A descriptive study of hyponatremia in a tertiary care hospital of Eastern India

Hyponatremia is one of the commonest electrolyte disturbances encountered in medical wards and contributes to substantial morbidity and mortality. However, early recognition and management drastically alters prognosis. Therefore, this observational study was taken up to explore the clinical profile of hyponatremia.

To assess the incidence and clinical profile of hyponatremia in medically ill patients.

This observational study was conducted in the medical ward of a tertiary care hospital from March 2010 to April 2011. All patients underwent routine hemogram, blood biochemistry, serum electrolytes, thyroid function tests, and morning serum cortisol estimation. This was followed by a plasma and urinary osmolality determination (osmometer 800 CL) as well as urinary sodium estimation. Patients were diagnosed to have syndrome of inappropriate antidiuretic hormone secretion (SIADH) if they satisfied the Bartter and Schwartz criteria.

201 patients (16.4%) had a serum Na < 135 meq/l. There were 126 (62.69%) male patients and 75 (37.31%) female patients. Severe hyponatremia (Na < 120 meq/l) was detected in 30 patients (2.4%). The largest group of hyponatremic patients were euvolemic [102 (50.74%)], followed by hypervolemic [54 (26.86%)] and hypovolemic [45 (22.4%)]. Sixty-six patients fulfilled the criteria for SIADH. The most common underlying predisposing factor for hyponatremia in our case series was fluid loss by vomiting/diarrhea. During the hospital stay, 13.5% (15/201) hyponatremic patients died, while the corresponding figure in normonatremic patients was 8.5% (87/1020).

The incidence of hyponatremia in our series was higher than values mostly reported in western literature. Euvolemic hyponatremia was the most common type, a significant fraction of which is SIADH.