Effects of pretreatment with magnesium on muscle relaxation and cardiovascular responses in tracheal intubation using the priming principle for vecuronium

Abstract

In addition to its direct effects on blood vessels, the myocardium, and neuromuscular junctions, magnesium can act as an adrenergic antagonist and can inhibit the release of catecholamines both from adrenergic nerve terminals and from the adrenal medulla. This study was undertaken to evaluate these effects of magnesium on muscle relaxation and cardiovascular response during tracheal intubation. Forty ASA I or II patients undergoing elective surgery were allocated to a magnesium or a control group. Three minutes after priming with vecuronium 0.015 mg·kg^-1, the magnesium group received vecuronium 0.085 mg·kg^-1 and magnesium sulfate 40 mg·kg^-1, while the control group received an equivalent volume of vecuronium and saline. The percent change from baseline in mean arterial pressure after tracheal intubation was significantly smaller (P<0.01) in the magnesium group than in the control group, but the percent change in heart rate was similar. There were no significant changes in plasma catecholamine concentrations after tracheal intubation in either group. The onset time of vecuronium was significantly shorter in the magnesium group than in the control group. The duration of action of vecuronium was significantly longer in the magnesium group than in the control group. Serum magnesium concentrations at 90 min after its administration were significantly higher than baseline. We concluded that vecuronium priming with magnesium pretreatment inhibits the hypertension associated with tracheal intubation and shortens the onset time of vecuronium, but prolongs it duration of action.

Keywords: Magnesium; Priming principle; Vecuronium.