Anaesthesia: Clinical Induction and Maintenance and Pain Flashcards
What is pain?
An unpleasant sensory and emotional experience associated with, or resembling that associated with actual or potential tissue damage
What is nociception?
Relay of noxious stimulus from the periphery to the central nervous system
How does nociception translate to pain?
Integration and processing of nociceptive input by the brain allowing stimulus to be perceived as pain
What are the three types of acute pain?
Somatic
Visceral
Neuropathic
What is somatic pain?
Chemical, thermal or mechanical stimulus to skin, muscles, bones etc usually localised to injury site
‘sharp stabbing’ sensation
What is visceral pain?
Inflammation, ischemia (restriction of blood flow) or distension of viscera
Poorly localised, diffuse
‘Burning dull sensation’
Possible autonomic components- vomiting, sweating, tacyhcardia
What is neuropathic pain?
Primary lesion or dysfunction within the nervous system
May be localised or diffuse (depending on degree of nerve injury)
‘burning, tingling’ sensation may be intermittent
Can be component of chronic pain
What is the difference between acute pain and chronic pain?
Acute pain
Associated with tissue damage due to surgery, injury or disease. Rapidly alters animals behaviour (to minimise damage, optimise conditions for tissue healing), varies in severity, easy to treat
Chronic pain
Persists beyond expected time frame of tissue healing, may be associated with ongoing disease, maladaptive, often poorly responsibe to treatment
What are the three altered pain states?
Hyperalgesia
Allodynia
Spontaneous/idiopathic/functional pain
What is hyperalgesia?
Hyperalgesia is an altered pain state where exaggerated pain is felt in response to noxious stimulus
Use your brain- Hyper- algesia
What is allodynia?
An altered pain state where perception of pain sensation in response to normally non-noxious stimulus
Allo? that hurt!- unexpected
What is spontaneous/idiopathic/functional pain?
An altered pain state where pain arises in absence of detectable tissue or nerve injury
Difficuly to identify/prove in animals
Possible component of neuropathic pain- ‘phantom limb pain’
What are the two kinds of sensitisation?
Peripheral
Central
What is peripheral sensitisation?
Increased responsivness of nociceptors (reduced threshold)
‘Silent’ nociceptors activated
Occurs with tissue damage and inflammation
Altered expression of ion channels in nociceptive neurons
Causes primary hyperalgesia and allodynia at injury site
What is central sensitisation?
Increased efficiency of nociceptive signal transmission that may persist after end of nociceptive input
Changes in membrane exitability and upregulation of post-synaptic receptors (especially NMDA)
Results from intense, prolonged and/or repeated nociceptive input
Causes secondary hyperalgesia outside area of injury
May result in chronic pain
What happens if pain is not adequatley managed?
It causes unstable general anaesthesia
Poor animal welfare- 5 freedoms
Prolonged hospitalisation/delayed recovery
Development of central sensitisation- could lead to chronic pain- ongoing welfare problem for animal and owner/caregiver, behaviour issues
What are the 4 stages of nociception?
Transduction
Transmission
Modulation
Perception
What are the components of the ‘pain experience’?
Sensory- discriminative
Motivational- affective
Cognitive- evaluative
How can effective analgesia be provided?
Pre-emptive analgesia
Administration of analgesics prior to noxious stimuli maximises their effect, reduces sensitisation and enhances post operative analgesia
Once pain is established it should be treated aggresively- sensitisation to chronic/long term pain and difficult managment