Prolongation of anesthesia with xylazine, ketamine, and guaifenesin in horses: 64 cases (1986-1989).

The study explores the efficacy of prolonging anesthesia in horses using xylazine, ketamine, and guaifenesin. The method was applied to 74 occasions, involving 54 horses and 6 foals. Overall, the results showed consistent and stable vital signs, however, the time for the horses to regain their standing posture was longer when two extra injections were applied during anesthetic procedure.

Methodology and Participants

• During the course of the study, 54 horses and 6 foals were anesthetized on total of 74 occasions. The anesthetic agents used were xylazine and ketamine, or xylazine, guaifenesin, and ketamine with, or without butorphanol.
• The anesthetic was prolonged on 64 occasions by administering 1 to 9 additional IV injections of xylazine and ketamine, at roughly third the initial dosage. This extension lasted for up to 70 minutes with an average duration of 34 +/- 15 minutes.
• All horses, excluding 5, were placed in lateral recumbency, and subjected to oxygen insufflation.

Anesthetic Procedure and Timing

• In adult horses, the time from anesthesia induction to the first supplemental xylazine and ketamine injection was approximately 13 +/- 4 minutes.
• The time period between these supplemental injections was estimated to be around 12.1 +/- 3.7 minutes.
• This data was found to be in harmony with predicted plasma ketamine concentration derived from previous pharmacokinetic studies on ketamine usage in horses.

Physiological Responses

• The horses’ vital functions such as respiratory and heart rates, along with coccygeal artery pressure, remained stable throughout the duration of anesthesia.
• The time between the last ketamine injection and when the horse assumed a sternal position was roughly 30 minutes, regardless of the number of supplemental injections.
• The time required for the horses to stand was noticeably longer (P less than 0.05) in cases when two additional injections were given, in comparison to those not given any or given only one supplement. However, this prolonging effect did not occur in horses given three extra injections.

Recovery Observations

• Despite the anesthetic extension, the recovery process was unsatisfactory in only 5 horses. There was not an observable relationship between the extension of anesthesia and the quality of recovery, indicating that the procedure did not significantly affect their post-anesthetic conditions.