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.