Objectivesa) To determine if cerebral blood flow is symmetric after internal carotid artery and ipsilateral internal jugular vein ligation in infants during venoarterial extracorporeal life support. b) To determine the cerebral CO2reactivity (open triangle cerebral blood flow/open triangle torr CO2) of neonates during venoarterial extracorporeal life support and its correlation to neurodevelopmental outcome.DesignProspective, clinical study.SettingUniversity hospital pediatric intensive care unit.PatientsFourteen neonates with respiratory failure who were receiving venoarterial extracorporeal life support.InterventionsPaCO2was altered by adjusting the CO2gas flow through the membrane oxygenator. Cerebral blood flow was measured over both parietal-temporal regions at three PaCO2values using xenon-133 clearance methodology. Cerebral blood flow measurements were made early (less than equals 12 hrs of extracorporeal life support, n equals 10) or late (more than equals 48 hrs of extracorporeal life support, n equals 10). In six of 14 infants, both early and late cerebral blood flow rates were measured. PaO2, mean arterial pressure, pump flow rate, and temperature were stable during each study period. Neurodevelopmental outcome was assessed in the neonatal follow-up clinic.Measurements and Main ResultsRight and left hemispheric cerebral blood flow rates were significantly correlated with each other during early and late extracorporeal life support (p equals .0001; r2equals .91). Overall, hemispheric cerebral blood flow was statistically symmetric. There was no association of CO2reactivity (open triangle cerebral blood flow/open triangle torr PCO2, range 0.04 to 1.36 mL/min/100 g/torr) with short-term neurodevelopmental outcome. Infants with normal neurodevelopmental outcome had variable CO2reactivity (range 0.04 to 0.67 mL/min/100 g/torr). Normal short-term neurodevelopmental outcome was observed in two infants with cerebral blood flow of less than 10 mL/min/100 g.ConclusionsHemispheric cerebral blood flow was symmetric in infants during early and late venoarterial extracorporeal life support. Some subgroups showed a trend toward decreased right hemispheric cerebral blood flow, but the small number of patients limited interpretation of this finding. CO2reactivity and cerebral blood flow were highly variable in this population, and were not predictive of short-term neurodevelopmental outcome. Stressed neonates with extremely low cerebral blood flow rates may have relatively normal short-term neurodevelopmental outcome after venoarterial extracorporeal life support.(Crit Care Med 1996; 24:155-162)