Experimental study on the hemodynamics of the neonatal brain

The effects of inhalation of different gases were studied in neonatal rabbits with the following results: In neonates with normal heart rate (HR), hyperoxia induced by O2 inhalation did not appreciably affect HR, but it increased cerebral tissue PO2, while decreasing cerebral blood flow (CBF). In many of those which fell into a state of marked bradycardia, not only HR and CBF but also cerebral tissue PO2 levels were recovered as a result of O2 inhalation. CBF was increased even when HR was hardly changed (at least when the HR decrease was 10% or less) by hypercarbia due to inhalation of CO2 mixed air. Severe hyperoxia induced by N2O inhalation caused bradycardia and reduced CBF.