The effect of heliox treatment in a rat model of focal transient cerebral ischemia.

Manipulation of inhaled gases during ischemia/reperfusion is a potential novel therapy for acute stroke. We previously found that treatment with a mixture of 70%/30% helium/oxygen (heliox) or 100% oxygen protects the brain against acute focal ischemia-reperfusion injury. This study evaluates the potential neuro-protective effects of delayed heliox treatment and its dose response effects in a rat transient focal cerebral ischemia model. Adult male rats were subjected to 2-h middle cerebral artery occlusion and then assigned to 1 of 4 inhaled gas exposure groups: I: 70%/30% nitrogen/oxygen (control); II: 70%/30% helium/oxygen administered immediately after occlusion; III: 70%/30% helium/oxygen administered after a 30-60 min delay; or, IV: 40%/30%/30% nitrogen/helium/oxygen administered immediately after occlusion. Outcome measurements included infarct size and neurological deficit score. Mean infarct sizes from groups I to IV were 228, 35, 109, and 124 mm³ respectively (p=0.012). Only group II had significantly smaller infarct size compared to the control group (p=0.008). In addition, only Group II had a significantly lower neurological deficit score at 24h post ischemia when compared to the control group (p<0.001). Since heliox reduced infarct size and improved neurological deficit scores if initiated immediately after onset of ischemia, it may be a useful adjuvant to other stroke therapies.