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Published on: May 10, 2020
Influence of magnesium ion on human ventricular defibrillation after aortocoronary bypass surgery
Insights
Magnesium (Mg++) administration may not aid defibrillation after bypass surgery. High intraoperative magnesium levels (Mg++) exceeding 2.26 mg/dl may increase defibrillation shocks and energy needs.
Area of Science:
- Cardiology
- Anesthesiology
- Pharmacology
Background:
- Magnesium ion (Mg++) administration is known to aid defibrillation and reduce arrhythmias post-cardiopulmonary bypass.
- Its role in coronary artery bypass grafting (CABG) requires further investigation.
Purpose of the Study:
- To investigate the effect of magnesium ion (Mg++) administration on defibrillation and arrhythmias in patients undergoing coronary artery bypass grafting (CABG).
Main Methods:
- A prospective study involving 76 patients undergoing CABG.
- Patients were randomized to receive no Mg++, 0.25 mEq/kg Mg++ during bypass, or 0.375 mEq/kg Mg++ before bypass.
- Cardiac rhythm, defibrillation success, and energy requirements were monitored.
Main Results:
- Mg++ administration did not significantly affect spontaneous cardiac rhythm resumption or defibrillation.
- Increased shocks for defibrillation and higher energy requirements were observed in patients receiving Mg++ before bypass.
- Elevated plasma Mg++ levels (>2.26 mg/dl) correlated with greater defibrillation energy needs.
Conclusions:
- Intraoperative Mg++ administration may have adverse effects on cardiac defibrillation if plasma levels exceed 2.26 mg/dl.
- Careful monitoring of Mg++ levels is recommended during CABG to avoid potential negative impacts on defibrillation.
Abstract:
The administration of magnesium ion (Mg++) has been reported to defibrillate the ventricles and to decrease the incidence of arrhythmias after cardiopulmonary bypass. In a prospective study of 76 randomly selected patients undergoing coronary artery bypass grafting, patients received either no Mg++, 0.25 mEq/kg of Mg++ during cardiopulmonary bypass with the aorta clamped, or 0.375 mEq/kg of Mg++ before cardiopulmonary bypass. Spontaneous resumption of a cardiac rhythm or spontaneous defibrillation during reperfusion was not significantly affected by Mg++ administration. However, the number of shocks to initial and to sustained defibrillation and the energy required for the last direct-current shock was greatest in patients who received Mg++ before bypass and in those whose plasma Mg++ was greater than 2.26 mg/dl. Thus, the administration of Mg++ may have adverse effects on the heart if intraoperative plasma Mg++ exceeds 2.26 mg/dl.
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