The association between carbon dioxide, cerebral blood flow, and autoregulation in the premature infant

OBJECTIVE: Evaluate the association between carbon dioxide (pCO(2)), cerebral blood flow (CBF), and cerebral autoregulation (CA) in preterm infants. STUDY DESIGN: Cerebral saturations (rScO(2,) surrogate for CBF using NIRS) and mean arterial blood pressure (MAP) monitored for 96 h in infants <29 weeks gestation. Relationship between rScO(2), the rScO(2)-MAP correlation (CA analysis) and pCO(2) category assessed by mixed effects modeling. RESULTS: Median pCO(2) differed by postnatal day (p < 0.0001)—pCO(2) increased between day 1 and 2, and low variability seen on day 4. A 5% increase in rScO(2) was noted when pCO(2) was >55 mmHg on each postnatal day (p < 0.001). No association observed between the overall rScO(2)-MAP correlation and pCO(2). On day 1 only, the correlation coefficient decreased from 0.26 to −0.09 as pCO(2) category increased (p = 0.02). CONCLUSIONS: CBF increased above a pCO(2) threshold of 55 mmHg, but overall, no association between pCO(2) and CA was noted.