Review of cases of hyponatraemia in the Port Moresby General Hospital between August 1993 and June 1995.

Hyponatraemia (serum sodium level below 130 mmol/l) is a common electrolyte abnormality in a hospital population. It can be associated with dehydration, overhydration or normal hydration. Clinically, it is important to recognize the common diseases associated with hyponatraemia since correct treatment in terms of fluid replacement is essential in preventing complications of low serum sodium. We have reviewed results of serum sodium tested from patients admitted to the Port Moresby General Hospital between 1993 and 1995. This was aimed at identifying the most common features associated with low sodium. Clinical information and diagnosis were obtained by looking through a series of request forms. Of the approximately 30,000 blood samples taken over 23 months, the percentage of samples with hyponatraemia was about 1%. Hyponatraemia was more common in medical (38%) and paediatric (35%) cases and at the extremes of ages, ie, under the age of 6 years and above 40 years. Over a quarter of the hyponatraemic patients had severe hyponatraemia (serum sodium below 120 mmol/l). Clinical conditions commonly associated with hyponatraemia, in descending order of importance, were diarrhoea and vomiting, renal failure, central nervous system infections and trauma, pulmonary infections, oedematous states (eg, nephrotic syndrome) and diabetes mellitus.