Cerebral blood flow and carbon dioxide reactivity in neonates during venoarterial extracorporeal life support

Objectives: a) 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 CO₂ reactivity (A cerebral blood flow/Δ torr CO₂) of neonates during venoarterial extracorporeal life support and its correlation to neurodevelopmental outcome. Design: Prospective, clinical study. Setting: University hospital pediatric intensive care unit. Patients: Fourteen neonates with respiratory failure who were receiving venoarterial extracorporeal life support. Interventions: Paco₂ was altered by adjusting the CO₂ gas flow through the membrane oxygenator. Cerebral blood flow was measured over both parietal-temporal regions at three Paco₂ values using xenon-133 clearance methodology. Cerebral blood flow measurements were made early (≤12 hrs of extracorporeal life support, n = 10) or late (≥48 hrs of extracorporeal life support, n = 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 Results: Right and left hemispheric cerebral blood flow rates were significantly correlated with each other during early and late extracorporeal life support (p = .0001; r² = .91). Overall, hemispheric cerebral blood flow was statistically symmetric. There was no association of CO₂ reactivity (A cerebral blood flow/Δ 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 CO₂ reactivity (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 <10 mL/min/100 g. Conclusions: Hemispheric 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. CO₂ reactivity 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.