Differential effects of propofol and nitrous oxide on posterior tibial nerve somatosensory cortical evoked potentials during alfentanil anaesthesia
Kalkman, C.J.; Traast, H.; Zuurmond, W.W.; Bovill, J.G.
British Journal of Anaesthesia 66(4): 483-489
1991
ISSN/ISBN: 0007-0912 PMID: 2025476 Document Number: 373729
We have studied differential effects of propofol and nitrous oxide on posterior tibial nerve somatosensory evoked potentials (PTN-SEP) during a continuous infusion of alfentanil. In study 1,14 patients received initially 66% nitrous oxide in oxygen, which was replaced 90 min after incision by propofol 6 mg kg-1 h-1. This substitution resulted in a significant increase in mean P1N1 amplitude from 1.01 (SD 1.14) .mu.V to 2.61 (2.17) .mu.V (P < 0.01), while amplitude of later peaks were unaffected. Latencies of peaks N1, P2 and N2 increased after the substitution. In study 2, 30 patients undergoing spinal surgery received either alfentanil-nitrous oxide anesthesia (group 1, n = 15) or alfentanil-propofol anesthesia (group II, n = 15). P1N1 amplitude was significantly greater in group II (3.24 (1.08) .mu.V) than in group I (1.64 (0.97) .mu.V) (P < 0.01). Latencies of peaks P2 and N2 were of significantly greater duration in group II than in group I. Because early cortical PTN-SEP peaks were preserved better during alfentanil-propofol anaesthesia we conclude that this combination may be a suitable alternative to alfentanil-nitrous oxide anaesthesia, when spinal cord function monitoring with PTN-SEP is indicated.