Endocrine Abstracts

Introduction: Hyponatraemia is the most common of electrolyte abnormalities. There are numerous factors which may directly cause or contribute to hyponatraemia, including dehydration, concomitant cardiac/hepatic/renal disease, and certain medications, such as diuretics. Hyponatraemia may cause a range of symptoms, depending on the speed and severity of the deficiency. Mild hyponatraemia (>115 mmol/l), can causes malaise, nausea and vomiting. Significant hyponatraemia, [Na⁺]<115 mmol/l, manifests with confusion, seizures, and ultimately coma. Chronic, ‘asymptomatic’ hyponatraemia has been shown to cause gait disturbances, falls and neurocognitive impairment.

Case: A 76-year-old lady was brought into A&E, having been found collapsed at home. GCS was 6/15.She was confused and agitated. She was euvolaemic, and had normal blood glucose. CT-head showed no acute intracranial abnormality. Laboratory work up showed a profound hyponatraemia, Na⁺108. Prior to this admission, her sodium levels were within normal ranges. Full-body CT scan, which showed no neoplastic cause for her hyponatrameia. Her past medical history also included asthma, IHD, and primary hypothyroidism. She was smoker, although she denied any new respiratory symptoms, or weight loss. She reported having commenced indapamide for hypertension one day prior to presentation.

Laboratory work: K+4.2 mmol/l; corrected calcium 2.13 mmol/l, TSH 9.9 mU/l, FT₄ 18 pmol/l. Her urinary osmolality was 475 mOsm/kg; urinary [Na⁺] was 27; serum osmolality, 236, serum cortisol was 761 nmol/l. Indapamide was stopped and she was put onto fluid restriction, with a strict input/output chart. She had regular [Na⁺] checks, which showed gradual improvement in the hyponatraemia: 108 mmol/l on day 0, 111 mmol/l on D1, 120 mmol/l on D2, 127 mmol/l on D3. She was notably less confused and agitated on discharge, and, when reviewed in clinic a 4 weeks later, her symptoms had resolved entirely. More recent biochemistry shows normal sodium.

Conclusion: Diuretics are associated with hyponatraemia. However this is the first reported case of hyponatraemia and encephalopathy after single dose of indapamide.