RESUMEN
In this study, visual evoked potentials [VEPs] were studied in 15 children undergoing surgery for parasellar tumors [12 craniopharyngiomas and 3 chiasmal gliomas]. The preoperative visual function was assessed by a standard ophthalmological work up. VEP was performed at different time intervals during surgery and postoperatively. Anesthesia was induced with fentanyl 2 mu kg-1, followed by diprivan 2 mg kg-1 i.v. and tracium 0.5 mg kg-1 i.v. to facilitate intubation. Anesthesia was maintained using diprivan 0.1 mg kg-1 min-1 using a syringe pump and was adjusted to give the patient 0.1 g kg-1 hr-1 together with 1% sevoflurane and O2. The patients were chemically ventilated to maintain normocapnia PaCO2 [30-35 mmHg]. The hemodynamics [B1 Pr and HR], O2 saturation and body temperature were maintained constant throughout the operation. The equipment used in measuring VEP was LED goggles LS-101J [Nihon Koden]. Averages were obtained after stimulation of both eyes separately and the side of stimulation was changed after two averages. Visual acuity was improved postoperatively in eight cases. A significant VEP change occurred if latency prolongation of more than 50% was seen. The changes of VEPs were so profound [complete potential loss occurred in ten cases]