Cerebral Critical Closing Pressure During Neonatal Cardiac Surgery: a Comparison of The 2-Point, First Harmonic and Impedance Method

Background / Hypothesis:<br/>Neonatal critical congenital heart disease (CHD), requiring cardiopulmonary bypass (CPB) surgery, poses risks as new postoperative white matter injury (WMI) and long-term neurological impairment. Patient-specific arterial blood pressure (ABP) targets, based on cerebral autoregulatory limits and cerebral critical closing pressure (CrCP), may improve cerebral perfusion and reduce complications. This pilot study assesed CrCP-determination plausibility and accuracy in neonates during CHD surgery. We hypothesized that the physiology-based impedance method was the most plausible and accurate for CrCP calculation.<br/><br/>Materials and Methods:<br/>Ten neonates from the prospective FLOWER cohort study undergoing (semi-)elective CHD surgery were selected (Wilhelmina Children’s Hospital Utrecht, The Netherlands; ClinicalTrials.gov NCT04713605). Inclusion criteria: neonates &lt;42 days old, gestational age &gt; 32 weeks, excluding Grade III-IV intracranial hemorrhage. Patient characteristics and a 10-minute epoch of invasive ABP, electrocardiogram and cerebral blood flow velocity (CBFV) from transcranial doppler were collected pre- and post CPB. CrCP was calculated by two-point (2P), first harmonic (1H), and impedance methods. The number of negative (unphysiological) values were compared. Observed CrCP (OCrCP) values (scored independently by three authors) were derived from CBFV-ABP plots where CBFV reached zero. Methods were compared to OCrCP via regression, correlation, and Bland-Altman plots. <br/><br/>Results:<br/>The impedance method showed 0% negative values versus 17.7% (1H) and 17.0% (2P). It correlated best with OCrCP (0.92 versus 0.86 for 1H and 2P) and showed the smallest bias, while both other methods showed proportional bias. Impedance CrCP was 26.8 mmHg (IQR 8.54) pre- CPB and 28.1 mmHg (IQR, 6.4) post-CPB. <br/><br/>Conclusions:<br/>The impedance method is the most plausible and accurate method for CrCP calculation in neonatal CHD surgery. Found CrCP values near mean ABP support its role as a key perfusion modulator; small ABP drops may cease flow. Intersubject variability highlights the need for individualized blood pressure targets to optimize cerebral perfusion management and reduce postoperative neurological injury.<br/>