A recent controlled trial by Temkin et al has demonstrated that prolonged levels of IV magnesium do not improve the outcomes of patients suffering from traumatic brain injury (TBI) (Temkin et al, Lancet Neurology 2007; 6: 29-38). The context here is that numerous animal studies have shown that magnesium delivered at high levels (intravenously, intracranially) can have “neuroprotective” effects in the setting of stroke, brain injury, or excessive bleeding. Unfortunately, these positive results have not been translated into benefits for patients. To learn more, see our recent review article here, or a quick, general introduction to neuroprotection here.
Here’s what the study examined: approx 500 patients, who had suffered TBI, were assigned to either receive placebo or one of 2 doses of magnesium, within 8 hours of injury, and then ongoing for 5 days. The magnesium doses were designed so that each patient ended up having about the same blood level of magnesium. The primary outcome followed was the patient’s rating on a clinical outcome scale. This scale combines outcomes such as mortality, the occurrence of seizures, functional deficits, and performance on neuropsychological tests, into a single number.
What they found: the higher dose of magnesium did not significantly affect patients’ clinical outcome (as measured by the composite score), but the lower magnesium dose showed a statistically significant negative effect. In other words, at best magnesium showed a benefit, and at worst, could make a patient’s condition worse.
This work builds on our report from 2005, in which we examined whether magnesium can even reach the brain when delivered intravenously. We found that prolonged infusions produced only minimal increases (11-15%) in magnesium in the brain. (McKee et al, Critical Care Medicine, 2005 Mar;33(3):661-6). Our work did not extend these results to whether such a small increase could or could not affect the clinical outcome of patients. This is where the Temkin study comes in. (Also, without getting into too many details, their group studied patients with brain injury, whereas our study examined patients who primarily suffered from a type of bleeding in the brain, called subarachnoid hemorrhage or SAH).
Another series of studies, the most important of which is the IMAGES trial, have examined the impact of magnesium for patients suffering from stroke. Stay tuned for a future post where I’ll dive into that trial and its follow-on’s in more detail…