Aim: To determine the range of cerebral blood flow velocities (CBFVs) and Doppler indices of cerebrovascular resistance in normal-term neonates as a baseline for a study of hypoxic-ischaemic encephalopathy. Methods: The CBFVs, resistive index (RI) and pulsatility index (PI) were measured in the anterior and middle cerebral arteries (ACA and MCA) of 38 normal neonates. Results: The mean peak systolic, end diastolic and time-averaged velocities (PSV, EDV and TAV) were 36.3 AE 6.6, 12.4 AE 3.9 and 22.0 AE 4.0 cm/s (ACA) and 41.4 AE 13.2, 13.0 AE 5.5 and 25.8 AE 7.9 cm/s (MCA), respectively. All CBFVs in the ACA correlated with gestation; only EDV was correlated to post-natal age. The RI in the ACA (0.67 AE 0.06) and MCA (0.68 AE 0.07) were correlated (r = 0.72, P < 0.001); RI correlated to postnatal age. Two infants with RI < 0.55 were both fed within 25 mins of the study; RI correlated with post-prandial time (dichotomous, pivot 25 min). The mean PI was 1.11 AE 0.18 (ACA) and 1.17 AE 0.23 (MCA). Correlations were observed with post-natal age and post-prandial time (dichotomous). The average angle of insonation was greater in the ACA than in the MCA (median of 5 vs. 18 ).Conclusions: Results corresponded with previous published studies. No correlation was observed between Doppler indices and gestation as component velocities all increase with advancing gestation. Less variation and smaller standard deviation of CBFV's was associated with a smaller angle of insonation. Low RIs (<0.55), without a pathological cause, warrants further study.Key words: cerebral arteries; cerebrovascular circulation; infant, newborn; ultrasonography, Doppler, transcranial; vascular resistance. What is already known on this topic1 The resistive index (RI) is an accepted indicator of cerebrovascular resistance. 2 In previous studies, the normal RI in term neonates has been established to be greater than 0.55. 3 An RI lower than 0.55 may be observed after periods of hypoxia. What this paper adds1 It is preferable to measure cerebral blood flows in the anterior cerebral artery as they exhibit less variance and are therefore more reproducible than middle cerebral artery measurements. 2 Low RIs that may be considered clinically significant (RI < 0.55) were observed in two normal infants without a known pathological cause. 3 The RI and PI can remain unchanged if component velocities decrease or increase together.The Doppler indices, the resistive index (RI) and the pulsatility index (PI) are considered a measure of downstream cerebrovascular resistance (CVR) and provide a non-invasive means of investigating the neonatal circulation. 1 These indices are calculated from the cerebral arterial velocities measured using Doppler in the neonate through the 'acoustic windows,' the fontanelles and sutures of the skull. Pourcelot's resistive (resistance) index (RI) is the ratio of the difference in pulsatile flow velocities, peak systolic velocity (PSV) -end diastolic velocity (EDV), divided by the PSV 5,6 :The PI of Gosling (PI) is a ratio of the dif...

Aim To assess cerebral oxygenation in premature infants who are transitioning from nasal continuous positive airway pressure (nCPAP) to heated humidified high‐flow nasal cannula therapy (HFNC). Methods A prospective observational study done in a single‐centre neonatal intensive care unit (NICU). Regional cerebral oxygen saturations (RcSO2) were measured using frequency‐domain near‐infrared spectroscopy (FD‐NIRS) in very low birthweight (VLBW) premature infants born at <32 weeks transitioning from nCPAP to HFNC. Results Median gestational age was 27 weeks and median birthweight was 924 g. Recordings were performed at a median gestational age of 30 weeks and a median postnatal age of 10 days. Median weight at study entry was 1111 g. Cerebral oxygenation was not significantly different in infants transitioning from nCPAP to HFNC (66% vs 66%). Conclusion No difference in cerebral oxygenation in premature infants transitioning from nCPAP to HFNC was observed. This finding is reassuring and further supports the use of HFNC in preterm infants.