CEREBRAL BLOOD-FLOW AND EVOKED-POTENTIALS DURING REOXYGENATION WITH 21-PERCENT OR 100-PERCENT O2 IN NEWBORN PIGS

The effects of resuscitation with 21 or 100% O2 on cerebral blood flow (CBF) and somatosensory evoked potentials (SEPs) were studied in 19 n ewborn pigs anesthetized with pentobarbital sodium. They were ventilat ed with 8% O2 until base excess reached -20 mmol/l and then were rando mly reoxygenated with 21% O2 (n = 10) or 100% O2 (n = 9) for 25 min fo llowed by 21% O2. Mean duration of hypoxemia in the two groups was 57 +/- 6 (SE) and 59 +/- 6 min, respectively. CBF determined by radioacti ve microspheres was significantly increased in all areas in both group s after 5 and 20 min of reoxygenation. At 5 min of reoxygenation foreb rain O2 uptake (CMRO2) had increased significantly compared with basel ine values in the 21% O2 group (2.5 +/- 0.1 to 3.2 +/- 0.2 ml . 100 g- 1 . min-1) but not in the 100% O2 group. There were, however, no signi ficant differences between the two groups in CBF or CMRO2 at any time, and by 60 min of reoxygenation both had returned to baseline levels. SEPs were not significantly different in the two groups. We conclude t hat, as judged by CBF, CMRO2, and SEP, 21% O2 is not inferior to 100% O2 when hypoxemic newborn pigs are reoxygenated.