Electrocortical brain activity during hypoxia and hypotension in anesthetized newborn lambs

Blood gas and blood pressure disturbances do influence cerebral blood flow in newborns. To what extent cerebral blood flow changes affect electrocortical brain activity remains uncertain. We studied the effect of severe hypoxia and hemorrhagic hypotension on carotid artery blood flow and electrocortical brain activity in newborn anesthetized lambs. During hypoxia carotid artery blood flow increased significantly, whereas electrocortical brain activity remained unchanged. The hemorrhagic hypotension study showed that the lower limit of the autoregulatory ability of the cerebral vascular bed was 60 mmHg. Electrocortical brain activity however remained stable until mean aortic pressure had dropped below 30 mmHg, carotid artery blood flow below 10.6 ml/kg/min, and cerebral oxygen delivery below 1.4 ml/kg/min.