Timing, duration, and severity of hyponatremia following pediatric brain tumor surgery*.

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To describe the time course, variability, and magnitude of serum sodium changes among children undergoing intracranial tumor surgery. Retrospective cohort study. Tertiary children's hospital in Salt Lake City, UT. Children 0-19 years undergoing first neurosurgical procedure for an intracranial tumor, treated during January 2001 and February 2012. None. Three hundred nineteen patients were placed in three exclusive groups based on the lowest serum sodium measurement during admission: 1) severe hyponatremia: serum sodium less than or equal to 130 mEq/L; 2) mild hyponatremia: 131-135 mEq/L; and 3) normal sodium: more than 135 mEq/L. Timing and severity of sodium perturbations were assessed within each group. Hundred thirty-seven patients (43%) had mild hyponatremia, 39 (12%) had severe hyponatremia, and 143 (45%) had normal sodium. After surgery, sodium decreased in all groups with lower averaged concentrations during postoperative days 0-1 and 5-6, although patients with severe hyponatremia had the greatest decline. Nearly 80% of hyponatremic patients had mild hyponatremia prior to development of severe hyponatremia; median time between mild hyponatremia and severe hyponatremia was 1.6 days (interquartile range, 0.4-5.6). Seventy-five percent of patients manifest mild hyponatremia within two postoperative days; however, severe hyponatremia developed later with 75% of patients manifesting severe hyponatremia within six postoperative days. Nine patients had initial severe hyponatremia between days 6 and 20 after surgery. Patients with severe hyponatremia had greater sodium variability with significantly lower nadirs, greater maximum values, and larger decreases within 24-hour periods compared with other sodium groups. Seventy-five percent of children with severe hyponatremia spent more than 4 days with abnormally low sodium values. Among hyponatremic patients, obstructive hydrocephalus and age less than 3.5 years were significant independent risk factors for severe hyponatremia. Hyponatremia developed in just over half of children. Young children with hydrocephalus have increased risk of severe hyponatremia. Those with severe hyponatremia need frequent and prolonged monitoring because of risk for repeat sodium changes. Further study is needed to evaluate ideal monitoring and treatment of severe hyponatremia after intracranial tumor surgery.