Post-operative analgesia

Liverpool, United Kingdom

In recent decades, significant advancements have taken place in modern equine anaesthesia, medicine and surgery, leading to highly sophisticated treatments and surgical techniques. Despite these notable advances, including the adoption of balanced anaesthesia protocols, multimodal analgesia, standing surgery, and minimally invasive techniques, specific surgical procedures unavoidably give rise to varying degrees of moderate to severe pain. Minimising pain in the peri-operative period remains pivotal to ensure animal welfare and promoting enhanced recovery, ultimately yielding improved treatment outcomes. However, effectively mitigating pain requires the ability to accurately identify it, which can present a more significant challenge (van Loon & Van Dierendonck, 2018).

The International Association for the Study of Pain (IASP) updated the definition of pain in 2020. The IASP defines pain as an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage (Raja et al., 2020). Adding to this definition, six key notes were introduced by the IASP. The most relevant to the study of pain in animals was the recognition that verbal description is only one of several behaviours to express pain; inability to communicate does not negate the possibility that a human or a nonhuman animal experiences pain (Raja et al., 2020).

Pain assessment in humans benefits from their capacity to convey pain-related attributes such as quality, location, and intensity verbally. However, the utilisation of self-report is infeasible for pain assessment in horses. As a result, the evaluation and quantification of pain in horses and other animals rely upon the observer’s capacity in discerning potential pain-associated alterations in both behavioural patterns and physiological parameters exhibited by the patient. In order to optimise the objectivity and consistency of pain assessment, it becomes imperative to undertake the following steps:

• Determine the specific behaviours and physiological parameters that may be indicative of pain.
• Systematise the observation of these indicative signs.
• Delineate the degree of pain correlation with specific behavioural manifestations.
• Integrate these empirical observations into a quantitative metric, facilitating the estimation of pain intensity over time.

This comprehensive approach aids in determining the potential requirement for analgesic intervention and enables the detection of treatment efficacy. The drive for objective pain assessment prompted the development of systematic evaluation through pain scales. These scoring systems must undergo validation tailored to the specific type of pain, considering factors like condition and duration (e.g., acute post-abdominal surgery).

When a horse is identified as being in pain or likely to experience pain following a surgical procedure, a well-structured pain management plan is essential. An effective analgesic plan includes a combination of systematically administered drugs along with locoregional analgesic techniques when feasible. The key lies in understanding the nature of potential pain, drug mechanisms, and their application to optimise pain relief (Elvir-Lazo & White, 2010). This approach results in a multimodal therapeutic plan that combines appropriate drugs and targets various aspects of the pain pathway. Common systemic administration routes involve intravenous or intramuscular injections for short-term relief, while oral medication is employed for more extended treatment periods. Although a combination of these routes is usually sufficient, alternative methods of drug delivery, such as transdermal, oral-transmucosal, epidurally or intra-articular can enhance analgesia for specific cases. When managing post-operative pain in horses, it is essential to formulate a “pain ladder” approach. This entails creating an individualised pain management plan that remains adaptable and follows a continuous cycle of plan–treat–evaluate. Cautiously monitoring the patient’s response is integral for a successful post-operative pain management protocol.

Supplementary therapies, such as pharmacological and non-pharmacological methods to reduce stress during hospitalisation, along with practices like bandaging, attentive nursing, physiotherapy, farriery, and specific surgical interventions, are essential contributors to attaining positive outcomes in post-operative pain management.

The aim of this presentation is to present current evidence, examining both the benefits and obstacles of utilising pain scales in horses. Additionally, I will explore various pharmacological and non-pharmacological methods for pain management in horses during the post-operative period. The intent of this analysis is to initiate a dialogue regarding the compelling requirement for enhanced pain relief in equine care.