Abnormalities of Water Metabolism after Surgery for Optic/Chiasmatic Astrocytomas in Children

Abstract

A major concern during the early postoperative period after surgical resection of optic chiasmatic gliomas is the derangement of sodium and water metabolism which may add to the morbidity of the procedure. The purpose of this study was to characterize the abnormalities of water and sodium metabolism in children with optic chiasmatic gliomas treated surgically at British Columbia’s Children’s Hospital and to identify therapeutic modalities which might prevent or ameliorate the development of these complications. A retrospective chart review of children with optic/chiasmatic gliomas undergoing operations on the tumor was performed and the pre- and postoperative radiographs reviewed by an independent neuroradiologist. There were 11 patients who underwent 13 operations for either resection (n = 9) or biopsy (n = 4) of their optic chiasm tumor. The extent of resection in patients undergoing more than simple biopsy ranged from 83 to 99%, and all patients with resection had exophytic tumor extending into the hypothalamus. Postoperative syndrome of inappropriate antidiuretic hormone secretion (SIADH) and/or diabetes insipidus occurred after 8 of the 9 tumor resections and was associated with significant morbidity. No disturbance of water metabolism occurred after biopsy only. In patients with SIADH, the urinary sodium level rose markedly 6–12 h prior to the development of hyponatremia, and it was concluded that this was a valuable predictor of impending hyponatremia. Replacement of urine output was noted to be the most reliable way to avoid rapid fluctuations in serum sodium and to avoid the morbidity of diabetes insipidus or SIADH and is recommended in the postsurgical patients who cannot regulate fluid intake.