Somatosensory-evoked potentials during block of surgical stimulation with propofol

The effect of propofol on somatosensory evoked potentials was assessed during different intra-operative stimuli in prolonged (greater than 2 h) abdominal operations. SSEP were used to evaluate the extent of block of sensory nerve conduction at the following stages: preinduction; during steady state anaesthesia; during traction of the mesentery; 10 min after anaesthesia. Propofol 100 micrograms kg-1 min-1 and nitrous oxide in oxygen anaesthesia induced a significant decrease in amplitude of the SSEP; noxious stimulation resulted in an increase in afferent nerve transmission and a concomitant increase of amplitude of the late evoked potential. After operation, impulse transmission recovered rapidly and the amplitude was similar to control at 10 min after anaesthesia.