Abstract P187: Incidence and Predictors of Diuretic-Induced Hyponatremia

Hyponatremia is a common adverse effect of diuretic use. The purpose of this study was to determine the incidence of Diuretic-induced hyponatremia (DIH) (serum sodium <133mEq/L) caused by commonly used diuretics for treatment of hypertension, specifically, chlorthalidone, hydrochlorothiazide and spironolactone. Electronic health records of outpatients seen at UAB over the last 3 years were reviewed. Inclusion criteria included treatment with one or more of the above mentioned diuretics and having normal sodium levels before and after the hyponatremic episode. Exclusion criteria included heart failure, liver cirrhosis, adrenal insufficiency or an estimated glomerular filtration rate (eGFR) of < 30 mL/min/1.73 m2. The cohort constituted of 270 patients. Based on the total number of prescriptions for each medication, the incidence of DIH was 3.6% for chlorthalidone (48 out of 1322), 3% for spironolactone (35 out of 1159), 1.7% for hydrochlorothiazide (178 out of 10660), while 9 developed hyponatremia on 2 diuretics. Only 57 patients normalized sodium levels after discontinuation of the diuretic, while 213 had normalization of sodium levels despite continuation of the diuretic. Individuals whose sodium levels returned to normal after the diuretic was stopped had lower sodium levels during the hyponatremic episode compared to those who continued the diuretic (129.3±3.9 vs. 130.4±2.0, p=0.002). Older age, Caucasian race, lower baseline sodium levels and lower eGFR values were all risk factors for developing DIH. In this retrospective study, 79% of the patients who developed hyponatremia on diuretics had normalization of serum sodium levels without stopping the diuretic.