Pain and Analgesia Flashcards
define chronic pain
lasting longer than 1 month,a ssociated with a p wide range of often subtle behaviourl disturbance
What are the 3 separate processes assocated with pain?
- nociception (sensory stimulus transmitted to the brain)
- perception (in CNS)
- behavioural reponse (varies according to species)
Define pain in animals
- aversive sensory and emotional experince
- awareness by the animal of demage or threat to the integrity of isssues
- changes the animals physiology and behaviour to reduce/avoid damage, v lieklihood of recurrence and promote recovery
What is hyperalgesia? Allodynia?
- increased sensitivity to nociceptive stimuli
- nociceptive sensatino of a NONPAINFUL stimulus
Clinical implicationd of hypersensitisation? What is this also known as? Which receptor is invovled and which drug can combat this?
- level of pain percieved is more severe
- anagesia less effective if given once pain present
- one type of analgesia may not be effectiveo nits own
= “wind up” d/t NMDA receptor involvement (ketmaine antagonist here)
Egs. of pain assessment
- NRS
- VAS
- SDS (no pain -> worst imaginable)
- Composite SS
- multidimensional scoring system
What is pre-emptive analgesia?
- administration of analgesics prior to onset of noxious stimuli (premed etc.)
Outline neural pathway of pain
- nociception
- mediated by substance P and glutamate
- synapse dorsal horn
- decussate
- travel in spinothalamic tract -> thalamus
[modulation within SC] - thalamocoritcal projections to the cortex
egs. of systeic analgesia
- opiods
- NSAIDs
- ketamine
- lidocaine
- a2 agonists
- tramadol (cheap, oral, lic)
- gabapentin/pregabalin
egs. local analgesia
- local anaesthetics
- opioids
- a2 agonists
define opium
- mixture of alkaloids from the poppy plant
define opioid
any natural occouring, semi-sythetic or synthetic compound that binds to opioid receptros and shares the properties of the natural ocourring endogenous opioids
Define opiate
- any naturally occourring opioid, derived rom opium eg. morphine, codeine
define narcotic
“to numb”
- was ued to deonte opioid, also describes non-opioid drugs of addictino
3 classifications of opioids?
> naturally occourring ocmpounds - morphine - codeine > semi-sythetic compounds - dimorphine (heroin) - dihydromorphone - buprenorphine - hydro-morphone > synthetic - pethidine - methadone - fentanyl, alfentanil, remifentanil - butorphanol, tramadol
What effects are mediated by each opioid receptors? LOOK UP and print table
delta: (DOP)
- spinal and supraspinal analgesia
- reduce gastric motility
kappa: KOP)
- spinal analgesia
- diuresis
- dysphoria
- species dependant (birds ^ no)
mu:
- analgesia, sedation, bradycardia , resp depression
- inhibition of GI transit, opioid tolerance…
n:
What is the only validated pain scale fro use in dogs?
Glasgow pain scale
What is an intervention score?
Pain scale sscore above which pain releif is administered
Which opioids are full m-agonists?
- morphine
- methadone
- pethidine (LIC)
- fentanyl/remifentanil
- etorphine (immobilon)
- papaveretum (omnopon)
Which drug is a partial m-agonist?
buprenorphine (LIC)
Which drug i a mixed agonist and antagonist?
- butorphanol (LIC)
Which pain scals have been validated in horses?
- composite orthopeadic pain cale
- PASPAS
Which drug are opioid antagonists?
- naloxone
- diprenorphine (revivon)
What is a partial agonist? eg?
- same overal actions of an agonist
- does NOT Produce maximal effect
- eg. buprenorphine
- partial m agonist
- analgesia, not as profound as full agonist
- (use milkd - mod pain)
What is a mixed ant/ag? eg?
- agonist at some recpetors
- antagonsit at others
- eg. butorphanol
- antagonist @mu, relatively poor analgesia
- agonist at K - some analgesia, sedation and dysphoria
Which levels can drugs work at? egs? LOOK UP
> transduction (nociceptors) - local analgesia - opioids - NSAIDs - steroids > transmission (peripheral nerves) - local anaesthetics > modulation (SC grey matter) - inhibit central sensitisation - local -opoids - a2s - NSAIDs - ketamine > projection (SC white matter) > perception (brain) - opioids - a2 ags
egs. routes of administration
> IV (NOT PETHIDINE)
- IM
- SC (variable absorption, not recommedned)
- oral (high 1st pass metabolism cf. humans, poorly absorbed)
- oral transmucosal (cats buprenorphine)
- spinal/epidural
- intra-articular
- transdermal (fentanyl patch or new LIC liquid fenanyl spoton)
Side effects of opioid analgesics
> arousal ^ or V
- CNS depression -> sedative effect (dogs, monkeys and people)
- CNS stimulation -> euphoria/dysphoria (exceitement and locomotor activity, cats, horses and ruminants)
- differences d/t interspecies differences in receptor distribution, presence of pain, dose and ROA, specific opoid
nausea and vomitiing
variation inupillary diamter
- cats mydriasis ( ^ catecholamine release, makes them light sensitive and aggressive)
- dogs miosis
thermoregulation
- v in dogs d/t thermal set point
- ^ cats, horses, swine and ruminants d/t muscular acitivty
resp depression
- m mediated effects (v responsivenesss to CO2)
- esp if coadministered with sedative
bradycadia
- vagal stim
- pethidine exeption
(eg. in GA, may need to give anti-cholinergic at the same time to avoid - or may be resp?? look up )
What act is involved in controlled drugs legislation?
1971 misuse of drugs act
> schedule 2 (pure agonists, controlled drugs)
- must be kept in locked cupboard
- records kpt of purchase and use
- special prescription requirements
- must be disposed of according to legislationi
> scedule 3 (partial agonist: bupreorphine)
- should be kept in locked cupboard with schedule 2, no record of use necesary
What is bupreorphine trade names?
vetergesic, bupracare
Which drug is currently exept from drug resitrcutions?
butorphanol
Indications and mode of action of ketamine? What schedule is it?
- schedule 4 currently ( no recording needed, going to be rescheduled -> schedule 2 d/t lots of abuse)
- adjuvant to pain managements
- sub-anaesthetic doses to prevent windup
- blocks NMDA R
> indications - skin grafts and burns orthopeadics and spinal surgery
- neurogenic pain (amputation)
Which analgesic canont be given IV?
KETAMINE
-> severe anaphylaxis
Tramadol - uses? What is it composed of? Mode of action?
- minimal evidence on effeciveness
- used because its cheap and not controlled
- can not be reversed by opioid antagonisits
> mixtuer of 2 stereoisomers with different effects and each metabolite will have different effects (complex drug ef. morphine etc.!) - 5HT and noradrenaline reuptake mediating == TCAs (amitryptaline etc.)
What are euphoria and dysphoria?
> euphoria
- kneading
dysphoria
- bad trip!
How can you treat dysphoria d/t opioids?
- partial agonist administration (buprenorphine)
Which opioid common causes vomiting?
Morphine
- methadone less commmon
What are schedule 1 drugs?
Vets cant use huan only
Actions of NSAIDs?
- anti-inflammatory (except paracetamol)
- analgesic
- anti-pyretic
- acute and chornic use
What are the 2 types of pain?
> adaptive (protecitve) - protective function - nociceptive pain - inflammatory pain > maladaptive (pathological) pain - serves no protective function - neuropathic pain (abnormal)
