Determining personalized blood pressure targets during neonatal cardiac surgery with cerebral autoregulation monitoring using transcranial Doppler

Background and Hypothesis:
Brain injury after neonatal cardiac surgery is common, likely caused by hypoxic-ischemic injury due to inadequate perfusion. Monitoring cerebral autoregulation (CA) delineates arterial blood pressure (ABP) limits for compromised cerebral perfusion. These limits of CA can serve as individualized ABP targets to maintain adequate cerebral perfusion. This study aims to evaluate CA estimation using transcranial Doppler (TCD) to establish patient-specific ABP targets.

Materials and Methods:
We monitored ABP and continuously measured cerebral blood flow velocity with TCD during neonatal cardiac surgeries with cardiopulmonary bypass in a prospective cohort study (Wilhelmina Children’s Hospital Utrecht, The Netherlands; ClinicalTrials.gov NCT04713605). Eligible infants were term (age <42 days) or preterm (>32 weeks GA, corrected age <42 days) undergoing (semi-)elective surgery with arterial cannula placement. Exclusion criteria included grade III-IV intracranial haemorrhage, emergency surgery, or lack of parental consent. The mean velocity index (Mx) was calculated every 5
minutes as the Pearson’s correlation coefficient between ABP and cerebral blood flow velocity. Impaired CA was defined as Mx > 0.45. Mx was plotted against mean ABP in 5 mmHg bins to determine the lower limit of autoregulation (LLA), optimal ABP (ABPopt), and upper limit of autoregulation (ULA).

Results:
The mean gestational age was 38.4 weeks (SD = 0.8), with a mean age at surgery of 6.7 days (SD = 2.0), and a mean birth weight of 3398 grams (SD = 338). The mean monitoring duration was 200.8 minutes (SD = 48.6). The mean LLA was 29.4 mmHg (SD = 6.4), mean ABPopt was 42.0 (SD = 7.0) mmHg, and mean ULA was 49.5 (SD = 4.9). The mean duration with impaired CA was 34.1 minutes (SD = 22.1).

Conclusions:
TCD-based CA calculations provide new insights for optimal ABP management in neonates during cardiac surgery. Limits were noticeably narrower than expected.