Somatosensory evoked potentials (SEPs) stimulating tibial nerve were monitored in ll patients receiving isoflurane anesthesia during operation. We found that reproducible SEPs were obtained throughout the surgical procedure in 100% of the cases we monitored while using isflurane at concentrations of 0.5-1.1%

Our data demonstrated 3 major effects of isofurane on SEP:

(a) occasional obliteration of components of N1, N2, P2, and N3 latencies, but never of P1,

(b) slight and insignificant prolongation of the average latencies of the 5 components,

(c) a significant increase in average amplitude of first component (N1-P1) (p<0.05)

In summary, our results suggested that in many instances the use of isoflurane anesthesia could be administered safely and successfully during intraoperative SEP monitoring without much influence on SEP early potentials on tibial never stimulation