The effect of hypoxemic reperfusion on cerebral protection after a severe global ischemic brain insult

Background and purpose: Reactive oxygen species contribute to membrane lipid peroxidation and neuronal death and have been implicated in anoxic encephalopathy. We tested whether hypoxemic reperfusion (HR) after global cerebral ischemia would improve neurological recovery. Methods: Two groups of pigs (n=11 in each group) were subjected to a model of a 10-min global cerebral and systemic ischemia to compare the effect of hypoxemic reperfusion (group HR) with the classical hyperoxemic control (group C). A third group not subjected to ischemia served as control to the control group (n=6, group CC), but received hyperoxygenation at the respective period of reperfusion. The outcome was evaluated by means of neurological assessment and the extent of lipid peroxidation measuring the plasma malonaldehyde (MDA) together with hydroxyalkenals (HALK). Results: Animals of group HR exhibited a significantly superior neurological outcome compared with those of group C at all three consecutive assessments after reperfusion (post-resuscitation P=0.006, at 8 h P=0.003, and at 24 h P=0.007). The levels of MDA and HALK are lower in the HR group than in group C (P=0.029). Additionally, in the CC group these molecules increased significantly early at hyperoxygenation (P=0.02). A faster lactate metabolism in the HR group was observed during reperfusion, though non-significant. Conclusions: Hypoxemic reperfusion during resuscitation from a severe global ischemic cerebral insult improves the neurological outcome compared with classic hyperoxemic reperfusion. This is additionally confirmed by the decreased production of the molecules of lipid peroxidation. In the absence of preceding ischemia, these molecules may increase by simple over-oxygenation.