Acute Hyponatremia After a Religious Fast

Our objective is to describe how polydipsia and intake of nonsteroidal anti-inflammatory drugs (NSAIDs) after fasting while breastfeeding may result in acute symptomatic hyponatremia.

We present the case of a 24-year-old woman at 4 weeks postpartum who engaged in a 20-hour fast from both eating and drinking, during which she continued to breastfeed her newborn child. After ending her fast, she noted decreased milk supply. Attributing her decreased milk supply to dehydration, she then consumed 4 L of water with little salt and also took NSAIDs for a headache, which continued to worsen. Upon presentation to the emergency department, she was found to have a sodium level of 124 mEq/L (normal, 135-145 mEq/L) and a urine specific gravity of 1.015 (normal, 1.005 - 1.030). Thyroid function and cortisol level test results were normal. She was diagnosed with acute symptomatic hypovolemic hyponatremia. After 1 L of normal saline her sodium rapidly corrected to normal and her symptoms resolved. At 2 months of follow-up she was asymptomatic and had no further episodes of hyponatremia.

Due to the patient's gender and small body size, 4 L of water was sufficient to lower her serum sodium rapidly from normal to 124 mEq/L. She was unable to excrete this water due to a combination of hypovolemia-mediated arginine vasopressin and NSAID use.

Clinicians should be cognizant that reproductive-age women are uniquely susceptible to hyponatremia and dangerous sequelae therein. They should counsel fasting individuals, particularly lactating women, to consume solute as well as fluid after fasting.