Effect of primary uterine inertia on blood gases and acid-base parameters in a chronically cannulated bovine foetus during calving: A case report

Foetal arterial catheterisation is an effective tool for conducting longitudinal in vivo studies on foetal blood gases and acid-base fluctuations. These surgical techniques have made obtaining daily blood samples under aseptic conditions feasible to determine arterial and/or venous blood gases and acid-base parameters. The present study aimed to elucidate the changes in arterial blood gases and acid-base variables obtained from a catheterised foetus during the final days preceding and during the calving process. It focused specifically on a case of primary uterine inertia and two typical cases. The average gestation length observed in three cows with chronically catheterised foetuses was 285 ± 10 days. The arterial and venous acid-base variables recorded in the three catheterised dams remained stable throughout the late gestation and calving phases. Similarly, these acid-base parameters remained consistent until the last 35 min before birth for Foetus B and until the last 22 min for Foetus A. At these points, physiological acidosis emerged in Foetus B, while moderate respiratory and metabolic acidosis developed in Foetus A until birth. In contrast, Foetus C experienced a gradual development of severe respiratory and metabolic acidosis during the last 8 h before birth, with continued deterioration observed in the 37 min leading up to birth. While there were no significant differences in the duration of electromyography (EMG) activities among the cows, a notable increase was recorded at 7 h before birth in Cow A and 15 h before birth in Cow B. Conversely, Cow C exhibited elevated EMG activity (>1,500 s*h-1) 8 h before birth. Additionally, during the last 3 h leading to birth in Cow C, a discernible reduction was noted compared to the other two cows. This case study highlights the importance of performing an exploratory vaginal examination when no clear clinical signs of stage one or any suspicious clinical symptoms, such as bloody vaginal mucus, are observed during the expected last day of gestation to prevent foetal mortality during calving.