Hypoxic-Ischemic Encephalopathy: Cerebrovascular Carbon Dioxide Reactivity in Neonates

ABSTRACT

Using noninvasive measurement of cranial blood flow, we previously demonstrated that full-term asphyxiated neonates have decreased cerebral perfusion that can persist up to 5 days of age. In an attempt to test their postischemic cerebrovascular CO₂ reactivity, we measured cranial blood flow in ten asphyxiated term (39 ± 0.8 weeks and 3078 K 400 gm) infants with and without inhaled carbon dioxide (3 percent). The end tidal CO₂ (PaCO₂) increased significantly, from 28.8 ±1.0 mm Hg to 32.3 ± 2.0 mm Hg after CO₂ inhalation (p < 0.01), whereas the cranial blood flow showed no significant change (38.5 ± 5.0 ml/min/100 gm brain weight to 37.6 ± 6.0 ml/min/100 gm brain weight). We conclude that term infants with hypoxic-ischemic encephalopathy have low cranial blood flow at 3 days of age. Their cerebrovascular response to inhaled CO₂ is variable and suggests some impairment.