Marked reduction in bispectral index with severe bradycardia without hypotension in a diabetic patient undergoing ophthalmic surgery.

A 75-year-old female patient underwent right vitrectomy under total intravenous anesthesia with propofol, ketamine and fentanyl. During the surgery sudden severe bradycardia (heart rate, 33 beats per min), without hypotension, occurred, which was relatively atropine-insensitive. This event was accompanied by a marked decrease in the bispectral index (BIS), from 70 to 40, and an elevation in the suppression ratio (33). Following the initiation of an isoproterenol infusion, the BIS promptly returned to 70, along with an increase in the heart rate. At the end of surgery the patient emerged from anesthesia without neurological sequelae. Severe bradycardia during anesthesia will cause cerebral hypoperfusion and this may affect cerebral function. We conclude that a BIS monitor may be a useful tool for the detection of bradycardia-related cerebral hypoperfusion.