EARLY POSTOPERATIVE HYPONATREMIA AFTER SURGERY FOR CRANIOPHARYNGIOMA - A RETROSPECTIVE STUDY OF 21 PEDIATRIC CASES

Hyponatremia is a common postsurgical complication, especially after r emoval of a hypothalamic and/or pituitary lesion, Early postsurgical h yponatremia was studied retrospectively in 21 pediatric patients with a mean age of 6.5 +/- 1.8 years (range, 2-16 years) who underwent a fi rst surgical procedure for craniopharyngioma, There were 12 boys (62 % ) and nine girls (38 %). Hyponatremia (<130 mmol/L) occurred at the en d of the fourth day in 11 patients (52 %). Duration of hyponatremia wa s two and a half days. Seizures occurred in three patients, The cause was release of residual antidiuretic hormone in six cases and acute ad renal insufficiency in the remaining five cases. When the patients who did and did not develop hyponatremia were compared using Student's t tests, serum sodium levels and urinary sodium excretion on the day bef ore the occurrence of hyponatremia were found to significantly predict this complication. Vasopressin and hydrocortisone were used in all th e patients with hyponatremia. Mean intravenous therapy duration was 5. 33 days, and none of the patients had their intravenous line removed b efore the end of the first two days. Mean intravenous sodium dose was 2.72 meq/kg/d. Four patients required mineralocorticoid therapy to pre vent renal sodium wasting; among them, one had severe hyponatremia due to syndrome of inappropriate secretion of antidiuretic hormone (SIADH ). Hyponatremia is a very common complication of craniopharyngioma sur gery that should be routinely looked for by performing simple tests at regular intervals (serum and urinary electrolytes and osmolarity, uri nary output, and fluid/electrolyte balance). The mechanisms involved a re multiple and frequently interlinked: dilution hyponatremia due to i nfusion of hypotonic solutes, renal sodium wasting due to acute adrena l insufficiency, SIADH-like condition due to release of residual ADH, growth hormone deficiency, and perhaps transient hyperproduction of br ain natriuretic peptide (BNP). Treatment should be adjusted based on t he results of simple tests and of assays of plasma renin activity, ald osterone, and BNP.