Early postnatal Doppler assessment of cerebral blood flow velocity in healthy preterm and term infants

Abstract

The aim of the present study was to generate normal reference data for anterior and middle cerebral artery blood flow velocity and resistance index in preterm and term infants during the first 8 hours of life. The study population longitudinally included 120 healthy preterm and term infants (gestational age 24 to 41 weeks), all of appropriate weight for gestational age. The following parameters were studied: peak-systolic velocity, end-diastolic velocity, mean velocity, and resistance index. All parameters were measured in the anterior cerebral artery, in the left middle cerebral artery, and in the right middle cerebral artery with the use of Doppler colour ultrasonography. In addition, we studied the ratio of mean arterial blood pressure to mean velocity in the three cerebral arteries as a further estimate of cerebral relative vascular resistance. We found that cerebral blood flow velocities increased significantly with increasing gestational age and birthweight, both in the anterior cerebral artery and in the right and left middle cerebral arteries. Resistance index, both in the anterior cerebral artery and in the middle cerebral arteries, increased significantly only with increasing gestational age. Relative vascular resistance decreased significantly with increasing gestational age and birthweight in the three cerebral arteries. Significant differences were found (p<0.05) in these values between the anterior cerebral artery and the middle cerebral arteries. The narrow time frame (2 to 8 hours) that we used to evaluate cerebral blood flow velocity often represents a significant moment at which decisions are made that can be fundamental for the outcome of the newborn infant.

Color doppler evaluation of the influence of type of delivery, sex, postnatal age and time post feeding on full term healthy newborns cerebral blood flow

“…Pezzati et al 6 and Bokiniec et al 8 , reported that there was no difference in CBFV in both brain hemispheres in healthy term neonates. Assis, et al 13 described no significant difference in RI between right and left ACA and MCA in a group of 45 preterm healthy newborns.…”

“…Studies has shown that there was no correlation between the mean blood pressure and mean blood flow velocity in cerebral arteries, and that this change is likely to represent a normal adaptive response of the cerebral circulation to postnatal life, when the efficiency of the CBF autoregulatory response in general improved with increasing age and maturity of the brain 6,25 . In the 50 full term healthy newborns studied between 12h and 72h of life, the results showed not statistically differences on CBFV, PI and RI.…”

“…The majority of investigators use RI as a indicative of cerebrovascular resistance because it minimizes the effect of transducer placement and can be easily obtained without velocity signal calibration 6 . The pulsatility index, PI, is an arterial blood-flow velocity waveform index designed by Gosling,et al 10 , to quantify the pulsatility or oscillations of the waveform.…”

“…The CBFV in term healthy newborns increased with increasing gestational age, postnatal age and birthweight, and the RI increased significantly with increasing gestational age [6][7][8] . However, limited information is available regarding influence of other factors such as type of delivery, sex, postnatal age and feeding on CBFV, RI and pulsatitility index (PI) in neonates.…”

Velocimetria Doppler no período neonatal em recém-nascidos a termo pequenos para idade gestacional

“…Baseado em tais evidências, o presente estudo foi concebido com o objetivo de avaliar a velocidade de fluxo sanguíneo cerebral (FSC) através do mó-dulo Doppler realizado entre 24-48 horas de vida e a possível associação com algumas variáveis maternas e perinatais em RN a termo PIG, comparando os resultados com aqueles obtidos em RN adequados para idade gestacional (RN AIG), com a finalidade de utilizá-lo futuramente como instrumento de predição do risco no período neonatal para alterações no território vascular cerebral correspondente e o prognóstico neurológico em médio e longo prazo. As ACA e ACM foram localizadas anatomicamente pelo módulo bidimensional do ultra-som e detectadas as ondas de fluxo sanguíneo através do módulo de Doppler pulsado 9 . A ACA foi visualizada através da janela transfontanelar anterior, na região pericalosa e a ACM foi aferida na região temporal, ao nível do polígono de Willis.…”