Abstract
Introduction: Magnesium inhibits acetylcholine release from the presynaptic membrane at the motor end plate; and thus it enhances the effect of non-depolarising muscle relaxants. Priming technique shortens the time of onset of non depolarising neuromuscular relaxants. Thus, the combination of magnesium pre-treatment and priming may be an effective method for achieving an early tracheal intubating condition. We studied the effect of magnesium sulphate pretreatment in combination with atracurium priming on onset and duration of neuromuscular blockade, compared with these methods when used alone.
 Materials and Methods: 100 patients scheduled for elective surgical procedures under general anaesthesia were divided into 4 groups. Group A (n=25) recieved priming with 0.05 mg/kg atracurium, three minutes before the intubating dose of atracurium 0.5 mg/kg, group M (n=25) was given 50 mg/kg magnesium sulphate as infusion over 10 mins before intubating dose of atracurium, group MA (n=25) received both the magnesium sulphate pretreatment and the priming dose of atracurium. Group N (n = 25) were given 0.5mg/kg atracurium alone as part of general anaesthesia. Tracheal intubation was done when the TOF stimulation showed single twitch which was measured at intervals of every 30 seconds. Parameters studied were the time to onset of neuromuscular blockade and the duration of neuromuscular blockade.
 Results: The MA group had the shortest onset time (mean±SD) 114.30±20.19 sec (p < 0.001) compared to the other groups. The duration of blockade was prolonged in both Group MA and Group M compared to other groups (P<0.001). Few adverse effects were reported in groups receiving magnesium, but were clinically not significant.
 Conclusion: Magnesium sulphate pretreatment in combination with atracurium priming shortens the time of onset of neuromuscular blockade when compared to magnesium sulphate pretreatment or priming used alone.
 Keywords: Atracurium priming, magnesium sulphate, neuromuscular blockade
Highlights
Introduction: Magnesium inhibits acetylcholine release from the presynaptic membrane at the motor end plate; and it enhances the effect of non-depolarising muscle relaxants
We studied the effect of magnesium sulphate pretreatment in combination with atracurium priming on onset and duration of neuromuscular blockade, compared with these methods when used alone
Magnesium sulphate pretreatment in combination with atracurium priming shortens the time of onset of neuromuscular blockade when compared to magnesium sulphate pretreatment or priming used alone
Summary
Magnesium inhibits acetylcholine release from the presynaptic membrane at the motor end plate; and it enhances the effect of non-depolarising muscle relaxants. Priming technique shortens the time of onset of non depolarising neuromuscular relaxants. We studied the effect of magnesium sulphate pretreatment in combination with atracurium priming on onset and duration of neuromuscular blockade, compared with these methods when used alone. Conclusion: Magnesium sulphate pretreatment in combination with atracurium priming shortens the time of onset of neuromuscular blockade when compared to magnesium sulphate pretreatment or priming used alone. Magnesium has been found to shorten the onset time of non-depolarising muscle relaxants and potentiates their effect.[3,4]. It is hypothesized that this approach will shorten the time of onset of non depolarising neuromuscular relaxant drugs 5,6. The administration of the second larger dose at the time of the development of the maximal effect of the priming dose increasesthe receptor occupancy to over 90% which is required for profound neuromuscular blockade[5]
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