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

Background and purpose: Reactive oxygen species contribute to membrane lipi d peroxidation and neuronal death and have been implicated in anoxic enceph alopathy. We tested whether hypoxemic reperfusion (HR) after global cerebra l ischemia would improve neurological recovery. Methods: Two groups of pigs (n = 11 in each group) were subjected to a mode l of a 10-min global cerebral and systemic ischemia to compare the effect o f 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 respe ctive period of reperfusion. The outcome was evaluated by means of neurolog ical assessment and the extent of lipid peroxidation measuring the plasma m alonaldehyde (MDA) together with hydroxyalkenals (HALK). Results: Animals of group HR exhibited a significantly superior neurologica l outcome compared with those of group C at all three consecutive assessmen ts after reperfusion (post-resuscitation P = 0.006, at 8 h P = 0.003, and a t 24 h P = 0.007). The levels of MDA and HALK are lower in the HR group tha n in group C (P = 0.029). Additionally, in the CC group these molecules inc reased significantly early at hyperoxygenation (P = 0.02). A faster lactate metabolism in the HR group was observed during reperfusion, though non-sig nificant. Conclusions: Hypoxemic reperfusion during resuscitation from a severe globa l ischemic cerebral insult improves the neurological outcome compared with classic hyperoxemic reperfusion. This is additionally confirmed by the decr eased production of the molecules of lipid peroxidation. In the absence of preceding ischemia, these molecules may increase by simple over-oxygenation .