Using the Cerebrovascular Time Constant to Assess Cerebral Perfusion in Neonates

This study aimed to investigate the relationship between the cerebrovascular time constant (Tau) and estimated cerebral perfusion pressure (CPPe) in neonates and clarify the normative reference data of Tau for different gestational ages.This multicenter, prospective study included infants with arterial lines who were admitted to neonatal intensive care units between December 2021 and May 2024. Tau and CPPe were calculated based on middle cerebral artery waveforms obtained using transcranial Doppler ultrasonography when clinicians collected arterial blood samples.A total of 432 samples were obtained from 127 infants with a median gestational age of 32 weeks (interquartile range [IQR]: 28-37 weeks) and a median birth weight of 1,566 g (IQR: 932-2,334 g). Tau demonstrated a significant correlation with CPPe across the following gestational age groups: ≤29 weeks, r = -0.49 and p < 0.001; 30 to 36 weeks, r = -0.61 and p < 0.001; and ≥37 weeks, r = -0.56 and p < 0.001. Despite this correlation, the median Tau was consistent across gestational ages, and the following normative reference values were observed: ≤29 weeks, 0.178 ± 0.046 seconds; 30 to 36 weeks, 0.186 ± 0.045 seconds; ≥ 37 weeks, 0.176 ± 0.037 seconds; and all weeks, 0.180 ± 0.044 seconds.Tau may serve as an effective parameter for evaluating cerebral perfusion in neonates. · Tau correlates with CPPe across gestational ages. · The median Tau value was consistent at 0.18 seconds.. · Tau is useful for cerebral perfusion evaluations..