Cardiovascular effects of magnesium sulphate in the baboon.

The effect of Mg infusions on cardiovascular function were investigated in 6 adult male chacma baboons over a wide range of serum Mg concentrations. There was a dose-dependent reduction in systemic vascular resistance which correlated well with serum Mg levels (r = -0.67; p less than 0.001), but arterial blood pressure was only moderately affected at serum Mg levels below 5 mmol/l. Heart rate was reduced at serum Mg concentrations above 5 mmol/l. Cardiac output and stroke work were increased at all Mg levels up to 5 mmol/l, and stroke volume increased significantly until the serum Mg level exceeded 7 mmol/l. Central venous pressure and pulmonary capillary wedge pressure were not affected by increasing magnesium levels, and there was no evidence of myocardial depression at any level of serum Mg.