Measuring Pain Flashcards
What is the International Association for the Study of Pain 2019 definition of pain?
Pain = An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage
True or false
We need potential tissue damage to feel pain
False
We don’t need potential tissue damage to feel pain
When thinking about pain what do you need to be aware of?
It’s an individual experience
It has a protective function
What is the pathway that lets you feel pain?
First in the pain pathway is a pain inducing stimulus
The pain receptors then activate and translate and transmit signals through C and A-Delta fibres
The signal travels through the C and A-Delta fibres to the Peripheral Central Nervous Systems spinal cord
This triggers a reflex to move the body part away from the pain inducing stimulus
The pain signal will then continue up to the brains thalamus to feel the pain
What is Molony 1997’s definition of animal pain?
Animal pain = “ An aversive sensory and emotional experience representing an awareness by the animal of damage or threat to the integrity of its tissues
It changes the animals physiology and behaviours to reduce or avoid damage, to reduce the likelihood of recurrence and to promote recovery”
What are the 4 types of pain?
1) Nociceptive
2) Neuropathic
3) Acute pain
4) Chronic pain
What is nociceptive pain?
Nociceptive pain is acute sharp pain
Nociceptive pain responds to the following stimuli:
- Thermal
- Mechanical
- Chemical
You can get superficial somatic vs deep somatic vs visceral
What is neuropathic pain?
Neuropathic pain is where damaged and/or sensitised nerves fire in the absence of tissue damage
What is acute pain?
Acute pain has relatively short duration of pain
It has an obvious cause
It resolves with healing
It has a protective function
What is chronic pain?
Chronic pain could have multiple causes
Chronic pain persists after healing
It’s often refractory to treatment
What are the consequences of pain?
First there’s inflammation, tissue injury and nerve damage which leads to pain
The following systems will then activate:
- Neuroendocrine systems changes
- Sympathoadrenal activation
- Neuroplasticity (spinal cord and CNS)
- Inflammatory mediators “sensitising soup”
- Central processing changes
Activation of all these systems leads to infection and impaired wound healing
What is neuroplasticity?
Neuroplasticity is changes in the somatosensory system which will generate central sensitisation and facilitated CNS transmission
The firing of these neurones then causes hyperalgesia and allodynia
True or false
Pain can lead to more pain if severe or prolonged
True
Sensitisation can have a persistent effect, which causes what?
Hyperalgesia
Allodynia
Define hyperalgesia
Hyperalgesia = “An increased response to a stimulus which is normally painful”
Define allodynia
Allodynia = Pain due to a stimulus which does not normally provoke pain
What types of indicators can be used to assess pain?
Physiological indicators Behavioural indicators Pain scales/questionnaire Threshold test and cognitive bias Neurological indicators
Give examples of physiological indicators of pain
Tachycardia, hypertension and cardiac arrhythmia
Pale mucous membrane
Mydriasis
Sweating, trembling, hypersalivation
Increased urination or defication
Poor body or coat condition
Changes in stress hormones such as:
Cortisol
Glucose
Insulin
Adrenaline
EndorphinsWhat are the 3 disadvantages of physiological indicators of pain?
They're unreliable and non-specific if taken as a sole parameter
We need knowledge about physiology of the species evaluated to know what's normal
Errors are increased with
Disease
Fear
Stress
Handling
Anaesthesia
EtcTrue or false
Behavioural indicators generally vary between species
True
True or false
It’s hard to distinguish behaviour between species so we need to know the normal behaviour of each species in order to see if the animal is presenting pain behaviour
True
True or false
Behavioural indicators don’t vary within species
False
Behavioural indicators vary within species
True or false
Due to the behaviour indicator variations we need to rely on people who know the animal well to pick up the subtle changes
True
Give examples of behavioural indicators used to measure pain
Abnormal posture Abnormal activity Abnormal movement Abnormal gait Reluctance to move Depression, inappetence, dullness Manic behaviour Not grooming Trembling Poor interaction with people, hiding Non-interested in surroundings Decreased interactions with other animals Tooth grinding Poor cognition Ear-flicks Aggression Paying attention to the injured area or wound, hyperalgesia when palpated Vocalisation Whining, crying, howling Head hanging down, low tail carriage
What is the main disadvantage of behavioural indicators of pain?
Many of the behavioural indicators of pain can also indicate:
Poor general health
Medical problems
Anxiety or fear
Normal behaviour of the animal
How can you use pain scales/questionnaires?
This is where you assign scores to behaviours to quantify pain
What are pain scales/questionnaire created for?
They’re created for specific:
- pain conditions
- species
- environments
True or false
With pain scales/questionnaires it’s important to know if they’re validated or non-validated for specific pain types
True
What is a composite pain scales?
Composite pain scales combine different indicators together such as physiological and behavioural
What are pain scales/questionnaire used for?
They’re used to ensure that animals are frequently checked and levels of pain are assessed
If pain is present medication can be administered
When are pain scales/questionnaires usually done?
