Rabbit analgesia

We’re all used to giving dogs and cats pain relief pre and post-surgery, as well as for chronic conditions such as arthritis, but how often do we think about our rabbit patients.

Posted: 29 May 2019

Rabbit analgesia

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The answer is probably more than we used to, but we could still be doing more, particularly as there have been numerous studies over the years to show that analgesia in rabbits is often inadequate.

Part of the problem arises because the assessment of pain in rabbits can be difficult and challenging. As a prey species they are masters at hiding the signs of pain, so we have to watch carefully and know what we are looking for.

What is pain?

Pain has been defined as ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage’.

When should be using pain relief?

There are all sorts of painful procedures and conditions in rabbits which would benefit from intervention with analgesia. Some typical examples we might see include;

  • Neutering - spay/ovariohysterectomy and castration operations
  • Fight wounds
  • Dental treatment
  • Gastrointestinal diseases
  • Surgical treatment of abscesses and tumours
  • Orthopaedic procedures
  • Urinary problems
  • Caesarean section
  • Laparotomy

How do you recognise pain?

As we’ve already mentioned, recognising pain in prey species can be difficult, and in rabbits it can be affected by a number of variables. For example, you need to take into account;

  • The individual – some animals are more stoic than others
  • Animal’s age – the very young and very old are more likely to show pain
  • Subjectivity – each individual vet/nurse/owner might assess pain differently
  • Other conditions – infections, stress and dehydration may mask pain

Subtle behavioural changes

Knowing what is normal will help, since slight variations from the norm may be all that you can find to know the animal is experiencing pain. Some examples include;

A reduction in;

  • Activity or interest in exploring
  • Appetite and weight
  • Faecal pellets

Or an increase in;

  • Heart and respiratory rate
  • Flinching or licking wounds

Other pointers of pain include;

  • Hunched posture
  • Abdominal straining
  • Teeth grinding
  • Saliva drooling
  • Sitting quietly
  • Eyes half-closed

The Grimace Scale

We’ve been using qualitative and quantitative measurements of pain for years in other species, and the ‘Grimace scale’ is just one example of a pain assessment guide. The idea is to look at the animal carefully and take note of small changes in facial expression, all of which help you to quantify pain. The specific facial features change according to the level of the pain. Some facial indicators include;

  • Orbital tightening
  • Cheek flattening
  • Nose and nostril shape
  • Whisker position
  • Ear position

Have you seen Newcastle University’s Rabbit Grimace Scale?

Giving pain relief

Perioperative analgesia

We are increasingly aware of the need to give analgesics prior to and after surgery. By doing this you’ll reduce the dose and risks from anaesthesia, as well as minimise any complications during the recovery period as a result of pain and stress (e.g. gut stasis). It can’t be stressed enough how important it is to give effective pain relief to rabbits when considering surgery.

Non-pharmaceutical help

Whilst underused, there are still opportunities and situations when drug free pain relief can be used. This might involve the use of;

  • Cold and heat therapy
  • Laser treatment
  • Physiotherapy
  • Acupuncture
  • Massage

Pharmaceutical approach

The three main groups of analgesics available to us in the UK are opiates, nonsteroidal anti-inflammatory drugs (NSAID’s) and local anaesthetics. These can be used alone or in combination.

1. Opiates

Now widely used, these produce both central and peripheral pain relief. They are generally safe, versatile and often reversible. The most frequently used opiates are the synthetic partial agonists, buprenorphine and butorphanol.

Butorphanol is around 5 times as potent as morphine, whilst buprenorphine is even more effective, being around 30 times stronger. They can both be dosed to effect and importantly, don’t cause significant CNS depression.

Side effects are generally only seen when an animal receives an overdose, which could result in;

  • Drowsiness
  • Bradycardia
  • Hypothermia
  • Respiratory depression
  • Drop in arterial oxygen
  • Reduced gastrointestinal motility
  • Decreased arterial blood pressure

Opiates used in rabbits

  • Buprenorphine – this is probably the most commonly used opiate in rabbits. It can be given orally or by injection (iv/im and sc). It’s duration of action is between 6–10 hours.
  • Butorphanol – this would be used for mild to moderate pain. It has a relatively short duration of action, lasting around 2 – 4 hours.
  • Fentanyl – this is used in combination with fluanisone and is sold as Hypnorm. Be aware that it can be antagonised by butorphanol and buprenorphine.
  • Tramadol – whilst not licenced for use in rabbits, it is used to treat mild, acute and chronic pain.

2. Non-steroidal anti-inflammatory drugs (NSAID’s)

This group of drugs is widely used in small animal and exotic practice. They not only have analgesic properties, but also anti-inflammatory and antipyretic effects. You have to be cautious when using them though as they are contraindicated with;

  • Renal diseases
  • Hepatic disease
  • Gastrointestinal ulcerations
  • Reduced organ perfusion

The most frequently used NSAID’s in rabbits are meloxicam and carprofen.

  • Carprofen – this is used for mild, moderate, acute and chronic pain
  • Meloxicam – suitable for the treatment of various forms of chronic pain

3. Local anaesthetics

These work by blocking the transmission of a painful stimulation to the central nervous system. A common local anaesthetic used in rabbits is EMLA cream (a mix of prilocaine and lidocaine). EMLA cream is frequently used for placement of intravenous catheters.

Other local anaesthetics include lidocaine and bupivacaine, which are used for;

  • Local infiltration
  • Nerve blocks for dental extraction
  • Intra-testicular placement prior to castration
  • Epidural analgesia

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