[Reoxigenation after neonatal asphyxia with 21% or 100% oxygen in piglets]

Birth asphyxia represents a serious problem worldwide, resulting in 1 million deaths and an equal number of neurologic sequelae annually. It is therefore important to develop new and better ways to treat asphyxia. In the present study we tested the effect of reoxygenation with room air or 100% oxygen following experimental pneumothorax induced asphyxia on blood oxidative stress indicators, early neurologic outcome and cerebral histopathology of newborn piglets. 26 animals were studied in three experimental groups: sham-operated (SHAM, n = 6), reoxygenation with room air after pneumothorax (RORA, n = 10) and reoxygenation with 100% oxygen after pneumothorax (RO100, n = 10). In RORA and RO100 asphyxia was induced under anesthesia with bilateral intrapleural room air insufflation. Gasping, bradyarrhythmia, arterial hypotension, hypoxemia, hypercarbia and severe combined acidosis occurred 62 +/- 6 (RORA) and 65 +/- 7 min (RO100) after the start of the experiments, when the pneumothorax was relieved and ten min of reoxygenation period was started with mechanical ventilation with room air (RORA) or 100% oxygen (RO100). Then the spontaneously breathing animals were followed on room air during the next three hours. Blood oxidative stress indicators--as oxidized and reduced glutathione, plasma hemoglobin and malondialdehyde concentrations--were also measured at different stages of the experiments and early neurologic examinations (neurological score: 20 = normal, 5 = brain dead) were performed at the end of the study. Then the brains were fixed and stained. In SHAM blood gases and acid/base status differed significantly from values measured in RORA and RO100. In RO100 PaO2 was significantly higher at 5 (13.8 +/- 1.8 kPa) and 10 min (13.2 +/- 2.0 kPa) than in RORA (8.7 +/- 0.9, 9.2 +/- 1.0 kPa), respectively. All the measures of oxidative stress indicators remained unchanged in the study groups (SHAM, RORA, RO100). Neurologic examination scores from SHAM were 18 +/- 0, from RORA 13.5 +/- 1.0 and from RO100 9.5 +/- 1.3 (significant differences between SHAM and RORA and RO100, significant difference between RORA and RO100). Cerebral histopathology showed marked damage with similar severity in both asphyxiated groups. We conclude that blood oxidative stress indicators and cerebral histopathology did not differ significantly after 10 min reoxygenation either with room air or with 100% oxygen following pneumothorax induced asphyxia, but reoxygenation with 100% oxygen might impair the early neurologic outcome of newborn pigs.