Magnesium sulfate accelerates the onset of low-dose rocuronium in patients undergoing laryngeal microsurgery

We evaluated the effect of magnesium sulfate-an enhancer of neuromuscular blockade-on onset and duration of low dose of rocuronium, and on operating conditions during laryngeal microsurgery.

Randomized, prospective, double-blinded study.

Eighty-four patients scheduled for elective laryngeal microsurgery.

Patients were randomly allocated to receive different doses of rocuronium: 0.6 mg/kg (group C, n=28), 0.45 mg/kg (group LR, n=28), or 0.45 mg/kg plus magnesium sulfate 30 mg/kg (group LM, n=28).

We measured the onset time and duration of action of rocuronium, and evaluated the surgeon's satisfaction with the operating conditions.

Group LR showed significantly delayed onset time (group C: 87±22 seconds, group LR: 127±47 seconds, and group LM: 89±32 seconds; P=.001) and maximal suppression than did other groups (group C: 102±30 seconds, group LR: 155±66 seconds, and group LM: 105±36 seconds; P=.002). Duration of action of rocuronium was significantly longer in group C than in other groups (group C: 39±7 minutes, group LR: 28±8 minutes, group LRM: 31±8 minutes; P<.001). Laryngoscope placement score (P=.002), surgeon's satisfaction (P=.005), and sore throat (P=.035) were significantly worse in group LR.

Magnesium sulfate 30 mg/kg accelerated the onset and improved operating conditions of low-dose rocuronium without prolongation of action.