COMPARATIVE VASCULAR EFFECTS OF MAGNESIUM -SULFATE AND NICARDIPINE DURING CARDIOPULMONARY BYPASS

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 hyper tensive peaks occurring during cardiopulmonary bypass (CPB), as effici ently as nicardipine (N). Study design: Randomized controlled trial. P atients: Forty patients were allocated into two groups when hypertensi ve peaks occurred during CPB. The patients of the N group were then gi ven nicardipine 0.016 mg . kg(-1) and those of the SO4Mg group receive d magnesium sulphate 50 mg . kg(-1). Methods: Anaesthesia technique wa s identical and during normothermic CPB the now 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 follo wing their administration. The decrease was more marked after SO4Mg. A s the now of the pump was unchanged after their injection the decrease can be attributed to the relaxing effect of these agents on the smoot h vascular muscles. Conclusions: SO4Mg permits to treat hypertensive p eaks 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 o f the risk for hypermagnesemia.