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 birth weight, 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.

CBF velocity in newborns 23–24 weeks' gestation during the first week of life

“…In 17 "healthy" normocapnic (35-50 mm Hg) ventilated infants born at 24-28 weeks' gestation, Pezzati et al [6] reported that middle cerebral artery mean CBFv during the first 2-8 hours was 10 ± 3 cm/sec, which is similar to our initial and earliest value of 10.1 (95% CI 6.8-13.3) cm/sec for [23][24] week infants, at ∼6 hours of age. "Healthy" infants were described as those without significant maternal pregnancy complications, intrauterine growth restriction, malformations, perinatal asphyxia, infection, thrombocytopenia, anemia, polycythemia, hypotension, hypertension, intraventricular hemorrhage (IVH) ≥grade 2, or hemodynamically significant patent ductus arteriosus [6]. Measurements were always performed ≥1 hour after surfactant administration [13].…”

“…While CBFv reference values have not been previously reported for infants this immature, one study examined middle cerebral artery CBFv in relatively stable premature infants born at 24-28 weeks' [6]. In 17 "healthy" normocapnic (35-50 mm Hg) ventilated infants born at 24-28 weeks' gestation, Pezzati et al [6] reported that middle cerebral artery mean CBFv during the first 2-8 hours was 10 ± 3 cm/sec, which is similar to our initial and earliest value of 10.1 (95% CI 6.8-13.3) cm/sec for [23][24] week infants, at ∼6 hours of age.…”

“…To collect a sample of infants born at this early gestational age not exposed to any maternal conditions or medications that could influence CBFv would take years and would not reflect "average" 23-24 week survivors. Moreover, the previous studies of slightly more mature infants also suffered from enrolling infants and pregnancies exposed to conditions such as IVH [6] and prophylactic ibuprofen and caffeine [7]. Lastly, middle cerebral artery CBFv reference curves may only be relevant to a few research groups.…”

“…Unfortunately, many survivors develop brain injury and have poor longterm neurodevelopmental outcomes [3]. Due to the association between disturbances of cerebral blood flow (CBF) and the development of brain injury [4,5], CBF velocity (CBFv) during the early neonatal period in premature infants has been extensively studied [6][7][8][9][10][11][12]. This is important because understanding the normal developmental pattern of CBFv changes may aid in assessing how disturbed CBF may be associated with brain injury.…”

NeoDoppler: New ultrasound technology for continuous cerebral circulation monitoring in neonates

“…Whether or not flow indices are good indicators to assess cerebral hemodynamics remains controversial. 11,33,35,36 In neonatology, RI has been used to predict outcome in infants with neonatal encephalopathy. A low RI (<0.55) has been associated with poor neurological outcome, 37 but this association appears weaker during therapeutic hypothermia.…”