Domestic ruminants have a large rumen that is usually full of liquified materials and it does not empty completely even after a period of fasting. These animals are susceptible to complications associated with recumbency and anesthesia.
Speaking at the 2012 Western Veterinary Conference last week, Hui-Chu Lin, DVM, MS, Dipl. ACVA, Auburn University, said tympany, bloat, regurgitation, and aspiration pneumonia are common problems that should be anticipated and addressed with proper precautions. “When possible, adult animals should be fasted for 24 to 48 hours and water withheld for 24 hours before induction of anesthesia. Fasting of neonates is not recommended because of the potential for hypoglycemia and prolonged recovery.”
Lin noted that fasting may not be possible under emergency situations and precautions should be taken to avoid aspiration of gastric fluid and ingesta. Prevention of regurgitation and aspiration of ruminal content can be done effectively by placing the animal in sterna recumbency and endotracheal intubation institute immediately following induction.
However, some practices may induce anesthesia with animal already strapped to the table and in lateral recumbency. “Thus, it is even more important to ensure animals are under adequate plane of anesthesia to prevent stimulation of active regurgitation and allow immediate intubation,” Lin explained. “Positioning of the head so that the throat latch area is elevated relative to the mouth and thoracic inlet will help draining and prevent pooling of the saliva and ruminal contents in the oral cavity.”