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

Abstract

Objective: Evaluate the association between carbon dioxide (pCO2), cerebral blood flow (CBF), and cerebral autoregulation (CA) in preterm infants. Study design: Cerebral saturations (rScO2, surrogate for CBF using NIRS) and mean arterial blood pressure (MAP) monitored for 96 h in infants <29 weeks gestation. Relationship between rScO2, the rScO2-MAP correlation (CA analysis) and pCO2 category assessed by mixed effects modeling. Results: Median pCO2 differed by postnatal day (p < 0.0001)—pCO2 increased between day 1 and 2, and low variability seen on day 4. A 5% increase in rScO2 was noted when pCO2 was >55 mmHg on each postnatal day (p < 0.001). No association observed between the overall rScO2-MAP correlation and pCO2. On day 1 only, the correlation coefficient decreased from 0.26 to −0.09 as pCO2 category increased (p = 0.02). Conclusions: CBF increased above a pCO2 threshold of 55 mmHg, but overall, no association between pCO2 and CA was noted.