Post-Ischemic Helium Provides Neuroprotection in Rats Subjected to Middle Cerebral Artery Occlusion-Induced Ischemia by Producing Hypothermia

During the past decade, studies on the manipulation of various inhaled inert gases during ischemia and/or reperfusion have led to the conclusion that inert gases may be promising agents for treating acute ischemic stroke and perinatal hypoxia-ischemia insults. Although there is a general consensus that among these gases xenon is a golden standard, the possible widespread clinical use of xenon experiences major obstacles, namely its availability and cost of production. Interestingly, recent findings have shown that helium, which is a cost-efficient inert gas with no anesthetic properties, can provide neuroprotection against acute ischemic stroke in vivo when administered during ischemia and early reperfusion. We have investigated whether helium provides neuroprotection in rats subjected to middle cerebral artery occlusion (MCAO) when administered after reperfusion, a condition prerequisite for the therapeutic viability and possible clinical use of helium. In this study, we show that helium at 75 vol% produces neuroprotection and improvement of neurologic outcome in rats subjected to transient MCAO by producing hypothermia on account of its high specific heat as compared with air.