Locoregional anaesthesia for surgical procedures

It is well-documented that the risk of anaesthesia-related mortality in horses is considerably higher compared to dogs, cats, and humans. The preliminary findings from CEPEF-4 reported a mortality rate of 0.2% related to standing sedation in horses, in comparison to a 1% mortality rate for horses undergoing general anaesthesia (Gozalo-Marcilla et al., 2021). As anticipated, the occurrence of fatalities linked to standing sedation appears to be lower than that associated with general anaesthesia, highlighting the fact that standing sedation eliminates the mortality risk associated with recovery from general anaesthesia.

As a result, there’s a growing interest in performing surgery under standing sedation (Loomes & Louro, 2023) . This, along with a stronger focus on improving pain management in horses, has sparked a greater enthusiasm for exploring and thoughtfully assess a range of both pioneer and well-established techniques of locoregional anaesthesia and analgesia techniques in equine anaesthesia. However, the benefits of locoregional anaesthesia and analgesia extend beyond horses undergoing surgery under standing sedation. These approaches also offer numerous advantages for horses undergoing surgical procedures under general anaesthesia, including pre-emptive analgesia, reduced general anaesthetic requirements resulting in decreased drug side effects, improved recovery quality and post-operative pain relief (Gaesser et al., 2020; Louro et al., 2020).

Traditional perineural blocks in equine veterinary medicine have historically been performed blindly guided by anatomical landmarks. While this method can be effective through direct nerve palpation, its practicality is limited to nerves located close to the skin’s surface. Recent years have witnessed a surge in research in human and small animal anaesthesia due to the adoption of innovative approaches and technologies to locate nerves situated deeper to the skin, such as peripheral nerve stimulation and ultrasound-guided injections. These techniques have to potential to improve accuracy and precision, as well as reduce complications associated with regional anaesthesia and analgesia. The use of these objective methods for locoregional anaesthesia in equine patients has led to the development of various new techniques for targeting different nerves and desensitising various anatomical areas, allowing for standing surgery as well as reduced intraoperative pain during surgery performed under general anaesthesia. To assess the advantages and disadvantages of these objective methods in comparison to traditional blind locoregional anaesthetic techniques, and to determine their impact on equine anaesthesia, analgesia, and surgery, further research is necessary. Developing a thorough grasp of the effects of these objective methods of nerve location has the potential to greatly facilitate the incorporation of such techniques into the day-to-day procedures of equine veterinary surgeons. Consequently, this empowerment will equip clinicians to make informed choices when selecting the most appropriate locoregional approaches for their equine patients, ultimately resulting in better patient care standards and enhanced surgical results.

Various drugs are used to perform locoregional anaesthesia or analgesia in horses. Among these, local anaesthetics are the prevailing choice, although additional drug categories such as opioids and alpha-2 adrenoceptor agonists can also be administered to achieve analgesia via locoregional methods. Recentadvancements in pharmacology have endeavoured to influence the pharmacokinetics of local anaesthetics, aiming to prolong the duration of action of the block. This has been pursued through techniques such as encapsulating local anaesthetics within liposome molecular structures or introducing additives to traditional local anaesthetics.

This presentation purposes to present existing literature, discussing the advantages and disadvantages of performing locoregional anaesthesia and analgesia in horses undergoing surgical procedures either under general anaesthesia or standing sedation. This analysis aims to stimulate discussion on the utility and potential future of locoregional anaesthesia for equine patients.