Modified Ruminal Management in Ovine Preclinical Anesthesia: Eliminating Oro-Ruminal Intubation to Reduce Complications

Presenter: Caroline Baldo, Boston Scientific

Introduction: In small ruminants undergoing general anesthesia (>1.5 hours), ruminoreticulum dilation can occur secondary to gas and/or fluid accumulation. Oro-ruminal intubation is controversial due to the potential risks outweighing the perceived benefits. The tube normally sits in the fluid layer draining ruminal content, disrupting flora and predisposing to pathologies such as ruminal acidosis. Trauma is another risk, however, equally important is the forced opening of the lower esophageal sphincter which disrupts the pressure barrier, predisposing to ruminal content drainage. Copious amounts of content in the oral cavity are often noticed increasing the risk of aspiration pneumonia. Herein, the modification of ruminal management in preclinical ovine.

Methods: Three sheep were managed with oro-ruminal tubes placed after endotracheal intubation. Post-operatively, two developed severe ruminal acidosis culminating in euthanasia, and one developed pneumonia. These complications prompted revisiting ruminal tube placement as this is uncommon in clinical veterinary anesthesia. Initiating in November 2024, all ovine at our test facility undergoing general anesthesia (approximately 18 subjects, procedures < 6 hours) were managed without oro-ruminal intubation. Proper animal positioning, continuous oral suction, and post-operative dietary changes were updated. Anesthesia medications were unchanged and pain monitored with the UNESP Botucatu composite pain scale for ovine. A sling was used for recovery.

Results: All animals remained stable throughout: no adverse cardiopulmonary or the gastrointestinal events were noted intra- or post-operatively. None of the animals needed trocarisation at any time. Abdominal circumference was larger in procedures lasting >4 hours with increased eructation in recovery. Ruminal contents in the oral cavity and on the operating table were reported but perceived to be less than animals with an oro-ruminal tube.

Conclusion: In procedures up to 6 hours, no adverse events were reported. Ruminal dilation was observed but can easily be prevented or treated by placing a pressure relief valve*. Overall, the abandonment of the oro-ruminal tube along with proper fasting, post-operative diet management, endotracheal intubation, ideal patient positioning, diligent monitoring and species-specific recovery techniques are key to successful outcomes.
* A Foley or urinary catheter with a distal cuff is inserted through a vascular sheath placed percutaneously in the left sub-lumbar fossa and into the rumen. A three-way stopcock is attached to the Foley or urinary catheter and opened to release gas at any time.