Impact of cardiopulmonary bypass on cerebrovascular autoregulation assessed by ultrafast ultrasound imaging.

Newborns with congenital heart disease undergoing cardiac surgery are at risk of neurodevelopmental impairment with limited understanding of the impact of intra-operative cardiopulmonary bypass (CPB), deep hypothermia, and selective cerebral perfusion on the brain. We hypothesized that a novel ultrasound technique, ultrafast power Doppler (UPD) can assess variations of cerebral blood volume (CBV) in neonates undergoing cardiac surgery requiring CPB. UPD was performed before, during and after surgery in newborns with hypoplastic left heart syndrome undergoing a Norwood operation. We found that global CBV was not significantly different between patients and controls (p = 0.98) and between pre- and post-operative (p = 0.62). UPD was able to monitor changes in CBV throughout surgery, revealing regional differences in CBV during hypothermia during which CBV correlated with CPB flow rate (R 2 = 0.52, p = 0.021). Brain injury on post-operative MRI was observed in patients with higher maximum variation in CBV. Our findings suggest that UPD can quantify global and regional brain perfusion variation during neonatal cardiac surgery with this first intra-operative application demonstrating an association between CBV and CPB flow rate, suggesting loss of autoregulation. Therefore, measurement of CBV by UPD could enable optimization of cerebral perfusion during cardiac surgery in neonates. KEY POINTS: Impact of cardiopulmonary bypass on the neonatal brain undergoing cardiac surgery is poorly understood Ultrafast power Doppler quantifies cerebral blood volume, a surrogate of brain perfusion Cerebral blood volume varies throughout cardiopulmonary bypass surgery and is associated with variation of the bypass pump flow rate during deep hypothermia Association between cerebral blood volume and bypass pump flow rate suggests loss of cerebrovascular autoregulatory processes. Quantitative monitoring of cerebral perfusion by ultrafast power Doppler could provide a direct parameter to optimize cardiopulmonary bypass flow rate Abstract figure legend Cerebral blood volume during neonatal cardiopulmonary bypass assessed by ultrafast power Doppler. Using freehand transfontanellar ultrafast power Doppler, cerebral blood volume is shown to vary throughout and immediately following neonatal cardiopulmonary bypass surgery and is associated with the variation of the cardiopulmonary bypass flow rate during induced deep hypothermia. This association suggests loss of cerebrovascular autoregulatory mechanisms which could be linked with acquired brain injury. This article is protected by copyright. All rights reserved.