Inappropriate secretion of antidiuretic hormone in acute bacterial meningitis.

Sixty children aged from 1 month to 12 years (mean (SD) 3.18 (3.49) years) with acute bacterial meningitis were studied for the incidence, clinical manifestations and outcome of the inappropriate secretion of antidiuretic hormone syndrome (SIADH). Serum sodium levels and osmolality of serum and urine were estimated on admission and on days 3 and 10. SIADH was diagnosed in 22 out of 60 cases (36.7%) on admission and in six of 48 cases (12.5%) on day 3. Hyponatraemia without SIADH, attributed to vomiting and fever, was detected in seven cases (11.7%). Serum sodium levels returned to normal within 48 hours in these cases. Serum osmolality and sodium levels took longer to return to normal values in patients with SIADH. However, none of the cases showed any evidence of SIADH on the 10th day. A significant correlation with SIADH was observed in cases with evidence of severe meningeal inflammation (p < 0.001). The incidence of SIADH was highest with Streptococcus pneumoniae (75%), followed by Haemophilus influenzae (57.1%). Overall mortality was 26.7%, and mortality was significantly higher (p < 0.001) in cases with SIADH, all of whom died during the 1st 72 hours. Ten out of 22 cases (45.4%) with SIADH who survived beyond the 1st 72 hours had an uneventful course even though all of them had biochemical evidence of SIADH on the 3rd day. Mortality was quite high also in children with severe malnutrition (75%) and in those with S. pneumoniae as the aetiological organism (75%).