Comparison of neuromuscular blockade in upper facial and hypothenar muscles

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Abstract
Facial and hand muscles are used frequently for monitoring neuromuscular blockade. Therefore, we compared changes in electrically evoked muscle potential magnitude in upper facial and hypothenar muscles after fixed doses of neuromuscular blockers (succinylcholine, 750 µg/kg; pancuronium, 70 µg/kg; vecuronium, 50 µg/kg; and atracurium, 300 µg/kg). Face-hand comparisons were made in both anesthetized (nitrous oxide/narcotic, n=51) and comatose (closed-head injuries, n=5) patients. In 24 anesthetized patients, complete blockade of the hypothenar muscles prevented quantitative comparison. In the remaining 27 patients, the relaxant effect (as determined by the percentage change from prerelaxant baseline muscle potentials) was significantly smaller (PP0.05) of comatose patients was smaller and more variable than that seen during anesthesia. These results illustrate the valuc of quantitative monitoring of neuromuscular function, especially during highly variable and unpredictable drug-induced blockade in the comatose state. We conclude that during narcotic-based anesthesia the upper facial and hand muscles are differentially sensitive to commonly used neuromuscular blockers.