How to Provide Analgesia Flashcards
what is peripheral sensitization
changes in the way we feel pain
how tissues detect and respond to stimulus
what is central sensitization
changes in the spinal cord
how does peripheral sensitization produce hypersensitization
what is “wind up”
responses to persistant or repeated barrages of nociceptive input
–> increase in firing rate in spinal cord neurones
increase in receptive area –> non painful stimuli –> pain (allodynia)
what does ongoing nociceptive discharge cause (4)
- decreased threshold for nociception
- increase perceived pain for given stimulus
- hyperalgesia
- non-painful stimuli become more painful (allodynia)
what is pre-emptive analgesia
the administration of analgesic agents before the onset of nociceptive stimulation
what is multimodal analgesia
use of more than one analgesic agent to provide analgesia
where are the areas analgesics can act (4)
- transduction
- transmission
- modulation
- perception
how do analgesics that act on transduction work and what is an example
ex. NSAID
affect the firing of nociceptors
how do analgesics that act on transmission work and what is an example
ex. local anesthetics
affect transmission of impulse to the spinal cord
how do analgesics that act on modulation work and what is an example
ex. opioids
affect spinal cord/brain
how do analgesics that act on perception work and what is an example
anesthesia blocks perception but not the impact of nociception
what are the clinical use of opioids (4)
- premedication
- intermittent bolus (IV/IM/transmucosal)
- infusion
- epidural
what are the opioids used for infusions
- morphine: cheap and effective 0.1-0.2 mg/kg/hr
- methadone: 0.08-016 mg/kg/hr
- fentanyl 2-10 mcg/kg/hr
what are the clinical uses of NSAIDs
- injectable/oral
- longer term use
where do NSAIDs act on the arachidonic acid pathway
where do steroids act on the arachidonic acid pathway
what are the clinical use of local anesthetics
- perineural blocks
- epidural
what are perineural blocks (2)
- limb: brachial plexus, RUMM, femoral, sciatic, digital
- dental: maxillary, mental, infraorbital, mandibular
what are epidural blocks
- lumbosacral: desensitize perineum, HL, (Abdomen)
- coccygeal (caudal): desensitize perineum, tail
what is intravenous regional anesthesia
common in cattle
with or without GA
tourniquet
usually lidocaine (not bupivacaine)
what are combined infusions
morphine, lidocaine, ketamine
what is the clinical use of alpha 2 agonists (for analgesia) (6)
- infusion: dexmedetomidine
- adjunct to local anesthetic in perineural block: prolongs effect
- epidural
- where pain is pre-existing
- situations predisposed to developing “chronic pain” (amputation)
- adjunctive analgesia with difficult to manage pain (bolus, infusion)
what are the routes of administration of analgesics
- oral
- SC/IM/IV
- transmucosal
- transdermal
- epidural
how is the oral absorption of opioids
variable
what are transmucosal analgesics
buprenorphine in cats
what are transdermal drugs
- fentanyl patches
- buprenorphine
- lidocaine
how do fentanyl patches work
aim for 2-4 mcg/kg/hr
effective plasma concentrations after 8-24 hours
lasts for 72 hours
what are the factors that affect transdermal drug uptake
- skin temp
- vasodilation
- dirt and/or cleaning
- subcut fat
what other drugs can be used for analgesia (5)
- maropitant: neurokinin 1 receptor antagonist
- grapiprant: EP4 prostaglandin receptor antagonist
- amitriptaline: tricyclic antidepressent
- amantadine: NDMA antagonism
- gabapentin
