Severe cerebral desaturation during shoulder arthroscopy in the beach-chair position.

During shoulder arthroscopy in the beach-chair position, cerebral ischemia may be a serious complication because prolonged hypotension may affect regional cerebral oxygen supply. We present the cases of 2 patients in whom a reduction in mean arterial pressure after anesthesia provoked a decrease in frontal lobe oxygenation to below the level that causes presyncopal symptoms in the awake subject. In the healthy middle-aged patient, cerebral oxygenation decreased by approximately 40%, indicating that cerebral blood flow was markedly reduced, and intravenous administration of ephedrine rapidly restored cerebral oxygenation. During surgery in the beach-chair position, hypotension must be avoided, and in all patients regional, cerebral oxygenation should be monitored and optimized.