The prediction of estimated cerebral perfusion pressure with trans-systolic time in preterm and term infants.

It is important to monitor cerebral perfusion in infants because hypo- and hyperperfusion can contribute to neurological injury. This study aimed to clarify the relationship between trans-systolic time (TST) and critical closing pressure (CrCP) or estimated cerebral perfusion pressure (CPPe) in neonates. Moreover, we aimed to determine the TST values in preterm and term infants with stable cerebral perfusion to clarify normative reference data. This multicentre prospective study included infants with arterial lines admitted to the neonatal intensive care units between December 2021 and August 2023. TST, CrCP, and CPPe were calculated using middle cerebral artery waveforms recorded using transcranial Doppler ultrasonography when clinicians collected arterial blood samples. Three hundred and sixty samples were obtained from 112 infants with a gestational age of 32 (interquartile range, 27-37) weeks and a birth weight of 1481 (956-2355) g. TST was positively correlated with CPPe (r = 0.60, p < 0.001), but not with CrCP (r = 0.08, p = 0.10). The normative reference values of TST in preterm and term infants without samples of hyper- or hypocapnia and/or hyper- or hypotension, which may affect cerebral perfusion, were as follows: ≤ 29 weeks, 0.12 (0.11-0.14) s; 30-36 weeks, 0.14 (0.12-0.15) s; and ≥ 37 weeks, 0.16 (0.14-0.17) s, respectively.  Conclusion: TST in neonates significantly correlated with CPPe, but not with CrCP. TST may be a good predictor of cerebral perfusion and potentially have wider clinical applications. What is Known: • Trans-systolic time (TST) is used in evaluating the effects of increased intracranial pressure on cerebral haemodynamics. However, little is known about the efficacy of TST in predicting neonatal cerebral perfusion pressure. What is New: • This study added evidence that TST correlated with estimated cerebral perfusion pressure, but not with critical closing pressure. Additionally, we showed the normative reference values of the TST in preterm and term infants.

Ventilated Infants Have Increased Dead Space and Lower Alveolar Tidal Volumes during the Early versus Recovery Phase of Respiratory Distress.

BACKGROUND: Few studies have reported the measurement of anatomical dead space (Vd,an) and alveolar tidal volume (VA) in ventilated neonates with respiratory distress. OBJECTIVE: The aim of this study was to determine the differences in Vd,an and VA in ventilated infants between the early and recovery phases of respiratory distress using volumetric -capnography (Vcap) based on ventilator graphics and capnograms. METHODS: This study enrolled twenty-five ventilated infants (mean birth weight, 2,220 ± 635 g; mean gestational age, 34.7 ± 3.3 weeks). We adjusted respiratory settings to maintain appropriate oxygenation and tidal volume (VT), and performed Vcap based on waveforms of ventilator graphics and capnograms. Vd,an and VAwere measured in infants with respiratory disorders, immediately after intubation (early phase) and subsequently when they were clinically stable (recovery phase). RESULTS: The early phase, with lower dynamic lung compliance, required a higher level of ventilator support, not positive end-expiratory pressure, than the recovery phase. There were significant differences between the early and recovery phases for Vd,an (mean difference in Vd,an/kg = 0.57 mL/kg; 95% confidence interval [CI], 0.38-0.77; mean difference in Vd,an/VT = 0.10; 95% CI, 0.07-0.14) and VA (mean difference in VA/kg = -0.60 mL/kg; 95% CI, -0.94 to -0.27; mean difference in VA/VT = -0.12; 95% CI, -0.15 to -0.09), despite no difference in VT. CONCLUSIONS: We evaluated changes in Vd,an and VA during mechanical ventilation using Vcap based on waveforms. The increase in Vd,an and decrease in VA suggested dilation of the airways and collapse of the alveoli in ventilated infants with low lung compliance.