The effects of resuscitation with 21 or 100% O2 on cerebral blood flow (CBF) and somatosensory evoked potentials (SEPs) were studied in 19 newborn pigs anesthetized with pentobarbital sodium. They were ventilated with 8% O2 until base excess reached -20 mmol/l and then were randomly reoxygenated with 21% O2 (n = 10) or 100% O2 (n = 9) for 25 min followed by 21% O2. Mean duration of hypoxemia in the two groups was 57 +/- 6 (SE) and 59 +/- 6 min, respectively. CBF determined by radioactive microspheres was significantly increased in all areas in both groups after 5 and 20 min of reoxygenation. At 5 min of reoxygenation forebrain O2 uptake (CMRo2) had increased significantly compared with baseline 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 significant 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 that, as judged by CBF, CMRo2, and SEP, 21% O2 is not inferior to 100% O2 when hypoxemic newborn pigs are reoxygenated.

Although hyperoxia is considered a major risk factor for the development of ROP (4), experimental data and clinical studies have also pointed at other factors. Thus, hypercarbia (4), hypocarbia (5) and hypoxemia (6, 7) have been associated with the development of ROP.At least some putative major risk factors in the development of ROP affect cerebral and ocular blood flow (8,9). Experimental work with adult cats, as well as with newborn lambs and piglets, has shown that hypercarbia influences ocular and cerebral blood flows, although the blood flow response in the retina may differ from that of the choroid (10-12). However, studies on ocular blood flow in the neonate are few (13), and to our knowledge there are no reports on the influence of hypocarbia on ocular blood flow in the neonatal period.Hypocarbia and hypercarbia have opposite effects on cerebral vasculature, hypercarbia increasing cerebral blood flow, hypo-

Cerebral blood flow during experimental hypoxaemia and ischaemia in the newborn piglet. Acta Paediatr Scand Suppl360: 13, 1989. The effect of selective hypoxaemia or ischaemia on cerebral blood flow was studied in 14 newborn piglets with the microsphere method. Surgery and experiments were performed under general anesthesia with 70 % nitrous oxide. The spontaneously breathing piglet was then exposed to either low (zero) oxygen in the inspired air (hypoxaemia), or a graded tourniquet (3-5 kg string weight) of the neck above the level 14 J.-P. Odden et al. Acta Paediatr Scand Suppl 360 ~~ ~

Our aim was to determine whether the use of room air or 100% oxygen has different effects on the peripheral circulation during resuscitation from severe hypoxemia. Twenty-four piglets, 2-to 5-days old, were anesthetized with pentobarbital and randomized to control (n = 5, surgery only) or hypoxemia. Hypoxemia (FiO2 = 0.08) was continued until base excess reached - 20 mml/L. Resuscitation was then performed with 21% (n = 10) or 100% O2 (n = 9) for 25 min followed by 21% O2 in both groups. Regional blood flow was measured with radioactive microspheres. Both hypoxic groups showed marked hyperemia during resuscitation in cardiac and skeletal muscle, a moderate hyperemia in intestine and pancreas while kidneys, liver, spleen and skin showed no hyperemic response. There were no significant differences between the two treatment groups in blood flow to any organ. Arterial oxygen content was significantly higher in the 100% O2 group than in the 21% O2 at 5 and 20 min after onset of resuscitation (11.6 +/- 0.7 and 11.2 +/- 0.6 vs 8.6 +/- 0.3 and 8.7 +/- 0.3 ml/100 ml, p < 0.01). Oxygen delivery was, however, significantly higher in the 100% O2 group than in the 21% O2 group only to the intestine and pancreas at 5 min of resuscitation. We conclude that resuscitation with 21% or 100% oxygen produces similar changes in peripheral blood flow in this porcine model of neonatal hypoxemia.

No abstract