Acute anemic hypoxemia produces a transient depression in fetal respiratory activity.
Isovolemic anemia was produced in 11 unanesthetized fetal sheep by withdrawal of blood and replacement with saline-dextran. Fetal hematocrit fell from 36 +/- 1 to 19 +/- 1% (SE). Fetal breathing movements, which were present during 34.4 +/- 5.5% of 3 h before the anemia, occurred 10.1 +/- 5.3, 14.8 +/- 4.4, and 27.1 +/- 6.7% in the 3 h following. The anemia caused a fall in arterial O2 concentration from 8.4 +/- 0.3 to 3.6 +/- 0.1 vol% and sagittal vein PO2 fell from 15.4 +/- 0.5 to 12.4 +/- 0.3 Torr. Cerebral metabolic rate during the period of anemia was 2.9 +/- 0.1 ml.100 g-1.min-1, which was unchanged from the control value of 3.0 +/- 0.2 ml.100 g-1.min-1. Sagittal vein PCO2 (54.2 +/- 1.4 Torr) remained constant after the fetus was made anemic. We conclude that respiratory activity in the sheep fetus is depressed by anemic hypoxemia but that the effect is transient.
D000818:Animals; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation; D004569:Electroencephalography; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000502:physiology*; D006400:Hematocrit; D010100:Oxygen / Q000097:blood*; D011247:Pregnancy; D012119:Respiration; D012756:Sheep
D002245:Carbon Dioxide; D010100:Oxygen