Using the cerebrovascular time constant to assess cerebral perfusion in neonates.

Objective: 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.

Study design: 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.

Results: 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; 30-36 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 s; 30-36 weeks, 0.186 ± 0.045 s; ≥37 weeks, 0.176 ± 0.037 s; and all weeks, 0.180 ± 0.044 s.

Conclusion: Tau may serve as an effective parameter for evaluating cerebral perfusion in neonates.