The use of intravascular catheters for long-term studies on the mare and fetus.

This research explored techniques for inserting catheters into the umbilical artery, uterine vein, and umbilical vein of pregnant horses, with the aim of investigating various aspects of placental exchange and hormonal conditions of the fetus.

Research Goals

• The main aim of the research was to develop a method for the long-term intravascular catheterization of the umbilical artery, vein, and uterine vein in pregnant mares. The researchers sought to maintain these catheters for enough time to scrutinise placental exchange and hormonal conditions within the fetus.

Catheterization Techniques

• The methods used for inserting these catheters required careful anesthesia to prevent the mares and their fetuses from experiencing discomfort or distress.
• The team also needed to maintain normal blood gas tensions, pH, and arterial blood pressure throughout the process to ensure the wellbeing of the mares and their fetuses.

Fetal Survival

• There were variable survival rates among the fetuses. Despite employing anesthesia and precautionary measures, some fetuses did not survive.
• Among the surviving cases, three mares delivered live foals, and six foals survived for over 15 days in the womb post-operation, with the longest survival period recorded at 41 days.

Significance of Erythrocyte Sedimentation Rate (ESR)

• The researchers noticed that the ESR of the fetal foal was consistently low immediately after the operation, but it slowly increased thereafter.
• A sudden large rise in the ESR often signaled impending fetal death, making this measure a potential indicator of fetal health post-catheterization.

Unexplained Fetal Deaths

• Despite the research team’s efforts, the sudden in-utero deaths of some fetuses catheterized and maintained for ten days or more could not be explained, indicating that this is a complex and delicate area of study with various contributing factors.

Implications and Conclusions

• Despite the aforementioned challenges, the research showed that it is possible to maintain relatively stable and long-lasting catheter preparations in the uterine vein and umbilical artery and vein of pregnant horses. This allows for investigation into the placental exchange and endocrine climate of the fetus, opening up potential avenues for future research.