Intraoperative monitoring of tibialis anterior muscle motor evoked responses to transcranial electrical stimulation during partial neuromuscular blockade
Kalkman, C.J.; Drummond, J.C.; Kennelly, N.A.; Patel, P.M.; Partridge, B.L.
Anesthesia and Analgesia 75(4): 584-589
1992
ISSN/ISBN: 0003-2999 PMID: 1356320 Document Number: 400298
We studied the feasibility of recording motor evoked responses to transcranial electrical stimulation (tce-MERs) during partial neuromuscular blockade (NMB). In 11 patients, compound muscle action potentials were recorded from the tibialis anterior muscle in response to transcranial electrical stimulation during various levels of vercuronium-induced NMB. The level of NMB was assessed by accelerometry of the adductor pollicis muscle after train-of-four stimulation of the ulnar nerve. The compound muscle action potential was also recorded from the tibialis anterior muscle after direct stimulation of the peroneal nerve (M-response) as an alternative means of assessing the degree of NMB. In all patients, tce-MERs could be recorded reliably during anesthesia with N2O and an continuous infusion of sufentanil (0.5 .mu.g .cntdot. kg-1 .cntdot. h-1). An intact train-of-four was present in all patients, and the amplitude of the first twitch was recorded and designated as the control value. Before administration of vercuronium, the M-response amplitude was 9.6 .+-. 3.6 (mean .+-. SD) mV, and the tce-MER amplitude was 1.21 .+-. 0.66 mV. Although administration of vecuronium (0.05 mg/kg) resulted in loss of the mechanical adductor pollicis response to 8 of the 11 patients, the M-response and the tce-MER remained recordable. Subsequently, during and infusion of vercuronium, adjusted to maintain one or two mechanical responses to train-of-four stimulation, the average M-response to peroneal nerve stimulation was 5.2 .+-. 2.5 mV (53% of the control value) and tce-MER amplitude was 0.59 .+-. 0.36 mV (59 % of the control value). During incomplete relaxation, there was good corelation between the amplitude of the M-response and the of the tce-MER (r = 0.85; P < 0.01). the ratio of tce-MER amplitude to M-response amplitude to M-response amplitude remained constant, suggesting that it may be feasible to use the amplitude of the M-response to "calibrate" the tce-MER amplitude during vercuronium administration. The data indicate that tce-MER monitoring is feasible during clinically effective levels of NMB.