Pain scales/questionnaires are usually done alongside the animals physical examination and history
True or false
When using pain scales/questionnaires we also need to take into account variation
True
Give examples of pain scores
Simple descriptive scores
Numerical rating scale
Visual analogue scales
Explain what a numerical rating scale is?
Numerical rating scales are a total numerical score result from the sum of sub-categories each with various descriptors
They’re more thorough than simple descriptive scores and visual analogue scales
They’re also more time consuming
True or false
Facial expression scales of pain are also indicator of pain
True
What are the 5 disadvantages of pain scales/ questionnaires?
1) You need to still consider individual variability in the scorer and animal
2) There is no ‘gold standard’ pain scale
3) Some of them are very time consuming
4) The majority of them have been developed for peri-operative pain
5) There’s not many of them for:
- medical pain
- ear disease
- pneumonia
- chronic pain
- neuropathic pain
- other species
What are pain threshold tests also known as?
Threshold test = Quantitative Sensory Testing = QST
What happens in a threshold test/Quantitative Sensory Testing?
They use a repeatable stimulus to measure the response to pain
When the animal moves away from the stimulus that is it’s threshold
What can you use a threshold test/Quantitative Sensory Testing to detect?
Pain
Hyperalgesia
Allodynia
Test analgesic effects of drugs
What are threshold test/Quantitative Sensory Testing widely used for?
They’re widely used in preclinical studies evaluating pain and analgesic efficacy of drugs/therapies in rodents
True or false
Threshold tests are validated in different species
You need to know a baseline threshold for them all and what to expect when they’re feeling pain/hyperalgesia/allodynia
True
True or false
Threshold test/Quantitative Sensory Testing can be used to measure chronic and acute pain
True
What are the 4 disadvantages of measuring pain with threshold tests?
1) There are many confounding factors identified for each species
2) Training is needed to detect pain
3) Some tests need the animal to be restrained which may change the behaviour of the animal
4) They’re currently used in research situations not for clinical cases
True or false
Motor activity & gait analysis/weight bearing can be used as pain indicators
True
What are the 2 disadvantages of motor activity/gait analysis/weight bearing as an indicator of pain?
1) They have limited application in clinical practice
2) Some painful lesions of the foot may not result in lameness
Give examples of neurological indicators of pain
Electroencephalography EEG
FMRI
What are the disadvantages of using EEG’s to measure pain?
They’re invasive
The animal needs to be restrained
It’s not practical for non-research situations
It only evaluates activity of superficial cortex
What are the disadvantages of using an fMRI as a measure of pain?
fMRI are invasive
It’s an indirect marker of brain activity
The animal needs to be restrained and under general anaesthesia usually
It can be misinterpreted
It’s only used for pain assessment in the laboratory animals
What 7 things do we need to know when managing pain?
1) First we need to know what type of pain it is
This is because we need to treat it via the correct pain pathway/mechanism
2) We need to take into account whether the drug is short term or long term treatment
3) We need to be aware of side effects of the drugs
4) We need to think about the objective of the treatment
5) We need to be aware of the legal applications of using the drug
6) We need to be aware of the effects of the analgesic on the experiments lab animals
7) In chronic pain states you need to consider management of fear and anxiety to reduce pain perception
How do you pharmacologically manage pain?
You need to do pre-emptive analgesia
As much as possible we try to use multimodal analgesia
This means you get different drugs and combine them together to target different parts of the pain pathway
This allows you to use lower drug dosages which reduces side effects
What are the types of analgesics you can use and explain them?
Systemic
This means they’re taken either orally, interveneously, subcutaneously or intramuscularly
Local
This means you will administer the drug around the area of pain
Local analgesics carry less side effects
True or false
In many experiments the animal will be put under general anesthesia
General anaesthesia causes the animal to be unconscious with no nociception
False
General anaesthesia causes the animal to be unconscious but nociception is still present
This means analgesics are needed with general anaesthesia if you’re going to produce pain
True or false
With analgesics we will always try to choose the gold standard
True
True or false
For severe pain opioids are the gold standard
True
What 3 things must you consider when using pharmacological pain management?
You need to think about whether the animal can have the treatment at home or must it have the treatment in hospital
You must also consider side effects
You must also think about adjunctive therapies for chronic pain such as anxiolytics, antidepressants or antiepileptic drugs
What do local anaesthetics do?
Local anaesthetics inhibit completely the transmission of the action potentials in the synapses
Local anaesthetics prevent sensitisation and hyperalgesia/allodynia
True or false
Local anaesthetics are widely used for disbudding
True
True or false
In some cases general anaesthesia is required to apply local anaesthetics due to the animal moving too much
True
True or false
With non-pharmacological treatments you’ll try for a multimodal approach
True
Give examples of non-pharmacological pain management treatments
Acupuncture/electro acupuncture Corrective surgery Radiotherapy Physiotherapy Hydrotherapy Cryotherapy Environmental factors
