Fig. 1

Study design. a Concentration-response curve for magnesium. Magnesium doses were added every 10 min to the buffer solution until the suppression of single twitch force amplitude was achieved. b Concentration-response curve for rocuronium. Rocuronium boluses were added every 15 min until the suppression of single twitch force amplitude was achieved. To assess the effect of magnesium, the experiment was repeated with a magnesium bolus given 10 min prior to commencing rocuronium dosing. c Concentration-response curve for sugammadex. After an initial bolus of rocuronium which caused at least 90% suppression of single twitch force amplitude, sugammadex doses were given every 10 min until full recovery of single twitch force amplitude was achieved. To assess the effect of magnesium given before neuromuscular block, the experiment was repeated with a magnesium bolus given 10 min prior to administering the rocuronium dose. To assess the effect of magnesium given after the establishment of neuromuscular block, the experiment was repeated with a magnesium bolus given after partial reversal with sugammadex and then sugammadex dosing was continued. d Effect of magnesium on the safety margin of reversal. An initial rocuronium dose was followed by incremental doses of sugammadex to achieve either a “full” or clinically “accepted” reversal, as measured by the train-of-four (TOF) ratio. Magnesium was given in increments and the TOF ratio reassessed after every change in magnesium concentration. Mg: magnesium, Roc: rocuronium, Sug: sugammadex, TOF: measurement of train-of-four ratio