Analgesia Flashcards
What is the ISAP definition of pain?
An unpleasant secondary and emotional experience associated with or resembling that associated with actual or potential tissue damage.
What is the ISAP definition of nociceptive pain?
Pain that arises from actual or threatened damage to non-neural tissues and is due to the activation of nociceptors.
What is the ISAP definition of neuropathic pain?
Pain caused by a lesion or disease of the somatosensory nervous system.
Why is it important to know the difference between nociceptive and neuropathic pain?
- It can make a difference in how you approach pain management/treatment
- Neuropathic pain can be harder to treat
- Pain may be a consequence of a disease process – will it be neuropathic or nociceptive pain?
- For elective surgical procedures it is important to avoid damaging neural tissue
What is the ISAP definition of hyperalgesia?
Increases pain from a stimulus that normally provokes pain. Reflect increased pain on suprathreshold stimulation.
What is the ISAP definition of allodynia?
Pain due to a stimulus that does not normally provoke pain.
Distinguish allodynia and hyperalgesia?
For a pain evoked by stimuli that are usually not painful, the term allodynia is preferred. Hyperalgesia is preferred for cases with an increased response at a normal threshold or at an increased threshold.
What are the physiological signs of pain?
- Increased heart rate, blood pressure and body temperature
- Altered respiration rate and breathing pattern
- Stress hormones – cortisol, noradrenaline, adrenaline
- EEG activity – but can be pain or nociception
What are the similarities of behavioural signs of pain between cats and dogs?
- Hunched appearance
- Pain face
- Lack of grooming
- Inappetence
- Specific signs like lameness, depending on the condition
What are the differences between the behavioural signs of pain in cats and dogs?
Cats: absence of a normal behavioural repertoire, hide away at the back of cage, unwilling to relax, fear-aggression, resent human contact.
Dogs: positive behavioural signs rather than a reduced repertoire, more likely to seek attention, can be submissive or aggressive, may be more likely to vocalise
What are the behavioural signs of pain in rabbits?
- Immobility
- Profound depression
- Eyes half closed or shut
- Not grooming
- Avoiding attention
- Isolating themselves from other animals
- Bruxism
- Abnormal body position, such as hunched posture and abdominal pressing
- Change in temperament
What are the behavioural signs of pain in horses?
- Low head carriage
- Horse at back of stable
- Vocalisation – groaning and neighing
- Agitation
- Restlessness
- Weight shifting
- Tail swishing when no flies
- Lameness
- Limb lifting
- Abnormal distribution of weight
- Tucked up appearance
- Looking at painful body part
- Pain face
- Bruxism
- Sweating
- Muscle fasciculations
What are some additional indicators of pain in all species?
- Unkempt coat if grooming is difficult
- Loss of condition/weight loss due to appetite loss and/or loss of muscle tone if exercising less
- Slowing down and/or sleeping more
- Conversely could be more restless and fidgety
- May seen signs associated with reluctance to move
- Difficulty in accessing higher places
Describe the Glasgow composite pain scale for dogs.
Score is out of 20 if dog cannot stand and 24 if it can stand. Intervention level is 5/20 or 6/24
What is the drawback of the Glasgow composite pain scale for dogs?
Poor differentiation between pain and sedation, which is an issue in the immediate postoperative period
Describe the Glasgow composite pain scale for cats.
Maximum score is 20. Recommended intervention level is 5/20
What is preventative analgesia?
Administration of effective analgesia before, during and after the surgery/procedure, well into the postoperative recovery period
What are the aims of preventative analgesia?
Prevent upregulation of the nervous system in the face of noxious stimuli by administering effective analgesia. Reduction in both intensity and duration of the acute pain and a reduction in persistent/chronic pain.
What is multimodal analgesia?
Uses different classes of analgesic agents/techniques to attempt to block all the nociceptive/pain pathways.
What analgesic agents are used in veterinary practice?
Opioids
NSAIDs
Local anaesthetics
Alpha -2 agonists
Ketamine
How are opioids classified in terms of legal requirement?
- Most controlled drugs
- Full opioid agonists (methadone and fentanyl) are schedule 2. Special prescription, storage, destruction and record keeping requirements
- Partial opioid agonists (buprenorphine and butorphanol) are schedule 3. Special prescription and some have special storage requirements
Which receptor agonists produce analgesia?
µ agonists associated with analgesia. Full µ agonists provide the most effective analgesia
Name 3 full µ agonists and the species they are used in.
Fentanyl - dog, cat, horse, rabbit
Methadone - dog, cat
Pethidine - horse, less used now in dogs and cats
Name a partial µ agonists and the species it is used in.
Buprenorphine - dog, cat, rabbit