Objective: To evaluate the hypothesis that magnesium sulphate (SO4Mg), usually administered for protecting the myocardium and decreasing the rate of arrhythmias in cardiac surgery, was able to control the hypertensive peaks occurring during cardiopulmonary bypass (CPB), as efficiently as nicardipine (N).
Study design: Randomized controlled trial.
Patients: Forty patients were allocated into two groups when hypertensive peaks occurred during CPB. The patients of the N group were then given nicardipine 0.016 mg.kg-1 and those of the SO4Mg group received magnesium sulphate 50 mg.kg-1.
Methods: Anaesthesia technique was identical and during normothermic CPB the flow remained constant at 2.4 L.min-1, during the 10 min following N or SO4Mg administration. The usual haemodynamic variables were monitored.
Results: Both N and SO4Mg decreased significantly the MAP and the SVR over the 9 min following their administration. The decrease was more marked after SO4Mg. As the flow of the pump was unchanged after their injection the decrease can be attributed to the relaxing effect of these agents on the smooth vascular muscles.
Conclusions: SO4Mg permits to treat hypertensive peaks occurring during CPB as efficiently as N. Three grammes of SO4Mg have an hypotensive effect equivalent to that of 1 mg of nicardipine. However repetitive injections of SO4Mg cannot be recommended because of the risk for hypermagnesemia.