Impaired Chemical Coupling of Cerebral Blood Flow Is Compatible with Intact Neurological Outcome in Neonates with Perinatal Risk Factors

Abstract

Early detection of pathophysiological factors associated with permanent brain damage is a major issue in neonatal medicine. The aim of our study was to evaluate the significance of the CO₂ reactivity of cerebral blood flow (CBF) in neonates with perinatal risk factors. Fourteen ventilated neonates with perinatal risk factors (pathological cardiotocogramm, low cord pH, postpartal encephalopathy) were enrolled into this prospective study. The study was performed 18–123 h after birth. CBF was measured using the nonivasive intravenous ¹³³Xe method. Two measurements were taken with a minimal PaCO₂-difference of 5 mm Hg. From the two CBF values the CO₂ reactivity was calculated. Outcome was evaluated 1 year after birth. The CBF values at a lower PaCO₂ ranged from 6.6 to 115.2 ml/100 g brain issue/min (median = 18.2) and at a higher PaCO₂ level from 7.1 to 125.7 ml/100 g brain tissue/min (median = 18.75). The calculated CO₂ reactivity ranged from –9.6 to 6.6% (median 1.1%) change in CBF/mm Hg change in PaCO₂. CO₂ reactivity correlated with lowest pH (r² = 0.35, p = 0.02). Two infants died, one of neonatal sepsis, the other of heart failure. Neurological outcome at the age of 1 year was normal in 11 patients, 1 had severe cerebral palsy. From the 12 surviving patients the patient with severe neurological deficit showed the highest CBF values (125.7 ml/100 g/min). Impaired chemical coupling of cerebral blood flow is compatible with intact neurological outcome in neonates with perinatal risk factors. CO₂ reactivity in these newborns correlates with the lowest pH and may reflect the severity of perinatal asphyxia.

Optical measurement of cerebral hemodynamics and oxygen metabolism in neonates with congenital heart defects

“…Our data agree with existing neonate data in the literature, 43,[73][74][75][76] but generally, these other studies measuring CO 2 reactivity were performed on other sick neonates with various clinical conditions, since it is ethically difficult to justify the use of methods requiring contrast agents or anesthesia to measure local CBF and also the artificial induction of hypercapnia. Thus, we are unable to compare our data to the responses of healthy neonates.…”

“…43,[73][74][75][76] Vascular reactivity to CO 2 was not found to depend on baseline CBF ASL-MRI or baseline PaCO 2 ͑p = 0.1 for both͒. The NIRS data was also in good agreement with previous NIRS studies on hypercapnia-induced changes in neonates.…”

Anatomy of the Circle of Willis and Blood Flow in the Brain-Feeding Vasculature in Prematurely Born Infants

“…The 133 Xenon inhalation is considered the gold standard method for CBF measurement [19,20] . The total CBF in neonates at term measured using 133 Xe method is in the range of 20-55 ml/100 g/min [19,21,22] . We found an overall mean total CBF of 104 ml/min, which is consistent with reported data assuming an average brain weight of 300 g [23] .…”

Cerebral blood‐flow velocities in predicting outcome of asphyxiated newborn infants

“…In infants with birth asphyxia, hyperperfusion is thought to be a sign of permanent brain damage with poor neurodevelopmental prognosis. The reason for this cerebral hyperaemia and low RI is thought to be severe vasoparalysis, a form of irreversible cerebral vascular injury (12,16,17). The severity of vasoparalysis and cerebral hyperaemia is thought to correlate with the degree of brain injury and presumably the severity of the asphyxial insult (12,16,17).…”

“…Several authors have reported high cerebral blood-flow (CBF) velocities and significantly lowered resistance indices (RI) in infants with severe hypoxicischaemic encephalopathy (HIE) at the age of 24-72 h (11)(12)(13)(14)(15). In infants with birth asphyxia, delayed hyperperfusion is thought to be a sign of permanent brain damage with poor neurodevelopmental outcome (12,16,17).…”