6. Pain and Analgesia Flashcards

Question

What is central hyperalgesia?

Answer 1

aka. 2nd hyperalgesia "wind-up pain" occurs w/ chronic pain Can reduce by providing pre-emptive analgesia Constant transmission of pain signals along spinal cord causes pain fibers to become hyper excitable Pain fibers more readily activated by stimuli originating anywhere in body. In other words, there is inc perception of pain originating from anywhere in body Harder to tx and persists longer

Answer 2

a type of hyperalgesia where pain is prod by a stimulus that would not normally cause pain ex. a feather stroking the skin Vs. hyperalgesia is an inc sense of pain to something that would typically cause lower levels of pain Responses are associated w/ neuropathic pain

Answer 3

using multiple drugs with each a diff mechanism of action. ex. each drugs target a different part of the pain pathway Advantages: 1. reduce dose of individual nalgesic drugs 2. when used peri-operatively, can reduce dose of anesthetic required 3. dec dose means fewer risks and s/e for each individual drug

Answer 4

1. pre-sx = pre-emptive analgesia as part of premed 2. intra-operative analgesia - main method of pain control is general anesthesia, GA stops conscious perception of pain, GA does not block steps 1-3 of the pain pathway, can add local anesthetic blocks 3. Post-operative analgesia I. immediately post-operative (in-hospital) ii. medication TGH, may be req for chronic use

Answer 5

admin b4 pain occurs ex. analgesic as part of premed Ideally, drugs used for pre-emptive analgesia should also provide or enhance sedation like opioids - excellent analgesia, A2 agonists - block nociceptors and substance P, ketamine - moderate somatic analgesia Pre-emptive analgesic that do not enhance sedation include NSAIDS and blocks w/ local anesthetics Avoid steroid use pre-op as may impair healing

Answer 6

1. Reduces overall req for anesthetic drug(s) - less CNS depression, fewer GA-related drug adverse effects, faster recovery 2. Reduces overall requirement for post-op analgesia - dec dose AND duration of post-op analgesia 3. Less pain = less stress; dec psychological costs associated w/ pain 4. most effective method of preventing windup

Answer 7

opioids - injectable opioids (morphine, hydromorphone, meperidine, butorphanol, buprenorphine, methadone), tramadol, fentanyl patch, gabapentin Monoclonal Ab therapy (solensia) Local anesthetics Ketamine A2 agonists Anti-inflammatories - NSAIDS, steroids

Answer 8

injectable: hydromorphone, fentanyl, oxymorphone, morphine, meperidine, butorphanol, buprenorphine, methadone TGH: butorphanol, buprenorphine, tramadol, fentanyl patch

Answer 9

drugs vary in potency, duration of action, s/e Pure mu agonists are best choice for analgesia Kappa-agonist can treat mild to mod pain Better analgesia if combined with NSAIDS major s/e = sedation, resp depression, GI stasis

Answer 10

comfortan Comes as 10mg/ml injectable in a 5ml vial For premed and for post-op pain w/ Ovariohysterectomy and castration in CATS - IM injection MOA: mu agonist opioid - binds and activates the mu opioid receptors

Answer 11

absorption: good absorption following IM injection - if accidental SQ injection, absorption is slower/unreliable Distribution: very large volume of distribution- drug likes to accumulate intracellularly in tissues Metabolism: primarily metabolized in the liver Excretion: via the kidneys - altho most of drug is metabolized in the liver prior to excretion, a sm amount is not metabolized and is excreted in its active form

Answer 12

potent analgesic via activation of mu receptors adverse effects are similar to all other mu agonists - resp depression, hyperactivity, occasional hyperthermia Contraindications - resp or cardiac failure, liver/renal dysfunction, known cases of hypersensitivity

Answer 13

* Pure mu-agonist (no kappa activity) * 50 – 100X morphine * REALLY short acting (20 min if given systemic) * Can give as an epidural * Can give as CRI for sustained analgesia * Can use at higher dose with benzodiazepines or alpha-2 agonists for induction and maintenance * Can also SEND HOME in the form of a sustained slow- release patch * Continuously releases small amounts of drug to maintain therapeutic levels * Side-effects same as for all mu-agonists

Answer 14

transdermal delivery system Perioperative analgesia for excellent pain control patches come in set sizes/doses

