Pain Types in Dogs
Behavioural Signs
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Posture
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Changes in behaviour
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Facial expressions
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Other
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• Hunched posture
• Guarding painful area
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• Withdrawn or uninterested in surroundings
• Aggressive
• Clingy
• Reluctance to move
• Restlessness
• Unusual licking or chewing at an area
• Reduced appetite
• Aversion to being touched
• Nausea
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• May have a ‘worried’ look above the eyes
• May look pinched around the mouth
• May show whites of eyes or make darting movements with eyes
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• Lameness or abnormal gait
• Vocalisation
• Muscle atrophy may occur if pain has been chronic
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Physiological
- Rapid breathing rate
- Rapid heart rate
- Elevated temperature
- Increased blood pressure
- Increased blood cortisol level
- Increased blood glucose levels
- Salivation
- Weight loss if pain has been chronic
Signs of Pain in Cats
Behavioural
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Posture
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Changes in behaviour
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Facial expressions
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• Hunched posture
• Tense muscles
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• Very quiet
• May stop grooming or start over-grooming
• Unwillingness to move
• Lameness or abnormal gait
• Muscle atrophy if pain has been chronic
• Appetite loss
• Hiding
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• Half closed or squinting eyes
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Physiological
- Rapid breathing rate
- Rapid heart rate
- Elevated temperature
- Increased blood pressure
- Increased blood cortisol level
- Increased blood glucose levels
- Salivation
- Weight loss if pain has been chronic
Common Techniques Nurses May Use to Manage Pain
- Provide clean, dry and comfortable bedding at all times
- Keep the patient clean and dry
- Gentle handling when moving the patient
- Patting and talking to the patient
- Massage may be beneficial; check this with the vet
- Toys or bedding from home
- Cats may like a box to hide in or part of the cage door covered for privacy
- Provide a quiet environment
- Provide warmth, either localised (e.g., covered hot water bottle) or general (heated room)
- Keep out of draughts
- Minimal disturbance (e.g., do TPR when medicating)
- Don’t wake sleeping patients
- Regular toilet walks if the patient’s condition allows
- Rotate the patient at least 4 times daily if they are unable to turn themselves
- Assess wounds and bandages regularly
- Assess pain levels regularly and discuss the patient’s condition with the vet
Pain Scoring
Simple unit-dimensional scale
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Type of unidimensional scale
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Description of scale
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Advantages
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Disadvantages
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Simple descriptive scale (SDS)
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3- or 5-point scale where scorer assigns a description based upon their own unstructured assessment of the animal; e.g., no pain/mild pain/moderate pain/severe pain
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Very simple to use and understand
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• Not validated
• Non-linear
• Definitions of the descriptive words are open to interpretation (very subjective)
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Numerical rating scale (NRS)
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A score from 0 to 10 is given based upon scorer’s own unstructured assessment of the animal, with 0 being no pain and 10 being the maximum pain possible
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• Simple to use
• More sensitive and reliable than SDS or VAS
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• Not validated
• Non-linear (e.g., animal with a score of 8 is not necessarily four times as painful as one with a score of 2)
• Subjective
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Visual analogue scale (VAS)
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Based upon the scorer’s own unstructured assessment of the animal, a mark is made on a 100-m line, with the 0-mm end representing no pain and 100-mm end representing the worst possible pain
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Simple to use
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• Significant inter-individual variability
• Subjective
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Pain Relief Medication
Analgesia is a state of reduced sensitivity to pain. Analgesics interrupt the ascending pain pathway at various points and therefore suppress the sensation of pain.
Types of Analgesics
Various types of analgesics are commonly used in veterinary medicine. They include:
- NSAIDs: Nonsteroidal anti-inflammatory drugs
- Local: Local anaesthetic preparations
- Opioids: Narcotic analgesics
- Glucocorticoids: Steroidal anti-inflammatory drugs
NSAIDs
Examples include: meloxicam, carprofen (Rimadyl®), ketoprofen, phenylbutazone, aspirin, acetaminophen (paracetamol), robenacoxib (Onsior®), firocoxib (Previcox®), deracoxib (Deramaxx®)
NSAIDs act peripherally as a group inhibiting the production of the enzyme cyclooxygenase and reducing the level of prostaglandins in the tissue. These actions reduce the inflammation around the injured tissue and produce direct analgesia at the site of pain.
