Frequency, aetiology and outcome of hypernatraemia in hospitalised patients in Umtata, Transkei, South Africa.

OBJECTIVE

To study the frequency, aetiology and outcome of hypernatraemia in adult hospitalised patients.

DESIGN

Retrospective hospital-based study of hypernatraemia using laboratory data to identify patients.

OUTCOME MEASURES

Fluid intake, mortality, neurological signs and symptoms, serum sodium concentration.

RESULT

The overall incidence of hypernatraemia was 1.4%. Among the 98 patients (mean age 44.6 years), head injury (30%), diabetes mellitus (22%), infection (13%) and gastro-intestinal disturbances (13%) were the principal aetiological conditions occurring in more than 75% of all hypernatraemic patients. Hypernatraemia was observed in both the young and the elderly. The overall mortality was high (56%), with significantly higher values in patients over the age of 44 years (66%) and those with serum sodium values greater than 165 mmol/L. Hospital-acquired hypernatraemia was more frequently (59%) observed than admission hypernatraemia (41%). Forty seven per cent of patients had no access to water, 31% were on diuretic therapy whilst solute diuresis was associated with hypernatraemia in 33%. Forty six per cent of patients were clinically dehydrated. Serum sodium levels normalised in more than half the patients (56%). Persistent hypernatraemia was associated with higher mortality. Though neurological signs and symptoms were observed in twelve per cent of patients, it was not associated with higher mortality.

CONCLUSIONS

Hypernatraemia was observed in both the young and elderly and was associated with a high mortality. Hospital-acquired hypernatraemia was more frequently observed and was found to result from inadequate and inappropriate administration of fluids to patients with impaired thirst or restricted free water intake or both. Severe hypernatraemia appeared to be an indicator of poor prognosis.