Serum and Urine Sodium in Dengue Patients

We evaluated serum and urine sodium levels in children with dengue infections. Children with acute febrile illness admitted to Bhumibol Adulyadej Hospital in Bangkok from January 1999 to January 2000 were enrolled. Serum and urine sodium levels were measured before initiating intravenous fluid therapy. Two milliliters of blood were obtained on admission and before discharge to test for anti-dengue virus antibody using the enzyme-linked immunosorbent assay technique. Hyponatremia was defined as a serum sodium level <130 mEq/l and depletion of circulatory volume was defined as a urine sodium level ≤20 mEq/l. Out of 93 enrolled patients, 49 were categorized as dengue patients and 44 were as non-dengue patients. Six dengue patients developed shock whereas 43 patients did not. The mean serum sodium level was significantly lower in dengue patients compared to non-dengue patients (p-value < 0.0001). Hyponatremia was 9.7 times more common in dengue patients. Among dengue patients, the mean serum sodium level was significantly lower in shock patients compared to non-shock patients (p-value = 0.003). However, the prevalence of hyponatremia was not different between the two groups. The mean urine sodium level was significantly lower in dengue patients compared to non-dengue patients (p-value <0.0001). A urine sodium level ≤20 mEq/l was 8.1 times more common in dengue patients. Among dengue patients, the mean urine sodium level was not significantly different between shock and non-shock patients. In shock patients, a urine sodium level ≤20 mEq/l was 7.6 times more common. MATERIALS AND METHODS The study was conducted in the Department of Pediatrics at Bhumibol Adulyadej Hospital, which is a tertiary and large teaching hospital in Bangkok, Thailand. From January 1999 to January 2000, all hospitalized children aged 0-15 years with acute febrile illnesses who presented with a body temperature ≥37.8oC for ≤3 days without specific cause of infection were enrolled. Dengue infection was diagnosed according to World Health Organization (WHO) criteria with serological confirmation. Children with dengue infection who developed hypotension or a pulse pressure <20 mmHg were categorized as shock patients and the others as non-shock patients. Children diagnosed with other illnesses, malnutrition, chronic hepatic or renal diseases and those who had previously received treatment with antidiuretic drugs and intravascular fluid were excluded. Children with grade 4 dengue hemorrhagic fever were also excluded due to the need for emergent intravenous fluid. SOUTHEAST ASIAN J TROP MED PUBLIC HEALTH 198 Vol 36 No. 1 January 2005 Parents completed informed consent for the children. All patients received treatment as recommended by WHO guidelines. Serum and urine sodium levels were tested before initiating intravenous fluid. Two milliliters of blood were obtained on admission and before discharge from the hospital and the separated serum was stored at -20oC until tested for dengue virus antibody at the Armed Forces Research Institute of Medical Sciences (AFRIMS), Bangkok, Thailand. Demographic data and the clinical manifestations of all the patients were recorded. Hyponatremia was defined as a serum sodium level <130 mEq/ l and depleted circulatory volume (ECV) was defined as a urine sodium level ≤20 mEq/l. Statistics used for analysis included mean, range, and percentage in demographic data. The chi-square test was used to test for differences in population proportions. The Student’s t-test was used to evaluate differences between population means. Odd ratios (OD) and 95% confidence intervals (95%CI) were used to test an association between populations.