Reoxygenation with Oxygen (100% O₂) on the Cardiac Output Distribution(COD) after acute Hypoxia 315

Introduction: Routine use of oxygen shortly after birth might cause extra oxidative stress. This study investigates the changes of fraction of COD to different organs during reoxygenation under hyperoxic conditions after exposure to acute hypoxia. Methods: Fertile White Leghorn eggs were studied at two incubation time groups (TG1, d14-16 (n=13) and TG2, d17-19(n=12), total incubation time is 21d). A branch of the chorioallantoic vein was catheterized. The cardiac output distribution was measured with fluorescent microspheres injected during normoxia, at the end of 5 minutes period hypoxia (100% N₂) and after 5 minutes of hyperoxic reoxygenation(100% O₂). Results: Are presented in the table. Conclusion: Hypoxia caused a redistribution of the cardiac output in favour of the brain, heart and lungs. Contrary to reoxygenation with 21% O₂, when the CO is redistributed in favour of the brain, heart and intestine¹, reoxygenation with 100% O₂ caused a redistribution in favour of the brain and intestine only. This might be the result of a local protective mechanism to hyperoxia in the heart tissue.

Table 1 Table: Mean percentage (%) of the fraction of COD during hypoxia and reoxygenation. (CAM=chorioallantoic membrane)(*p<0.05 increased compared to normoxia;**p<0.05 decreased compared to normoxia).