When is regurgitus most likely to occur in horses?

Regurgitation in horses is most likely to occur at light or deep planes of anesthesia due to several factors related to the physiological changes that happen during these states. When a horse is under anesthesia, muscle tone is decreased, including the muscles that control the esophagus and stomach. At light planes, the animal may still have a lack of coordination and control, which can impede normal swallowing and increase the risk of regurgitation.

Deep anesthesia can also lead to airway reflexes being suppressed, reducing protective mechanisms that typically prevent aspiration. The combination of a relaxed esophageal sphincter and diminished gag reflex contributes to a higher risk of regurgitation during these planes of anesthesia. This physiological understanding highlights the critical monitoring that must be in place during anesthesia in horses to prevent complications like this from occurring.

While heavy sedation may pose some risk, it does not carry the same likelihood as the anesthesia levels mentioned. Being fully awake and active typically allows for normal physiological function in terms of swallowing and respiratory control, reducing the risk of regurgitation. Post-operative recovery can present its own challenges, but the specific concern of regurgitation is not as prevalent as during anesthesia.