Prognostic significance of admission electrolyte disturbances in older people: A retrospective cohort study

Abstract

The purpose of this study was to investigate the prevalence and survival of elderly patients with extreme electrolyte disturbance on admission. A retrospective cohort of 986 acutely admitted elderly were screened in an acute geriatric unit in a regional hospital. One hundred and four patients with admission sodium or potassium disturbances (serum Na, <125 mmol/L or >147 mmol/L; serum K, <2.6 mmol/L or >5.5 mmol/L) and 104 sex‐matched controls were studied. Demographic data were recorded. Prevalence of electrolyte abnormalities, survival at index admission, 90, 180, 270 and 360 days after index admission were calculated. Of the acute admissions, 10.6% had extreme electrolyte disturbances. Elderly women had higher risk (relative risk, 1.68; 95% confidence interval, 1.07–2.64). Hypernatremia, hyperkalemia and hypokalemia were independent risk factors for mortality at index admission while hyponatremia was not. Hyponatremia started to predict mortality 90–270 days after the index admission. Extreme admission electrolyte disturbances were a common occurrence in the acutely ill elderly. Hypernatremia, hyperkalemia and hypokalemia were predictors of immediate mortality while hyponatremia was a long‐term survival prognostic indicator.