Abstract
EEG, auditory middle latency evoked response (MLR) and somatosensory evoked poten-tial (SEP) were recorded in 10 patients undergoing hip or knee surgery during general anesthesia with propofol and/or N2O with epidural block. The analyses were made upen administration of 5mg/kg/hr of propofol+O2 (P 5mg), 5mg/kg/hr of propofol+N2O (P 5mg+N2O), and 10mg/kg/hr of propofol+O2 (P 10mg) and after extubation. The mean frequency of EEG decreased as infusion rate with propofol increased with no significant difference between administration with P 5mg and P 5mg+N2O. The amplitude of MLR decreased and the peak latency prolonged as propofol infusion rate increased. The ampli-tude of SEP N2O significantly decreased during P 5mg+N2O compared with P 5mg, P 10mg and after extubation. Propofol suppressed EEG and MLR waves, but not SEP N2O waves. N2O suppressed the amplitude of SEP N2O, but not EEG and MLR waves.
