Background and Goal of Study: Perioperative magnesium sulphate(MgSO4) use for analgesic, antiarrhythmic and obstetric purpose. The effects of increased MgSO4 in clinical practice on rocuronium induced neuromuscular block and sugammadex reversal is not clearly quantified. This studies were investigated the effect of MgSO4 on neuromuscular blockade of rocuronium and sugammadex reversal in the isolated phrenic nerve-hemidiaphragm preparation of rats.
Materials and methods: Rat phrenic nerve-hemidiaphragm preparations were isolated and randomly allocated 4 groups by MgSO4 concentration [1mM, 2mM, 3mM, 4mM, N=10 in each group] in Krebs solution. TOFR and twitch height response were recorded mechanomyograhycally. The preparations were blocked by incremental dose of rocuronium(initial 200 µg + booster 100 µg in 75 ml bath) and dose-response curve with EC5, EC50, EC90, EC95 of rocuronium in each group were calculated using a logistic model.For reversal, we used equimolar dose of sugammadex to administered rocuronium. Recovery index, time to maximal twitch height and TOFR> 0.9 after sugammadex reversal was obtained.
Results and discussion: EC5 of rocuronium didn't show difference in 4 groups. EC50, EC90, EC95 of rocuronium were reduced significantly by the increased as MgSO4 concentration. However, EC50, EC90, EC95 of rocuronium were not different between 3mM and 4mM groups. Recovery index, time to maximal twitch height and TOF> 0.9 after sugammadex infusion was not different in all 4 groups.
Conclusion(s): Increase of MgSO4 concentration (1mM to 3mM) enhances rocuronium iduced neuromuscular block in rats' hemidiaphragm preparations. Increase of MgSO4 concentration does not reduce reversal effect of equimolar dose of sugammadex to rocuronium in rats' hemidiaphragm preparation.
References: Bom A, Hope F, Rutherford S, Thomson K: Preclinical pharmacology of sugammadex. J Crit Care 2009; 24:29-35.

Effects of MgSO4 on neuromuscular blockade of rocuronium and sugammadex reversal in the isolated phrenic nerve-hemidiaphragm preparation of rats