Effects of Magnesium Sulfate Infusion on Cerebral Perfusion in Patients After Aneurysmal SAH
A meta-analysis of current data suggests that magnesium sulfate infusion improves the outcome after aneurysmal subarachnoid hemorrhage through a reduction in delayed ischemic neurological deficit. Two multi-center randomized controlled trials are currentl
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Abstract Background A meta-analysis of current data suggests that magnesium sulfate infusion improves the outcome after aneurysmal subarachnoid hemorrhage through a reduction in delayed ischemic neurological deficit. Two multi-center randomized controlled trials are currently underway to investigate this hypothesis. The possible pharmacological basis of this hypothesis includes neuroprotection and vasodilatation. We aim to investigate the cerebral hemodynamic effects of magnesium sulfate infusion in aneurysmal subarachnoid hemorrhage patients. Method A total of 12 patients who had experienced aneurysmal subarachnoid hemorrhage were randomized to magnesium sulfate infusion (n = 6) or placebo infusion (n = 6) for 14 days. Each patient had two perfusion MRIs performed, one in the first week after subarachnoid hemorrhage and one in the second week after subarachnoid hemorrhage. Findings Age, sex, and Fisher CT grade were not different between the two groups. All but one patient were of WFNS Grade I to II on presentation. There was no increase in rCBV, rCBF and MTT between the two perfusion scans within the same group or between the two groups. Conclusion Magnesium sulfate infusion, in the dosage of current clinical trials, did not increase cerebral blood volume and cerebral blood flow, as postulated by dilation of small vessels and/or collateral pathways. Keywords Cerebral blood flow • cerebral blood volume • magnesium sulfate • subarachnoid hemorrhage
Introduction Delayed ischemic neurological deficits or clinical vasospasm remain a major cause for delayed neurological morbidity and mortality for patients with aneurysmal subarachnoid hemorrhage. With the goal of improving the outcome of patients with aneurysmal subarachnoid hemorrhage by alleviating the harmful effects of delayed ischemic neurological deficits, magnesium sulfate infusion has been tested in six randomized controlled pilot studies (3,4,6,9–11). Four of these studies were eligible for the following meta-analysis. One study was excluded due to lack of 3 to 6 month follow up data; another was excluded due to the unconventional omission of nimodipine in the treatment group (4,6). Using the random effects model, the pooled odds ratio for symptomatic vasospasm or delayed cerebral ischemia was, 0.620, 95% CI 0.389 to 0.987, statistically significant. Similarly, the pooled odds ratio for unfavorable outcome is 1.598, 95% CI 1.074 to 2.377, statistically significant. Two multi-center randomized controlled trials are currently underway to investigate the above hypothesis. In an experimental model of drug or SAH-induced vasospasm, magnesium blocked voltage-dependent calcium channels and antagonized the action on N-methyl-d-aspartate receptors in the brain, preventing glutamate release and decreasing calcium influx during ischemic injury. The angiographic antispasmotic effect was not certain at the dosage of the current clinical trials (2). It remains a possibility that the vasodilatory effect predominantly acted on microcirculation level. We aim to investig
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