Randomized Double Blind Controlled Study Comparing Vecuronium Priming, Magnesium Pretreatment and Combination of the Two Methods on the Onset of Intubating Conditions

Introduction: Priming markedly shortens the onset time to non depolarising neuromuscular blocking drugs. Magnesium inhibits presynaptic acetylcholine release at the motor end plate; hence magnesium potentiates the effect of non-depolarising muscle relaxants and shortens their onset time. Thus, the combination of priming and magnesium pre-treatment may be an alternative, effective method for accomplishing early tracheal intubation. We investigated whether magnesium sulphate with vecuronium priming shortens the onset of neuromuscular blockade, compared with these methods used alone. Materials and Methods: 100 patients undergoing elective surgical procedures under general anaesthesia were randomized into group N (n = 25) were given 0.1mg/kg vecuronium, group V (n=25) were primed with 0.01 mg/kg vecuronium three minutes before a further dose of 0.09 mg/kg vecuronium, group M (n=25) were given an infusion of 50 mg/kg magnesium sulphate before vecuronium, group MV (n=25) were given both the magnesium sulphate and the priming dose of vecuronium. Trachea was intubated when the TOF stimulus showed only one twitch measured at intervals of 30 seconds. The time to onset of neuromuscular blockade, duration of blockade and tracheal intubating conditions were measured. Results: The magnesium and prime group had the shortest mean (SD) onset time 112.80 (19.89) sec (p < 0.001) compared to the other groups. The duration of blockade was prolonged in both Group M and Group MV (P < 0.001). Few adverse effects were reported in magnesium preloaded group, clinically not significant. Conclusion: The combination of magnesium sulphate and vecuronium priming accelerated the onset of neuromuscular blockade compared with either magnesium sulphate or priming used alone.