EFFECT OF VECURONIUM-INDUCED NEUROMUSCULAR BLOCKADE ON CORTICAL MOTOREVOKED-POTENTIALS

Authors
Citation
Tb. Sloan et R. Erian, EFFECT OF VECURONIUM-INDUCED NEUROMUSCULAR BLOCKADE ON CORTICAL MOTOREVOKED-POTENTIALS, Anesthesiology, 78(5), 1993, pp. 966-973
Citations number
26
Categorie Soggetti
Anesthesiology
Journal title
ISSN journal
00033022
Volume
78
Issue
5
Year of publication
1993
Pages
966 - 973
Database
ISI
SICI code
0003-3022(1993)78:5<966:EOVNBO>2.0.ZU;2-R
Abstract
Background. Neuromuscular blockade (NMB) is a frequent component of an esthetic techniques used during surgery in which monitoring of the ner vous system is desirable. Because NMB should affect the evoked muscle response to transcranial magnetic stimulation (tcMMEP), their relation ship in a primate model was characterized. Methods. Transcranial magne tic stimulation was characterized during NMB using an infusion of vecu ronium in ten adult cynomologous monkeys during anesthesia with a cont inuous ketamine infusion. Neuromuscular blockade was measured by peak- to-peak amplitude of the evoked muscular activity (compound muscle act ion potential [m-response]) of the thenar muscles and mechanical muscl e action (ratio of the fourth to first peak in the train of four [TOF] ) after direct stimulation of the median nerve. Neuromuscular blockade was increased incrementally to complete block and then allowed to dec rease until complete resolution of measurable block. Transcranial magn etic stimulation was assessed by measuring the onset latency (time fro m stimulation to beginning response) and amplitude of the thenar EMG r esponse. Cortical stimulation was accomplished using a Cadwell MES-10 magnetic stimulator at 80% of full output (1.6 Tesla). Results: The tc MMEP, m-response amplitude, and mechanical muscle action, unblocked, w ere reduced with increasing NMB. Transcranial magnetic stimulation amp litude was more variable than was onset latency. Transcranial magnetic stimulation amplitude reduction from the baseline value did not achie ve statistical significance until the m-response amplitude was reduced to 0.2 of baseline or until the TOF ratio was reduced to 0.1. Transcr anial magnetic stimulation onset latency prolongation from baseline wa s not significantly affected by declining TOF ratios, but was prolonge d when the m-response declined to 0.1 of baseline. Conclusions: This s tudy indicates that tcMMEP onset latency is not significantly affected by NMB if the degree of blockade in the muscles used for tcMMEP monit oring is not extreme (greater than 0.2 of baseline by m-response ampli tude or a TOF ratio of 0.1 or greater). If monitoring of tcMMEP amplit ude is desired, partial neuromuscular blockade may be acceptable. Howe ver, amplitude reduction may occur during partial NMB. Maintenance of a constant degree of NMB is suggested to minimize amplitude fluctuatio ns.