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.

This study was conducted in accordance with the principles of the Declaration of Helsinki and approved by the Kyoto Prefectural University of Medicine Clinical Ethics Committee in Kyoto, Japan (approval number: ERB-C-2426-1).

The study was designed and received ethical approval to use opt-out consent for all eligible infants born in the participating units. The parents of eligible infants were offered the opportunity to deny the inclusion of the data of their infants in this study.

D.U. and M.Z. designed and performed the experiments. M.O. and E.I. contributed to the data collection. A.Y. contributed to the statistical analyses. D.U. wrote the initial draft of the manuscript in consultation with M.Z. All other authors contributed to the interpretation and critical review of the manuscript and approved the final version of the manuscript, and shared accountability for all aspects of the work to ensure that questions related to the accuracy or integrity of any part of the work were appropriately investigated and resolved.

Received: 15 January 2025

Accepted: 22 July 2025

Accepted Manuscript online:
23 July 2025

Article published online:
04 August 2025

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