Abstract
Fetal (F) and placental (P) oxygen consumption (VO2) were calculated using continuous indirect calorimetry in 6 awake gravidas not in labor at 38 wks gestation with 6 AGA fetuses undergoing elective cesarean section utilizing complete lumbar epidural analgesia. Maternal (M) steady state was judged by stability of minute ventilation, MVO2, and percent carbon dioxide in expired air. Readings were obtained 10 min before delivery, 5–10 min after cord clamping, and 10–20 min after placental removal. Blood samples were obtained from umbilical vein (γ) and artery (α) for oxygen content (O2). A trimmed, drained P weight was obtained within 30 min of delivery. MVO2 decreased after cord clamping (FVO2), and still further after placental removal (PVO2). Fetal umbilical blood flow (f) was calculated from the Fick equation by solving for f=FVO2/([O2]γ – [O2]α).
These data agree favorably with measurements of FVO2, PVO2, and f in other mammalian species. Some of the variability in f is accounted for by one baby whose f=338 ml/min/kg, FVO2 = 13.0 ml/min/kg, and whose F/P=11.0. We speculate that babies attached to small placentas relative to their body size may have a higher metabolic rate during cesarean section than babies attached to large placentas relative to their body size.
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Bonds, D., Crosby, L., Cheek, T. et al. 241 HUMAN FETAL UMBILICAL BLOOD FLOW ESTIMATION BY APPLICATION OF THE BOHR PRINCIPLE. Pediatr Res 19, 151 (1985). https://doi.org/10.1203/00006450-198504000-00271
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DOI: https://doi.org/10.1203/00006450-198504000-00271
