Maternal Caffeine Administration and Cerebral Oxygenation in Near-Term Fetal Sheep

Abstract

The authors test the null hypothesis that maternal caffeine administration will not significantly alter fetal cerebral oxygenation. The authors measured fetal arterial blood gases, cortical tissue O₂ tension (tPO₂), sagittal sinus blood gases, and laser Doppler cerebral blood flow in response to a 30-minute caffeine infusion (400 mg intravenously) into 7 near-term pregnant ewes, and they calculated fractional O₂ extraction and relative cerebral metabolic rate for O₂ (CMRO₂). Following maternal caffeine infusion, both fetal cortical tPO₂ and sagittal sinus (HbO₂) decreased significantly, from 10.7 ± 0.9 to 6.8 ± 1.1 Torr and from 46% ± 2% to 37% ± 6%, respectively. This was associated with significant 20% to 30% increases in fractional O₂ extraction and CMRO ₂. Fetal arterial blood gas values did not change significantly. In conclusion, maternal caffeine administration significantly decreases cerebral oxygenation without affecting systemic oxygenation in fetal sheep. The authors speculate that for a fetus that may be otherwise compromised, this increase in CMRO₂ with decreased cortical tPO₂ could present a problem.