Hypernatremic dehydration in the elderly on admission to hospital.

Dehydration is the most common cause of fluid and electrolyte disturbances in the elderly. This condition is related to the lack of increase in water intake in the presence of an increased fluid loss. The aim of this study was to evaluate the prevalence of hypernatremic dehydration in elderly patients admitted to the hospital. We retrospectively studied 2,894 subjects admitted to the acute ward of the Geriatric Section of the Department of Medical and Surgical Disciplines of the University of Torino from January 1990 to July 1995. Among them 84 (2.9%) patients, mean age 77.3 +/- 9.8 years, had serum sodium levels and blood urea nitrogen greater than 145 mEq/L and 25 mg/dL respectively with serum creatinine below 3 mg/dL. The prevalence of hypernatremic dehydration increases with age. Only 1.6% of the subjects under 65 years old are affected by this condition, against 5.3% of those over 85 years. The mortality rate observed during hospitalization is 29.8%. Mortality is positively related to serum sodium levels. We found mortality rates of 33.3% and 71.4% respectively in subjects with serum sodium levels from 151 to 153 mEq/L and in those with values over 154 mEq/L. Both serum sodium levels and age are independent risk factors for mortality (O.R. 1.31 and 1.07 respectively).