Dynamic cerebral autoregulation in infants undergoing major non-cardiac surgery

Dynamic cerebral autoregulation (CAR) is the capacity in the cerebral vessels to attenuate the effect of rapid changes in blood pressure (BP). NeoDoppler, a novel ultrasound system, monitors cerebral blood flow velocity (CBFV) through an open fontanel continuously. Our primary aim was to evaluate dynamic CAR using continuous Doppler in infants undergoing major non-cardiac surgery. The pressure-flow relationship was evaluated in the time- and frequency domain, and the two methods were compared. The secondary aim was to compare this with near-infrared spectroscopy (NIRS). CBFV and regional oxygenation were synchronized with invasive BP monitoring. Nineteen infants (ten preterm) were included. In the time-domain, NeoDoppler showed that the mean proportion of time with impaired CAR was highest during surgery (0.59, 95% CI 0.48-0.70) compared with anesthesia before start of surgery (0.41, 95% CI 0.31-0.52, p = 0.040), and recovery (0.25 95% CI 0.13-0.36, p < 0.001). There was no evidence of different time profiles when using NeoDoppler in the time- versus the frequency domain (p = 0.165), or between NeoDoppler and NIRS in the time-domain (p = 0.167). In contrast to NIRS, NeoDoppler enabled direct evaluation of the cerebrovascular reactivity. Continuous Doppler monitoring combined with invasive BP monitoring enables a unique possibility to evaluate the pressure-flow relationship.