British Journal of Anaesthesia, Vol 78, Issue 6 701-706, Copyright © 1997 by The Board of Management and Trustees of the British Journal of Anaesthesia
O. Langeron, F. Lille, O. Zerhouni, G. Orliaguet, G. Saillant, B. Riou and P. Coriat
Cortical somatosensory evoked potentials (CSEP) allow monitoring of spinal
cord function during surgery. Ketamine has been shown to enhance CSEP
amplitude, but there is no previous study comparing its effects with those
of other anaesthetic regimens. Therefore, we have compared the effects of
ketamine with those of fentanyl, both combined with midazolam, on CSEP
monitoring during major spine surgery. Twenty patients with normal
preoperative CSEP were allocated randomly to a ketamine or fentanyl group.
Anaesthesia was induced with ketamine 3 mg kg-1 or fentanyl 6 micrograms
kg-1 i.v., and midazolam 0.3 mg kg-1 i.v in both groups, and maintained
with continuous i.v infusion of ketamine 2 mg kg-1 h-1 or fentanyl 3
micrograms kg-1 h-1, combined in both groups with midazolam 0.15 mg kg-1
h-1 and 60% nitrous oxide in oxygen. CSEP were elicited by tibial posterior
nerve stimulation and measured P1 and N1 latencies, and P1-N1 amplitude,
CSEP were recorded before and after induction, at 15 min, 1 and 2 h after
induction, during skin closure and after removal of nitrous oxide. Both
groups were comparable in characteristics, duration of surgery, mean
arterial pressure and temperature. CSEP latencies were not significantly
affected in either group. CSEP amplitude decreased significantly over time
in the fentanyl group (from mean 2.02 (SEM 0.41) to 0.95 (0.17) microV, P
< 0.05), but not in the ketamine group (from 1.33 (0.36) to 1.05 (0.31)
microV, ns). Nevertheless, we did not observe any significant differences
in amplitudes or latencies between the two groups. The delay in obtaining
the first voluntary postoperative motor response was significantly greater
in the ketamine group (170 (54) vs 55 (17) min, P < 0.01). Both ketamine
and fentanyl allowed us to obtain reliable CSEP during major spine surgery,
and there were no significant difference between these two anaesthetic
regimens for CSEP monitoring, but a longer delay for voluntary
postoperative motor assessment was observed in the ketamine group.
CLINICAL INVESTIGATIONS
Comparison of the effects of ketamine-midazolam with those of fentanyl- midazolam on cortical somatosensory evoked potentials during major spine surgery
Department of Anaesthesiology and Critical Care, Hopital Pitie-Salpetriere, Paris VI University, Paris, France; Department of Neurophysiology, Hopital Pitie-Salpetriere, Paris VI University, Paris, France; Department of Orthopaedic Surgery, Hopital Pitie-Salpetriere, Paris VI University, Paris, France; Department of Anaesthesiology, Hôpital Necker, Paris, France
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