Anethesia/Analgesia Flashcards
What are the characteristics of Silent/sleeping nociceptors?
present in both A- delta and C- fibers
high-threshold activated by tissue damage
important in peripheral sensitization
What is the most important tract in transmitting of nociceptive information?
spinothalmic tract
What cortical areas are activated during perception?
Reticular system: autonomic & motor response to do something
Somatosensory cortex: ids intensity, type & location & relates to past experience to memory
Limbic system: emotional/behavioral response to pain
What is the noradrenergic mechanisms?
happens in the locus coeruleus to the dorsal horn
stimulates adrenergic receptors
decrease in the release of substance P
How does the noradrenergic mechanism decrease the release of substance P?
Hyperpolarizing 2nd order neurons
depolarizing GABAergic neurons to inhibit pain transmission
What occurs in the Serotonergic pathway in the descending pathway?
Excitatory effects
release enkephalins which inhibit the release of substance P and hyperpolarizing 2nd order neurons
The inhibition of nociception is due to what?
The hyperpolarization of 2nd order neuron
What are the steps in the opioid system?
1) directly inhibit stimulus
2) Inhibit calcium influx prevents action potential which inhibits substance P
3) Promote potassium efflux membrane hyperpolarization which inhibits pain transmission
4) disinhibit descending modulatory pain pathways
Explain the mechanism behind primary hyperalgesia
Substance P will excite sensory and sympathetic fibers which allows for vasation of plasma proteins. this recruits inflammatory cells. A- delta and C- fiber activation activates silent nociceptors
Explain the mechanism behind secondary hyperalgesia (Wind-up).
NMDA receptor activation
influx of Ca
Increase sensitivity to glutamate
What is allodynia?
a phenomenon in which an area close to the site of tissue injury is painful if stimulated w/ a normal non-noxious stimulus
What are the effects of pain on the immune system?
Increased cortisol levels leads to impaired wound healing & decreased immune system
Increased ADH, catecholamines, renin, etc
Decreased in insulin
What are the effects of pain on the neuroendocrine system?
Hyperglycemia
impaired metabolism results in increase protein catabolism, lipolysis & cochexia
What are the effects of pain on the GI system?
Shunting of blood
Decrease motility
Decrease mucosal integrity
What are the effects of pain on the cardiovascular system?
Fluid retention
increased BP
decreased renal perfusion
Increased HR, SV, CO
What are the effects of pain on the respiratory system?
Ventilation perfusion mismatch
arterial hypoxemia
hypercarbia
What are the effects of pain on the coagulation system?
Increased platelet adhesiveness
decrease fibrinolysis
hypercoagulation
What is the cut off on the pan face scale for cats to get rescue analgesia?
> or = to 4/10
What is the difference between pain and dysphoria?
Dysphoria is difficult to distract/calm
opioids do not help
not identifiable source of pain
fixed dilated pupils unresponsive
What is acute (adaptive) pain?
an abrupt & brief event usually related to trauma, surgery or infection & medical diseases
What is chronic (maladaptive) pain?
Pain persists beyond a responsible time for the course of an acute disease or an injury to heal
What is somatic pain?
Originates from damage to somatic tissue (bones, joints, tissue)
sharp
localized
What is visceral pain?
arises from visceral injury
not well localized
associated with nausea & vomiting
What is neuropathic pain?
direct damage to peripheral nerves/spinal cord
described as burning/shooting pain
difficult to treat
What is adaptive inflammatory?
Spontaneous pain & hypersensitivity to pain in response to tissue damage & inflammation
occurs with tissue trauma
What is adaptive nociceptive?
Transient pain in response to a noxious stimulus
small aches and pains
protect the body from the environment
What is maladaptive neuropathic?
spontaneous pain & hypersensitivity to pain in association w/ damage to or a lesion of the nervous system
What is maladaptive functional?
hypersensitivity to pain resulting from abnormal processing of normal input
What are the characteristics of glutamate?
excitatory
multiple sites on this ionotropic receptor for drugs
antagonist used as a dissociative anesthetic
goes through astrocytes
What are the characteristics of GABA?
Inhibitory action: amino acid neurotransmitter
drugs include structrual analogs used for pain modification
Agonist
What are the characteristics of opioid receptors?
agonist used for analgesia
act on presynaptic sensory neuron to decrease pain causing neurotransmitter release
urinary excretion
metabotropic receptors
What are norepinephrine @ alpha 1 receptors?
Agonists
Stimulants
What are norepinephrine @ alpha 2 receptors?
Agonists
analgesics
tranquilizers
antihypertensives
emetics in cats
Is dopamine an agonist or antagonist?
Antagonist
What do opioids do presynapticly?
inhibit neurotransmitter release
What do opioids do postsynapticly?
decrease neuronal excitability through hyperpolarization of the cell membrane
What are pure opioid agonists? Give example?
activate the opioid receptors in the brain fully resulting in the full opioid effect
Methadone, morphine, hydromorphone, fentanyl
What are partial opioid agonists? Give example?
activate the opioid receptors in the brain but to a much lesser degree than full agonists
Buprenorphine
What are opioid agonist- antagonist? Give example?
causes stimulatory effect @ one receptor but block effects/causes less pronounced effect @ another
Butorphanol
What is an opioid antagonist? Give example?
binds to a receptor with high affinity & produces no effect. “Reversal”
Naloxone
What are the full mu agonists?
Morphine
Hydromorphone
Methadone
Fentanyl
What are the side effects of morphine?
histamine release
mania in cats
What are the side effects of hydromorphone?
panting in dogs
hyperthermia in cats
What are the side effects of methadone?
no histamine release
no vomiting
panting in dogs
What are the side effects of fentanyl?
no histamine release
no vomiting
bradycardia
chest rigidity
What are the partial mu agonist?
Buprenorphine
What are the side effects of Buprenorphine?
high affinity for receptor
plateau effect
not effectively reversed w/ antagonists
What opioid is a kappa agonist and a mu antagonist?
butorphanol
What are the side effects of Butorphanol?
high affinity for receptor
plateau effect
can reverse effects of pure mu agonists
Which opioid antagonist is the most potent?
Nalmefene/Naltrexone
Which opioid antagonist has the shortest duration?
Naloxone
Which opioid antagonist can control GI side effects without affecting the analgesia?
Methylnatrexone
What CNS effects do opioids cause?
Analgesia
Sedation
Excitation
Dysphoria & Euphoria
Thermoregulation
What respiratory effects do opioids cause?
depression of respiratory centers
decrease responsiveness to increased CO2
Dose dependent depression
anti-tussive effects
Panting
Cross placenta respiratory depression of neonates
What cardiovascular effects do opioids cause?
bradycardia
What effects does opioids have on horses & ruminants?
constipation, ileus
What route are opioids given that will cause nausea and vomiting?
IM
What are Mu effects on the urinary system?
increase ADH & natriuretic peptide, decreasing urine production
What opioid inhibits serotonin and norepinephrine reuptake?
Tramadol
Which species does tramadol work best in and why?
Cats because they have substantial M1 production via the P450 enzyme
What drugs are NMDA receptor antagonist?
