Background: To seek direct evidence for nitric oxide (NO) release and its relationship to cerebral blood flow (CBF) in neonatal porcine brain tissue during resuscitation in two different resuscitation models.

Subjects: Newborn anaesthetized piglets, age 1-2 days, were randomized into three groups.

Interventions: The piglets were ventilated with 6% O2 for minimum of 20 min and resuscitated when BE was ≤20 mmol/L. Serial blood flow in forebrain cortex was measured using a multichannel laser-Doppler system. A highly spesific amperiometric sensor permitting specific NO-measurement was inserted in the cortex. Observations were made continuously at baseline. during hypoxemia, and during 30 min of reoxygenation with respectively 100% (n=8) or 21% (n=9) O2. As controls six healthy piglets were studied.

Results: Mean of left and right frontal LD-flow increased(mean±SEM) 112±8% (p<.05) when hypoxemia was induced, and decreased slowly after 5-10 minutes to 69 ±14% (p<.05). During reoxygenation no differences between the groups were found. No-activity decreased rapidly when hypoxemia was induced (52%, p<.05). After 30 min of reoxygenation the NO level was significantly higher than baseline in the 100% group (128 ±1%, p<.05) in contrast to the 21% group which reached baseline (85±2%).

Conclusion: Reoxygenation with 21% O2 restores cerebral blood flow as efficiently as 100% O2. The higher NO-level during reoxygenation with 100% O2 compared with 21% O2 may indicate a higher production of peroxynitrite radicals.