Reoxygenation with 100 or 21% oxygen after cerebral hypoxemia-ischemia-hypercapnia in newborn piglets.

We tested if reoxygenation with 100% O(2) was superior to 21% O(2) after combined cerebral hypoxemia-ischemia-hypercapnia (HIH) in newborn piglets. Twenty-eight piglets were randomized to reoxygenation with 100 or 21% O(2) following asphyxia. Asphyxia was induced by ventilation with 8% O(2), adding CO(2), and temporary occlusion of both common carotid arteries. After 20 min, reoxygenation-reperfusion was started with 21% O(2) (HIH 21% group, n = 13) or 100% O(2) (HIH 100% group, n = 11) for 30 min followed by 21% O(2). All piglets were observed for 2 h. We measured mean arterial blood pressure (MABP), changes in microcirculation in the cerebral cortex (laser Doppler), and extracellular concentrations of hypoxanthine in the cortex and amino acids in the striatum (microdialysis). We found significantly higher MABP and better restoration of microcirculation after reoxygenation with 100% compared with 21% O(2), but no differences in biochemical markers were found between the groups. This indicates that the brain tolerated reoxygenation with 21% as well as with 100% O(2) in the present model of experimental asphyxia in spite of the differences in MABP and cerebral microcirculation. Copyright 2004 S. Karger AG, Basel