The neuroprotective effect of magnesium sulphate during iatrogenically-induced ventricular fibrillation.

Unlabelled: We studied the neuroprotective effect of magnesium sulphate (MgSO4) administered before ventricular fibrillation was induced for internal cardioverter defibrillator threshold testing, and continued during reperfusion.

Methods: With the intention of increasing serum magnesium (Mg) to >1.2 mmol/L, 15 patients received 16 mmol of MgSO4, IV, followed by 5 mmol over two hours. Fifteen patients received placebo. Serum neuron-specific enolase (NSE) was assessed, as well as pre- and postoperative neurocognitive function.

Results: NSE increased in all patients, reaching a peak at 24 hours. The target Mg level was maintained throughout surgery in only nine of the Mg patients, and mainly in those with low lean body mass (LBM). In these patients, increased Mg levels were related to altered NSE release (P<0.05). NSE increased when serum Mg dropped to <1.2 mmol/L, finally exceeding levels of inadequately or untreated patients. Neurocognitive function after surgery was similar between groups.

Conclusions: Insufficient dosing could account for our results, as NSE release could be inhibited by Mg >1.2 mmol/L. For neuroprotection, the Mg dosage should be adjusted according to LBM and infusion be extended to >2 hours.