Preadmission Diuretic Use and Mortality in Patients Hospitalized With Hyponatremia: A Propensity Score-Matched Cohort Study.

BACKGROUND: Hyponatremia is associated with increased mortality and is frequently induced by diuretic use. It is uncertain whether diuretic use is linked to mortality risk in patients with hyponatremia.

STUDY QUESTION: To measure the prognostic impact of diuretic use on 30-day mortality among patients hospitalized with hyponatremia.

STUDY DESIGN: Using population-based registries, we identified all patients with a serum sodium measurement <135 mmol/L within 24 hours after acute hospital admission in western Denmark from 2006 to 2012 (cumulative population of 2.2 million). We categorized patients as current diuretic users (new and long-term), former users or nonusers, and followed them until death, migration or up to 30 days which ever came first.

MEASURES AND OUTCOMES: Thirty-day cumulative mortality and relative risk with 95% confidence interval (CI) controlled for demographics, previous morbidity, renal function, and co-medications. Calculations were also divided by the diuretic type and were repeated after propensity score matching.

RESULTS: Thirty-day mortality was 11.4% among current diuretic users (n = 14,635) compared with 6.2% among nonusers, yielding an adjusted relative risk of 1.4 (95% CI, 1.2-1.5). New users were at higher risk (1.7, 95% CI, 1.5-2.0) than long-term users (1.3, 95% CI, 1.2-1.4). In particular, the use of loop diuretics (1.6, 95% CI, 1.4-1.8), potassium-sparing diuretics (1.6, 95% CI, 1.2-2.2), and diuretic polytherapy (1.5, 95% CI, 1.3-1.7) were associated with increased risk, whereas thiazide use was not (1.0, 95% CI, 0.9-1.2). Propensity score-matched analyses confirmed the results.

CONCLUSIONS: Diuretic use except from thiazides, and particularly if newly initiated, is a negative prognostic factor in patients admitted with hyponatremia.