Answer 15

1. loc: thorax, inguinal, base of tail (D), neck (H) 2. prepare application site - close clip, 1cm clear margins (do NOT apply to skin that is broken), wipe skin w/ damp cloth (water only) 3. press firmly w/ hand for 2-3m 4. Coper patch with bandage 5. label cover (drug name, dose, time + date of application) 6. make sure anim cannot eat patch (cover well or e-collar) 7. remove when no longer effective - gloves optional, return to clinic to dispose; may be residual drug present

Answer 16

time to reach therapeutic lvls varies Dog: 12-24h Cat: 6-12h H: 12+h Duration (at therapeutic lvl) Dog: 3d Cat: 5d H: 2d

Answer 17

1. Never cut patch, cover half w/ water proof membrane 2. make sure anim cannot eat it 3. Make sure O do not have opioid sensitivities 4. Do NOT use if fever - do NOT place heat source next to patch (water bottle). will inc absorption and risk OD 5. Some patients develop skin reactions where patch is applied 6. Caution w/ children: bring back for taking off and disposal

Answer 18

mu-receptor agonist also inhibits reuptake of norepinephrine and erotonin moderate pain (half analgesia or morphine) PO only, need to wait fr animal to resume eating Onset: 4h to reach therapeutic lvls Compounded capsule or slow-release human tablet (breaking tab or disrupting coating takes away slow release) Works well in people, not so good in dogs Also emerging in cats, but more useful in dogs

Answer 19

Partial mu-agonist, indicated for: analgesia for mild to mod pain, take home opioid for cats Fewer mu-related s/e than hydro; little dysphoria: good in old/sick cats

Answer 20

versatile Can give IV, IM, SQ, epidural can give sublingual in cats - O squirts into buccal pouch or under tongue, drug absorbed thru oral mucosa, will NOT work if swallowed Longer duration of analgesia than most opioids (compared to tramadol(~8hrs)

Answer 21

neuropathic pain analgesic - anticonvulsant and for stress/anxiety in cats Mechanism largely unknown Helps tx chronic pain in D/C - prevent hyperalgesia Good take home as non-controlled lg range in suggested doses

Answer 22

sedation - start at low dose and increase gradually to fix Partially metabolized in liver renal excretion - caution w/ renal dz There is oral liquid form, contains xylitol so avoid generics available/compounded into capsules

Answer 23

very new chronic osteoarthritis therapy approved in CAD for use in cats Monoclonal antibody therapy - Ab's provided against nerve growth factor Given as injection for 1 mo pain control broken down the same way normal ab's (protein degradation) so minimal involvement of liver/or kidneys

Answer 24

drugs that "freeze" nerves, both sensory and motor neurons analgesia comes from inactivation of nociceptors indications - analgesia: significantly decreases GA requirements, local and regional nerve blocks Mechanism: inhibits Na channels in nerves > stops Na influx > neuron cannot depolarize/turn on and stops conduction of electrical impulse requires liver metabolism

Answer 25

topical (emla cream-contains lidocaine and prilocaine) Local blocks, epidurals, used alone for minor sx procedures used in combo w/ other analgesics, anes for pre-emp/periop/postoperative pain

Answer 26

nerve block to dx lameness in horses, dental extractions, dehorning, skin tumor removal, sprayed into larynx to aid in intubation (particularly in cats), regional blocks allows standing sx such as C-section, etc

Answer 27

all names end in "caine" lidocaine, mepivicaine, bupivicaine, cocaine, proparacaine

Answer 28

route of delivery and dose determines which nerve the drug acts on peripheral sensory nerves> analgesia Peripheral motor nerces > paresis/paralysis Spinal cord > dec transmission Autonomic nerves > affect autonomic nerve func Systemic delivery to cardiac cells > neg ionotrope - can be severe effects ranging from vasodilation to cardiac blockade

Answer 29

inc analgesia where needed At correct dose, few systemic effects Dec amount of GA required

Answer 30

tissue irritation, inflam temp to perma loss of nerve func if injected directly into nerve - intended to bathe nerve Allergy, anaphylaxis paresis, paralysis - if too lg a V of drug given in epidural, will diffuse up spinal chord > paresis, paralysis of diaphragm an dintercostal muscles > stop breathing Systemic overdose can cause fatal heart block or sympathetic block (blocks all sympathetic activity)

