Pain and analgesia Flashcards
Define pain
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
What is adaptive pain (protective)?
- protective pain
- nociceptive pain
- inflammatory pain
What is maladaptive (pathological) pain?
- serve no protective function
- neuropathic pain (abnormal)
Define acute pain
often has an obvious cause and is relatively short duration (hours to days)
Define chronic pain
pain lasting longer than 1 month, associated with a wide range of often subtle behavioural disturbances
Outline the 3 processes of pain
- NOCICEPTION: sensory process by which a noxious stimulus is transmitted to the brain (transduction, transmission, modulation)
- PERCEPTION of an unpleasant sensation in CNS
- BEHAVIOURAL response to pain -varies according to species
Define allodynia
painful response to a normally innocuous stimulus
Define hyperalgesia
increased response to painful stimulus
What does hypersensitisation mean?
- level of pain perceived is more severe
- analgesic drugs may be less effective if given once pain is present
- one type of analgesic may not be effective on its own
What causes variations in behaviour to pain?
- species (prey vs. predator)
- breed (labrador vs greyhound)
- demeanour
How can pain be assessed?
- scales: visual analogue or numerical rating
- simple descriptive: no pain to worst pain imaginable
- composite scoring system (based on different behaviours)
- multidimensional scoring system
What pain scoring systems are validated in horses? 4
- composite orthopaedic pain
- equine acute abdominal pain scale (EAAPS)
- complex numerical rating scale - postop colic
- post abdominal surgery pain assessment scale (PASPAS)
Ideal features of pain assessment in practice
- simple
- repeatable and reproducible
- minimal time
- allows effective pain management
Multimodal analgesic options
- opioids
- NSAIDs
- ketamine
- alpha-2-agonists
- local anaesthetics
What receptor does ketamine antagonise?
NMDA-R
Describe multi-modal analgesia
- attack pain pathway at multiple sites
- each method helps in overall control of individual pain
- more effective than using single method of analgesia
- allows lower doses of each drug to be used, reducing the risk of side effects
Use - gabapentin
usually for chronic pain
List systemic analgesia options
- opioids
- NSAIDs
- ketamine
- lidocaine
- alpha 2 agonists
- (tramdol)
- (gabapentin/ pregabalin)
- (chronic pain)
List local analgesia options
- local anaesthetics
- opioids
- alpha 2 agonists
Define opium
mixture of alkaloids from poppy plant
Define opioid
any naturally occurring, semi-synthetic or synthetic compound that binds to opioid receptors and shares the proerties of the natural occuring endogenous opioids
Define opiate
any naturally occuring opioid, derived from opium (e.g. morphine, codeine)
Define narcotic
from the Greek meaning ‘to numb’. It was used to denote an opioid but also to describe non-opioid drugs of addiction
Name 2 naturally occurring opioids
- morphine
- codeine
