Comparison of xylazine-ketamine-guaifenesin and xylazine-tiletamine-zolazepam protocols for constant rate infusion anesthesia in horses undergoing field castration.

Overview

• This study evaluated and compared two anesthesia protocols for horses undergoing castration in the field: the traditional xylazine-ketamine-guaifenesin (XKG) “triple drip” and an alternative xylazine-tiletamine-zolazepam (XTZ) protocol.
• The study found that the XTZ protocol provided similar anesthetic effectiveness and cardiorespiratory stability to the classical XKG protocol, suggesting XTZ could be a viable alternative where ketamine and guaifenesin use is restricted.

Background and Rationale

• Constant rate infusion (CRI) anesthesia using a combination of drugs is common in equine surgeries, particularly in field conditions where equipment and facilities are limited.
• The “triple drip” protocol—xylazine, ketamine, and guaifenesin (XKG)—is widely used for maintaining surgical anesthesia because of its balanced effects and safety profile.
• However, many countries impose legal restrictions on the use of ketamine and guaifenesin, limiting the use of the standard triple drip approach.
• Tiletamine-zolazepam (TZ), a combination of dissociative anesthetic and benzodiazepine, is a potential alternative anesthetic agent that could replace ketamine and guaifenesin in CRI protocols.
• Prior to this study, limited research had assessed how well xylazine combined with TZ (XTZ) worked for CRI anesthesia in equines in field settings.

Study Objective

• The main goal was to compare the anesthetic effectiveness and safety of the XTZ protocol against the classical XKG triple drip protocol in horses undergoing field castration.

Methods

• Twelve healthy stallions were randomly assigned to one of two groups (6 horses per group): XKG or XTZ.
• All horses were premedicated with intravenous xylazine at 1 mg/kg to induce sedation.
• For induction:
• XKG group received ketamine 2 mg/kg IV.
• XTZ group received tiletamine-zolazepam (TZ) 1 mg/kg IV.
• For maintenance anesthesia via CRI:
• XKG group: xylazine 1.375 mg/kg/h, ketamine 2.75 mg/kg/h, guaifenesin 68.75 mg/kg/h.
• XTZ group: xylazine 0.75 mg/kg/h, tiletamine-zolazepam 1.5 mg/kg/h.
• Parameters measured included anesthetic depth and cardiorespiratory functions to assess safety and effectiveness.

Results

• No clinically significant differences were observed between the two groups in terms of anesthetic effects.
• Cardiorespiratory parameters, such as heart rate, respiratory rate, and blood pressure, were comparable between XKG and XTZ protocols.
• This indicates that both protocols maintained stable anesthesia and vital signs during the surgical procedure.

Conclusions

• The tiletamine-zolazepam based CRI combined with xylazine (XTZ) effectively maintained anesthesia in horses undergoing castration in field conditions.
• The XTZ protocol may serve as a practical alternative to the classical triple drip (XKG), particularly in regions where ketamine and guaifenesin availability is restricted.
• This alternative could allow veterinarians greater flexibility in anesthetic protocols without compromising safety or efficacy during field surgeries.

Implications and Future Directions

• The study supports the adoption of XTZ CRI protocols for equine field anesthesia when traditional drugs are unavailable or restricted.
• Further larger-scale studies could confirm these findings and optimize dosing and administration protocols.
• Additional research into recovery quality, long-term safety, and applicability in other types of equine surgeries would help validate the broader use of XTZ.