[Potentiation by nitrous oxide of vecuronium neuromuscular blockade measured by EMG]

This study was designed to evaluate the potentiation by nitrous oxide of the neuromuscular blockade by vecuronium measured by the evoked electromyogram (EMG). Vecuronium, 0.0225, 0.03 or 0.04 mg.kg-1 was given during thiamylalfentanyl anesthesia with and without nitrous oxide, and EMG of the hypothenar muscle was measured. ED50 and ED95 were 0.0271 and 0.0480 mg.kg-1 in the group receiving nitrous oxide, and 0.0304 and 0.0555 mg.kg-1 in the group not receiving nitrous oxide. Dose-response curve (DRC) constructed from log-probit transformation for the group not receiving nitrous oxide was shifted to the right by 12.4%. By multiple regression analysis it was also revealed that the magnitude of the blockade was influenced by dose, nitrous oxide, sex and body mass index (BMI). DRCs for the female patients were shifted to the left, and the those differences caused by sex were shown to increase during anesthesia without nitrous oxide. It is concluded that the potentiation by nitrous oxide of vecuronium neuromuscular blockade obtained by EMG is less than that reported measuring by mechanomyogram, and also the magnitude of the blockade is influenced by sex and BMI, but the difference caused by sex is decreased by administration of nitrous oxide.