Background. The serum electrolyte panel (SEP) is a frequently ordered laboratory test, but it has unproven usefulness in the treatment of dehydrated pediatric patients. Our study purpose was to evaluate the usefulness of routinely ordering a SEP in the treatment of dehydrated pediatric patients receiving intravenous fluids (IVFs).

Methods. Children 2 months to 9 years of age who were receiving IVFs because of dehydration were prospectively studied in a pediatric emergency department (PED). Historical data, physical examination findings, degree of dehydration, and SEP results were recorded. After patient evaluation, attending physicians documented whether they would have ordered a SEP. Outcome measurements included changes in clinical management on the basis of SEP results, as well as correlations of dispositions and unscheduled return visits (URVs) with SEP results.

Results. A total of 182 patients were enrolled in the study. One hundred eleven patients had mild dehydration, 55 moderate dehydration, and 16 severe dehydration. Eighty-eight patients (48%; 95% confidence interval: 41–56%) had ≥1 abnormal SEP value. Clinically relevant findings included bicarbonate levels of <16 mmol/L for 28% of patients, hypoglycemia for 9.9%, hypokalemia for 6.0%, and hypernatremia for 3.0%. The attending physicians predicted that a SEP would be clinically important for 34% of all patients. There was a 58% sensitivity in detecting which children would have clinically significant SEP results. Overall, SEP results changed clinical management in 10.4% of cases. One hundred sixty-five (91%) of the patients were discharged from the PED (including 48 who were initially observed), of whom 7 (3.8%) had URVs to the PED within 72 hours and were given additional IVFs. Seventeen patients were admitted (median: 2.6 days), 2 of whom had URVs after hospital discharge for additional IVFs.

Conclusions. On the basis of initial presentation, attending physicians were poor at predicting which children would have clinically significant SEP results. Low bicarbonate values were correlated with observation unit use but not with hospitalization or URVs. The observation unit provided effective care for a subset of dehydrated patients, avoiding the need for hospitalization. Obtaining a SEP can provide useful information for the treatment of some children receiving IVFs because of dehydration.

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