EFFECTS OF MAGNESIUM-SULFATE ON ELECTRICAL VENTRICULAR DEFIBRILLATIONOF DOGS

Magnesium ion infusion has been reported for treatment of hypo magnese mia often associated with myocardial infarction and with surgeries inv olving cardiopulmonary bypass (CPB). Magnesium infusion before CPB has been reported to adversely affect the ability to defibrillate after C PB. However, there are also reports of magnesium ion infusion facilita ting defibrillation of refractory ventricular fibrillation. This study evaluated the isolated effect of magnesium ion infusion on the shock intensity requirements for electrical defibrillation. The electric cur rent required to defibrillate with 50% success (the ED50) was estimate d in five mongrel dogs at baseline and again after each of four magnes ium sulfate (80 mg/kg) infusions. The total serum magnesium level incr eased from 2.32 +/- 0.08 mg/dL (mean +/- SD) to 7.92 +/- 0.80 mg/dL. T he mean estimated ED50 decreased from 12.8 +/- 2.9 A at baseline, to 1 1.1 +/- 0.8 A after the fourth infusion (P < .05), decreasing the deli vered energy by 25%. Magnesium sulfate infusion was associated with a significant decrease in the electrical requirements for defibrillation .