Answer 31

no reversals; tx is supportive care only All local anes have toxic dose - know when in practice Max safe dose set @ half toxic dose toxic dose in literature may vary and will depend on whether toxicity is considered to be neurotoxicity or cardiotoxicity or even death. It will depend on individual patient and person administering drug Depends on route and how fast

Answer 32

Part of toxic dose, close to 100% absorption

Answer 33

supportive care only - no reversals 1. check and recheck calculations 2. check the drug bottle 3. use proper syringe to measure

Answer 34

topical and injectable formulations 2 injectable formulations - lidocaine neat (only contains lidocaine (2%), can give local, regional or systemically, short-acting: 20m-1hr) Lidocaine (2%) w/ epinephrine - epinephrine causes vasoconstriction so drug stays in area longer, longer acting 1-2h, can only use locally; never give IV

Answer 35

carbocaine, injectable rapid onset (2-5m); duration of 90-120m Epidural in horses, NEVER give more than 10cc Excess volume will push drug cranially and paralyze diaphragm and intercostal muscles that can stop breathing can also cause heart block

Answer 36

marcaine, injectable or epidural NEVER give IV bc cardiotoxic 5-10m onset, 2~ duration Used for dental blocks and declaws

Answer 37

constant rate infusion diff from IV bolus (gives IV as single dose; may be slow IV), CRI (slow continuous admin of drug via IV, calculated as mcg/kg/min or g/kg/h) Req patient to be on IV fluids req micro-infusion pump - can administer a minute V of drug at a min or h rate used for analgesia and can also be used for injectable general anes

Answer 38

similar to CRI; slow continuous admin of drugs via IV Does not require a micro-infusion pump Drugs are added directly to IV bag - amount of drug added is based on patient's fluid rate, as patient receives fluid, will also receive drugs mixed in w/ fluids NEVER leave patient unobserved; there is a lot of drug in bag, if rate were to suddenly change patient could receive too much drug too fast and overdose CLEARLY label IV bags w/ name of all drugs added and how much added ALWAYS use a fluid infusion pump (more accurate)

Answer 39

drug is injected into epidural space blocks spinal nerves to a particular REGION Epidural drugs incl. opiouds, local anes and some A2 agonists loc along spinal cord depends on procedure and spp provides analgesia (excellent paincontrol, good duration) - hind limbs, pelvis and tail, abdomen, caudal thorax most epidurals have max V that cang ive

Answer 40

common for flan approaches inr uminants for c-sections, LDA sx

Answer 41

lower limb in cattle e.g claw amputation * anesthetic injected IV below tourniquet which keeps anesthetic at site to diffuse into SC tissue -blocks area below tourniquet

Answer 42

injection of opioids and/or local anes into joint space indications - elbow and/or stifle sx, equine lameness exams ex. morphine + bupivicane diluted in saline is instilled into a joint via a cath - immediately after joint closure provides 8-10hr post-op analgesia

Answer 43

Important: postop/trauma pain, chronic pain tx (arthritis, cancer) Consider: route of delivery, s/e, addictive potential, disposal and removal of fentanyl patches Most common: NSAIDs >> gabapentic > buprenorphine > butorphanol > fentanyl patches, codeine

Answer 44

used in conjunction w/ or as an adjunct to pharmacological therapy acupuncture, transcutaneous electric nerve stimulation (TENS) massage therapy, apply cold (acute injuries) or heat (chronic injuries) Physiotherapy chiropractic tx, laser or magnetic therapy chondroprotective agents nutraceuticals/Natural health products

Answer 45

relieving patient discomfort will help pain control Keep patient and cage clean or stall clean and dry comfortable bedding/quiet surroundings opportunity to urinate and defecate comfortable position - may have to turn every 2-3hr Reduce anxiety w/ toy or blanket from home Opthalmic ointment in unconscious patients to prevent corneal drying Comforting reassurance thru touch and talking, human contact

Answer 46

Opioids and NSAIDs

Answer 47

Local anesthetics

Answer 48

Steroids - analgesia is an added bonus when using steroid as anti-inflam and immunosuppresants

Answer 49

xylazine, dexmeditomidine Potentiates analgesia when used w/ opioid as pre-med or as neuroleptanalgesia Can give as a CRI Same s/e and contraindications as for sedation If given as epidural, will see less sedation than if given IM or IV - analgesia is longer lasting if given as epidural Reversing w/ atipamezole, tolazoline, yohimbine removes sedation and analgesia