Effects of etidocaine administered epidurally on changes in somatosensory evoked potentials after dermatomal stimulation.

The effect of lumbar epidural anesthesia with similar volumes (approximately 20 ml) of 1% and 1.5% etidocaine on early (less than 0.5 seconds) somatosensory evoked potentials (SEPs) to electrical stimulation of the S1, L1, and T10 dermatomes was examined in two groups of ten patients in a randomized, double-blind study. Level of analgesia to pinprick was T7.7 +/- 0.9 in the 1% group and T6.6 +/- 0.6 in the 1.5% group and all patients had total motor block. Despite similar analgesia to pinprick, SEP amplitude was more reduced in the 1.5% group, in which SEPs were abolished in all patients at the L1 level.