Frequency and Severity of Chlorothiazide-Induced Hyponatremia in the Neonatal Intensive Care Unit

Although thiazide diuretics are commonly used in the neonatal intensive care unit (NICU), the risk of thiazide-induced hyponatremia in infants has not been well documented. The primary objective of this study was to determine the frequency and severity of hyponatremia in neonates and infants receiving enteral chlorothiazide. Secondary objectives included identifying: (1) percent change in serum sodium from before chlorothiazide initiation to nadir, (2) time to reach nadir serum sodium concentration, and (3) percentage of patients on chlorothiazide receiving sodium supplementation.

This was a retrospective cohort study of NICU patients admitted between July 1, 2014, and July 31, 2019, who received ≥1 dose of enteral chlorothiazide. Mild, moderate, and severe hyponatremia were defined as serum sodium of 130 to 134 mEq/L, 120 to 129 mEq/L, and less than 120 mEq/L, respectively. Data including serum electrolytes, chlorothiazide dosing, and sodium supplementation were collected for the first 2 weeks of therapy. Descriptive and inferential statistics were performed in SAS software, Version 9.4.

One hundred and seven patients, receiving 127 chlorothiazide courses, were included. The median gestational age at birth and postmenstrual age at initiation were 26.0 and 35.9 weeks, respectively. The overall frequency of hyponatremia was 35.4% (45/127 courses). Mild, moderate, and severe hyponatremia were reported in 27 (21.3%), 16 (12.6%), and 2 (1.6%) courses. The median percent decrease in serum sodium from baseline to nadir was 2.9%, and the median time to nadir sodium was 5 days. Enteral sodium supplements were administered in 52 (40.9%) courses. Sixteen courses (12.6%) were discontinued within the first 14 days of therapy due to hyponatremia.

Hyponatremia occurred in over 35% of courses of enteral chlorothiazide in neonates and infants. Given the high frequency of hyponatremia, serum sodium should be monitored closely in infants receiving chlorothiazide. Providers should consider early initiation of sodium supplements if warranted.

· One-third of infants on chlorothiazide develop hyponatremia.. · Nadir serum sodium typically occurs within 5 days.. · Monitor sodium closely after chlorothiazide initiation..