 2002 and 2017 were studied. We log transformed sodium and potassium values and calculated their respective ratios as a predictor of 30-day mortality outcomes using a multivariable logistic model. Results: There were 106,586 admissions in 54,928 patients. Patients with higher K + / Na + ratios at admission were older at 66.5 years (IQR 47.0–79.3) compared with 59.0 years (IQR 39.9–75.5) and more likely to be female (51.9% vs. 45.5%). They had a higher 30-day hospital mortality rate – 5.4% vs 3.5% (p<0.001). Across consecutive deciles of K + , rising admission levels linearly predicted outcomes unlike Na + where falling levels linearly predicted an increased mortality. Disturbed K + / Na + balance (log ratio) was prognostic – 30-day mortality OR 1.12 (95%CI 1.11–1.13). Increasing age predicted an increased likelihood of an abnormal K + / Na + balance. Conclusion: Disturbed K + / Na + is linearly predictive of 30-day hospital mortality and is strongly age associated; possibly it is a consequence of Na + leaving the extracellular space (ECF) and K + transit to the ECF due to impaired cellular membrane homeostatic function.