A randomised controlled trial comparing rocuronium priming, magnesium pre-treatment and a combination of the two...

We investigated whether magnesium sulphate combined with rocuronium priming shortens the onset of neuromuscular blockade, compared with these methods used alone. Ninety-two patients scheduled for general anaesthesia were randomly allocated to one of four groups: controls were given 0.6 mg.kg(-1) rocuronium; patients in the prime group were given 0.06 mg.kg(-1) rocuronium three minutes before a further dose of 0.54 mg.kg(-1) rocuronium; patients in the magnesium group were given an infusion of 50 mg.kg(-1) magnesium sulphate before rocuronium and patients in the magnesium and prime group were given both the magnesium sulphate and the priming dose of rocuronium. Tracheal intubation was attempted 40 s after the rocuronium injection. The time to onset of neuromuscular blockade was the primary outcome; duration of blockade and tracheal intubating conditions were also measured. The group allocation and study drugs were coded and concealed until statistical analyses were completed. The magnesium and prime group had the shortest mean (SD) onset time (55 (16)s; p < 0.001), and best tracheal intubating conditions (p < 0.05). No statistical difference was found for the duration of blockade. As for adverse events, a burning or heat sensation was reported in eight (35%) and six (26%) patients in the magnesium and magnesium and prime groups, respectively. The combination of magnesium sulphate and rocuronium priming accelerated the onset or neuromuscular blockade and improved rapid-sequence intubating conditions, compared with either magnesium sulphate or priming used alone.