RESUMEN
To determine the etiology of hyponatraemia, the treatment instituted and the outcome of treatment in a tertiary care hospital setting. Case series. The Aga Khan University Hospital, Karachi, between January and June 2004. Case records of 220 patients admitted to the medical service were identified through computerized hospital patients' data. All patients >/= 15 years with a sodium level on admission of 10 mmol/L/ 24 hours in 17% patients. The average duration of stay was 4 days. The mortality was 6.8%. Medicines accounted for 30% cases of hyponatraemia, of which diuretics, angiotensin converting enzyme inhibitor [ACEI] and angiotensin receptor blockers [ARBs] were top of the list. Other causes were gastrointestinal in 25%, chest infection in 11% patients, depletional hyponatraemia in 10% patients, SIADH [Syndrome of Inappropriate Antidiuretic Hormone] in 6% patients, congestive cardiac failure and malignancy in 5% each and chronic liver disease in 3.6% patients. Hyponatraemia was seen more commonly in the elderly, major causes being gastrointestinal losses and use of drugs. Serum sodium correction should be less than 10 mmol/L/24 hours. The treatment plan be directed to correction of the underlying cause. Diagnosis of SIADH should be sought with appropriate investigation