Brain oxygenation and metabolism during repetitive apnea with resuscitation of 21% and 100% oxygen in newborn piglets

The oxygen distribution in the microcirculation of the piglet's brain and striatal extracellular dopamine were determined during repetitive apnea and resuscitation with 21% or 100% oxygen. Pre-apnea cortical oxygen was 49.5 +/- 10.4 mm Hg and during each apnea decreased to 8 +/- 0.9 mm Hg. After ten apneic episodes followed by resuscitation with 21% or 100% oxygen, 7.48 +/- 1.6% or 2.6 +/- 0.5% of the tissue volume was below 10 mm Hg, respectively. Extracellular dopamine increased progressively with an increase in the number of apneas with resuscitation of 21% oxygen and at the end of ten apneic episodes it was up to 59,500 +/- 11,320% of control. There was no increase in extracellular dopamine during apnea resuscitated with 100% oxygen. Repetitive apnea caused progressive increase in fraction of hypoxic brain tissue in newborn. The magnitude of the increase is dependent on whether the animals were resuscitated with room air or 100% oxygen.