The cyclooxygenase is an enzyme that is responsible for formation of inflammatory mediators, particularly prostaglandins. It can be divided into 2 groups:
- COX 1, a ‘house-keeping’ enzyme
- COX 2, an enzyme responsible for inflammation and pain
Older NSAIDs tended to inhibit both COX-1 and COX-2. More recent drugs are being refined to only inhibit COX-2, as COX-1 is a ‘good’ enzyme.
The prostaglandin production that is inhibited is also not ‘specific’; therefore, some ‘good’ prostaglandins are also inhibited. This includes the prostaglandins that:
- Maintain gastrointestinal mucosal integrity
- Maintain normal platelet function
- Maintain normal renal perfusion
Due to this inhibition of prostaglandins, care must be taken when administering NSAIDs. They are contraindicated in certain situations, including:
- Geriatric patients
- Trauma patients
- Patients with active bleeding or bleeding disorders
- Renal failure patients
- Patients with liver disease
NSAIDs must never be administered together with corticosteroids.
Side effects of NSAIDs:
- Gastric irritation—This can manifest as vomiting, diarrhoea, gastric haemorrhage
- Renal compromise—Prostaglandins maintain and regulate the haemodynamic and blood flow of the kidneys
- Platelet dysfunction—Prostaglandins are also involved in the induction of aggregation (unification) of platelets; therefore, NSAIDs prolong bleeding times
Local Anaesthetics
Examples include: lignocaine, bupivacaine, Marcaine and prilocaine
Local anaesthetics produce reversible block of nerve impulse conduction peripherally and in the spine (epidural), depending on site of administration of drug. This produces a loss of sensation and function to the blocked area.
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Area
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Application
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Example
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Nerve/regional blocks
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Local anaesthetic is injected into or around the nerves of a specific area
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• Thoracotomy—intercostal nerve infiltration
• Dental surgery
• Distal limb surgery
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Epidural
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Local anaesthetic is injected into the area around the spinal cord
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• Stifle surgery
• Large animal caesarean
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Topical
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Applied directly on the skin/area of pain
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Opioids
Opioids prevent the message from being received in the brain. All opioids have slightly different properties, and the choice of drug used can be dependent upon several factors including:
- Patient presentation/disease/injury
- Type of pain
- Potency of drugs
- Side effects that may occur
- Length of duration
- Route of elimination
- Veterinarian preference
Opioids bind to specific opioid receptors in the central nervous system to produce analgesia. Due to each drug having different properties, some will stimulate and some will inhibit the various receptors. Therefore, combination of opioids must be used with great care, as one can disrupt the effects of the other.
Types of opioids
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Drug
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Use
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Duration
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Other
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Side effects
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Morphine
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Severe pain
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∼4 h
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• Action is dose dependent
• Higher doses or repeated doses will increase the analgesic effect
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• Vomiting
• Constipation
• Respiratory depression
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Methadone
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Severe pain
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∼4 h
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• Synthetic opioid
• Similar to morphine
• Quicker onset than morphine
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• Less side effects than morphine
• No vomiting
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Fentanyl
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Severe pain
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3–5 h
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• 100x potency of morphine
• Peak effect 5 min after IV
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Bradycardia
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Pethidine
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Mild pain
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1–2 h
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1/10th potency of morphine
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Can cause hypotension/histamine release if given fast IV
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Buprenorphine (e.g., Temgesic®)
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Mild–moderate pain
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8 h
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• Slow onset of action
• Overdose will cause no analgesia
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Slight cardiovascular effects
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Butorphanol (e.g., Torbugesic®)
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Mild, visceral or somatic pain
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∼2 h
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Potent antitussive
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Slight respiratory effects
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Summary
- Assess level of pain. Discuss your assessment with the attending veterinarian.
- Provide a clean and dry cage at all times. Patient should be away from draughts.
- Provide soft bedding to reduce pressure sores. Rotate animal if it is not able to move a particular body part at least 4 times a day.
- Provide cats with a nest, such as a cardboard box with padding for them to hide.
- Assess periodically if wound and sutures are intact.
- Assess if there is any unexpected bleeding or seepage from wounds or other sites.
- Check bowels and bladder at least twice per day.
- Ensure bandage is intact, dry and providing the protection and support required.
References
1. The Animal Industries Resource Centre course materials—Certificate IV in Veterinary Nursing