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.