Magnesium-induced recurarisation after reversal of rocuronium-induced neuromuscular block with sugammadex

A 61-year-old woman (57kg, 171cm) underwent surgery under general anaesthesia with desflurane 5.8-6.1 vol. % end-tidal, remifentanil 0.2-0.4g/kg/min and rocuronium 35mg (0.61mg/kg). On return of the second twitch in the train-of-four (TOF) stimulation measured by acceleromyography, sugammadex 120mg (2.1mg/kg) was given. After complete neuromuscular recovery, magnesium sulphate 3600mg (60mg/kg) was injected intravenously over 5min to treat atrial fibrillation. This was associated with recurarisation with a nadir [first twitch=25%, TOF ratio (TOFR)=67%] 7min after the start of the magnesium sulphate infusion (magnesium plasma level: 2.67mM). A spontaneous twitch value and a TOFR of >90% were observed 45min after the beginning of the magnesium sulphate infusion under general anaesthesia. Rapid infusion of magnesium sulphate may re-establish a sugammadex-reversed, rocuronium-induced neuromuscular block during general anaesthesia, probably because of the high plasma level of magnesium (2.67mM). Desflurane and a small fraction of unbound rocuronium may amplify the known muscle relaxing effects of magnesium. Intravenous injection of magnesium sulphate is not recommended in patients after general anaesthesia with neuromuscular relaxants, particularly after sugammadex reversal. Quantitative neuromuscular monitoring should be used for reversing aminosteroid muscle relaxants with sugammadex - particularly in combination with magnesium injection - to prevent post-operative residual curarisation.