Clinical Practice and Cases in Emergency Medicine

Introduction: Hyponatremia is a common and often vexing electrolyte abnormality seen in the emergency setting. The severity of a patient’s symptoms is often dictated by the acuity of hyponatremia development and degree of serum sodium deficit, with patients typically demonstrating more severe neurological symptoms in acute-onset severe hyponatremia. Patients prescribed chlorthalidone are at particular risk of developing hyponatremia, especially in the setting of a secondary insult.

Case Report: We describe two patients presenting to the emergency department with severe hyponatremia who were taking chlorthalidone. Both patients had clinical symptoms that were mild given the degree of their hyponatremia. Additionally, each patient had a secondary insult affecting their volume status that was an important contributing factor in the development of hyponatremia.

Conclusion: Thiazide diuretic use, particularly chlorthalidone, is an important consideration when evaluating patients with new-onset hyponatremia, especially in the setting of excess volume losses or increased consumption of water. These cases demonstrate how patients with severe hyponatremia can present with atypical or mild clinical symptoms and often do not demonstrate significant neurological symptoms such as seizures.