Transcutaneous and Arterial Carbon Dioxide Tension at Various Conditions of Fetal Stress in Lambs

Abstract

In an acute fetal lamb model the relation between arterial PCO₂ (PaCO₂), transcutaneous PCO₂ (tcPCO₂) and pH was studied at different conditions of stress. Occlusion of the maternal common iliac artery for 8 min, umbilical cord obstruction for 5 min and placental embolization were performed subsequently, every time with an interval of 1 h for fetal recuperation. During the first 2 experiments arterial values changed rapidly after occlusion and returned nearly to normal within 30-60 min after the end of occlusion. TcPCO₂ started to increase several minutes after occlusion and reached its maximum about 5 min after the end of occlusion. Afterwards a gradual decrease towards the onset value was observed. During placental embolization tcPCO₂ did not increase until 15 min before fetal death. It is concluded that tcPCO₂ can follow a gradual trend, but not quick changes in PaCO₂.

Transcutaneous and Arterial Carbon Dioxide Tension during Intermittent Umbilical Cord Occlusion in Fetal Sheep

“…In an animal experiment, tcPco? followed changes in PaCCT during various conditions of fetal stress, but with a substantial delay [ 17], It remains unclear however to what extent tcPco? reflects the actual intravascular acid-base balance during labor, especially when fetal acidosis devel ops gradually as a result of intermittent uterine contrac tions, interfering with uterine blood flow and umbilical cord circulation.…”