The influence of acute hypoxemia and hypovolemic hypotension of neuronal brain activity measured by the cerebral function monitor in newborn piglets.

Little is known about the cerebral electrical response to short periods of hypoxemia, hypotension and their combination. These conditions occur frequently in critically ill newborn infants; their cerebral electrical activity can be registrated easily with the Cerebral Function Monitor (CFM). Therefore we recorded on-line cortical electrical activity during hypoxemia and hypotension in 11 newborn piglets aged 13-18 days. Hypoxemia was induced by reducing inspired oxygen fraction. Hypotension was induced by withdrawal of blood. The experimental groups were: Group I: arterial oxygen saturation (SaO2) 45-85%, group II: SaO2 < 45%, group III: mean arterial pressure (MAP) 50-75 mmHg, group IV: MAP < 50 mmHG, group V: SAO2 < 85% and MAP 50-75 mmHg and group VI: SaO2 < 85% and MAP < 50 mmHg. CFM registrated normal cortical electrical activity during periods of moderate or severe hypoxemia (group I and II) and during isolated moderate hypotension (group III). The cortical activity decreased significantly due to severe hypotension alone (group IV) and combined hypotension and hypoxemia (group V and VI). Hypotension has a more potent effect on cortical electrical activity than hypoxemia in the newborn piglet. Cerebral electrical activity does not change during severe hypoxemia and moderate hypotension possibly due to cerebral flow regulation. CFM recorded decreased cerebral electrical activity during severe hypotension and hypotension with hypoxemia. CFM could provide invaluable data in severely ill newborns.