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Indian Journal of Clinical Anaesthesia

Pretreatment of magnesium sulphate accelerates neuromuscular block as compared to vecuronium priming – A randomized trial

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Author Details: Nalini KB, Muralidhar Danappa Patel, Pandya Khushal

Volume : 4

Issue : 1

Online ISSN : 2394-4994

Print ISSN : 2394-4781

Article First Page : 46

Article End Page : 50


Background: Action of non depolarising neuromuscular relaxants can be potentiated by small dose of priming. Priming reduces the time of onset of muscle relaxants by binding and occupying the choline receptors. Whereas magnesium decreases the release of acetylcholine in the presynaptic junction at the neuromuscular junction, hastening the effect of non-depolarising muscle relaxants. So we investigated whether pre- administration of magnesium reduces the time of onset of neuromuscular blockade compared to priming with vecuronium.
Method: 120 patients posted for surgery under general anaesthesia were recruited for this study. They were randomly allocated to control (group N), vecuronium priming (group P) or magnesium (group M) group. Group N (n = 40) received 100mcg/kg vecuronium after saline infusion, group P (n=40) received 10 mcg/kg vecuronium followed by 90 mcg/kg vecuronium. In group M (n=40) patients were infused with 40 mg/kg magnesium sulphate followed by 100 mcg/kg vecuronium. At the interval of 20 seconds, the train-of-four (TOF) responses to stimuli were recorded. Endotracheal intubation was done when one twitch was seen on the TOF stimulus. Time taken to intubation from the vecuronium intubating dose, time for reappearance of the 4th twitch, tracheal intubating conditions and side effects were noted.
Results: Onset time for intubation was significantly shortest in the group M as compared to other groups with mean time of 126.4 ± 23.3 seconds (p < 0.01). The reappearance of the 4th twitch was significantly prolonged in Group M as compared to other groups. The mean time for reappearance of 4th twitch was 77.5±10.4 minutes (p < 0.01) in group M. In the magnesium preloaded group, few patients had adverse events which was clinically not significant.
Conclusion: We conclude that pretreatment of magnesium infusion accelerates the onset of action of neuromuscular blockers and prolongs their duration of action.

Magnesium infusion, Onset of neuromuscular blockade, Priming, Intubation