Nerve blocks are one of the most dangerous procedures for equine veterinarians to perform, putting them at significantly increased risk of fracture, concussion, head injury, and hospitalization. To make nerve blocks safer to perform, the first step is to make the horse feel safer in that scenario.
Gemma Pearson, BVMS, CertAVP(EM), MScR, CCAB, PhD, FRCVS, Director of Equine Behaviour at The Horse Trust and Lecturer in Equine Behavioural Medicine at the University of Edinburgh’s Royal (Dick) School of Veterinary Studies, provided learning-theory-based recommendations during a presentation at the 2025 British Equine Veterinary Association Congress.
“We should remember that when horses react in a dangerous manner, this is a normal response to an acute stressor for this species—they are just trying to keep themselves safe—as they lack the capacity to understand our intentions,” she explained.
The Use (and Misuse) of Restraint
The advice we often hear to reduce risk around horses is to ensure the animal is appropriately restrained. But what is “appropriate restraint”?
“There is a ‘Goldilocks’ level of restraint that makes it as safe as possible for you, whereby you have control of the horse without increasing its level of arousal,” said Pearson.
Too little restraint, and the horse might move away from the block or kick or trample the veterinarian. Too much restraint, and the horse might become scared, uncomfortable, and dangerous.
“Restraint is inherently aversive to horses,” she added. “So when we put too much restraint on them, it can actually be more aversive than the nerve blocking scenario.”
While restraint is an important part of staying safe, Pearson advised putting more emphasis on keeping the horse’s level of arousal low than on physical restraint.
Lowering the Boiling Point
Equine behaviors that can cause veterinarians injury are normal responses to acute stressors.
“We need to look at the horse in front of us and their level of arousal,” said Pearson. “When it gets to a boiling point is when things are going to start to go wrong. That’s going to look different for different individual horses.”
Some horses’ behavioral responses to stressors are proactive (fidget, flight, fight), while others are reactive (freeze). “I think the freeze response is one vets often get injured by because the horse is standing still, and they don’t realize its ‘temperature’ is increasing until it explodes,” she added.
To lower the horse’s arousal level, you can use learning theory and minimally invasive approaches, including:
- Gentle techniques.
- Accurate needle size and placement.
- A comfortable position for the horse and the least amount of restraint that’s still effective.
- A skin bleb of local anesthesia.
- A topical cream to reduce skin sensation for more sensitive horses.
For challenging horses, Pearson recommended taking the time to perform classical counterconditioning: “This is where we teach the horse to associate someone touching their leg with a positive outcome (usually food) rather than the discomfort that might be associated with a needle. Then when we do insert the needle, the horse is thinking about the food and is in a positive mood state, so finds it less aversive.”
To further reduce the horse’s stress response, try to minimize noise and distractions in the exam room. The next level of learning theory is operant conditioning (e.g., clicker training), but it requires more skill to get the timing just right and might take a day or two to retrain the horse, said Pearson.
Pharmacological Help
You might consider administering drugs when:
- The horse’s arousal level is beyond the threshold before you even begin.
- You don’t have time.
- To make a situation safer and less stressful.
Options to lower that level of arousal include acepromazine, trazodone, and alpha-2 agonists like Xylazine. Pearson reminded veterinarians that acepromazine has a negative effect on how the horse feels (depressed), while trazodone has a positive impact (content, relaxed).
Final Considerations
Each horse is an individual, and you must think about many factors when assessing a horse’s likelihood of reacting to a nerve block and to what degree. Nonhorse factors Pearson listed include:
- Type of block (e.g., forelimb vs. hind limb, which is typically more aversive; palmar digital vs. deep branch lateral plantar block).
- The veterinarian’s technical experience.
- The vet’s impact on horse arousal, as some individuals are more calming or aversive than others.
- The vet’s confidence in their ability to perform an accurate nerve block.
- The handler.
Horse factors include:
- Age, as young horses often have higher arousal.
- Athleticism and increased sensitivity.
- Stress.
- Chronic pain, which can cause the horse to be more sensitive.
- Poor training or can’t stand still.
- The suspected number of blocks you’ll be performing.
At the end of the day, said Pearson, we need to focus on helping the horse feel safe if we want to keep ourselves safe.
Related Reading
- Injury Risk and Prevalence in Equine Practice
- Combining Xylazine and Lidocaine for Longer-Acting Nerve Blocks
- Disease Du Jour: Diagnostic Anesthesia in Equine Lameness Exams
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