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

Objective: Evaluate the association between carbon dioxide (pCO), cerebral blood flow (CBF), and cerebral autoregulation (CA) in preterm infants.

Study Design: Cerebral saturations (rScO surrogate for CBF using NIRS) and mean arterial blood pressure (MAP) monitored for 96 h in infants <29 weeks gestation. Relationship between rScO, the rScO-MAP correlation (CA analysis) and pCO category assessed by mixed effects modeling.

Results: Median pCO differed by postnatal day (p < 0.0001)-pCO increased between day 1 and 2, and low variability seen on day 4. A 5% increase in rScO was noted when pCO was >55 mmHg on each postnatal day (p < 0.001). No association observed between the overall rScO-MAP correlation and pCO. On day 1 only, the correlation coefficient decreased from 0.26 to -0.09 as pCO category increased (p = 0.02).

Conclusions: CBF increased above a pCO threshold of 55 mmHg, but overall, no association between pCO and CA was noted.