Diuretics and Electrolyte Disturbances in 1000 Consecutive Geriatric Admissions

Abstract

Old people are commonly receiving diuretics on admission to hospital. Diuretics are recognized as a risk factor for electrolyte disturbances; controversy exists about the relative risks of different combinations (in particular, co-amilozide [Moduretic]). We recorded the drug history and serum electrolytes in 1000 consecutive admissions to a geriatric hospital, and examined the relative prescribing rates of various diuretics in the community. Full results were obtained in 929 patients. A history of diuretic prescription was present in 353 (38%) of the patients; the mean serum sodium in this group (95% CI 136.0–137.1 mmol/1) was lower than in the 586 not prescribed diuretics (137.1–137.9 mmol/1). The difference was small but statistically significant (95% CI difference=0.3–1.6 mmol/1; P<0.01). Hyponatraemia (serum sodium < 130 mmol/l) was not significantly commoner in the 41 patients prescribed co-amilozide than in patients prescribed other diuretics. In general patients prescribed potassium-retaining diuretics had a lower serum sodium than the others. There was a significant positive correlation between the serum potassium and the log [serum urea) (r=0.26, P < 0.001) and a weak negative correlation existed between sodium and potassium (r= −0.14; P < 0.001). There was an association between the prescription of potassium-retaining diuretics and a higher serum potassium; also an association between the prescription of a loop or thiazide diuretic and a lower serum potassium. These interactions were shown by multiple regression analysis to be independent and additive. Co-amilozide formed a significantly higher proportion of all diuretics prescribed in the community group than in the inpatient group (18% versus 12%; P < 0.05). Hyponatraemia was mild and mainly associated with potassium-retaining diuretics in our patients. Our study was unable to confirm or refute any specific dangers of co-amilozide compared with other potassium-retaining diuretic combinations.