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Flashcards in Pre-Meds II Deck (58)
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1
Q

Sedation/excitation occurs at what level?

A

Supraspinal - this is species/dose/breed dependent

2
Q

What are opioids derived from and how are they metabolized?

A

Derived from opium or synthetic; Hepatic metabolism (except remifentanil)

3
Q

Where are opioid receptors located and what are they?

A

CNS and peripheral NS; Mu, kappa, and delta

4
Q

What are the respiratory effects of opioids?

A
  • Respiratory depression - dose dependent
    • careful in patients with intra-cranial dz or resp dz
5
Q

Are opioids anti-tussive?

A
  • Yes; allows ET tube tolerance, but may incr risk of aspiration
  • Makes them useful for procedures like: tracheal stent, bronchoscopy, BAL
6
Q

What are the CV effects of opioids?

A
  • Bradycardia/AV blocks
    • incr parasympathetic tone
    • easily treatable w/ anticholinergics
    • otherwise - MINIMAL CV effects

*opioids can be safely used in patients with CV dz/instability!! - EXCEPT those w/ life threatening bradyarrhythmias/pacemakers

7
Q

What are the effects of opioids on pupillary diameter?

A

Miosis (mydriasis in cats)

8
Q

What are the GI effects of opioids?

A
  • Nausea/vomiting
    • both anti-emetics (emetic center) AND pro-emetics (CTZ)
    • the more lipophilic they are, the faster they reach the emetic center —> the LESS they vomit
      • ALL are lipophilic - hydromorphone and morphine are LEAST lipophilic = MOST likely to cause vomiting
9
Q

What are the effects of opioids on gastric motility?

A
  • They cause ileus
    • may initially cause incr large bowel movement (dogs + cats)
    • incr signs of colic - untreated pain also causes ileus!!
10
Q

What can be used to combat opioid-induced ileus?

A

Methylnaltrexone = opioid antagonist

  • does not cross BBB, reverse ileus w/o reversing CNS effects
11
Q

By acting on spinal, supraspinal, and peripheral receptors, opioids _________ pain transmission to the brain

A

Modulate

12
Q

What are common side effects observed with opioids?

A
  • dysphoria
  • resp depression
  • bradycardia
  • nausea/vomiting
  • aspiration pneumonia
  • ileus
  • urinary retention
  • hyper/hypothermia
  • hyperalgesia
13
Q

What are the effects of opioids on urinary system, immune system, histamine releases, and thermoregulation?

A
  • Urinary: urinary retention (can be reversed with naloxone)
  • Immune system: suppression vs. stimulation
  • Histamine release: morphine, meperidine +++, pruritis after neuraxial admin
  • Thermoreg:
    • hypothermia - change set point in hypothalamus (dogs pant but re not hot)
    • hyperthermia - cat, ferret, swine, horse, wild (capture)
14
Q

What are the main reasons to use opioids as premeds?

A
  • They are sedatives - esp if combined w/ alpha2 agonists/ace
  • contribute to intra-operative analgesia
  • MAC sparing effects
  • Minimal CV effects
  • Can contribute to smooth, pain-free recovery
15
Q

Which opioids are classified as full mu agonists?

A

Morphine, Hydromorphone, Oxymorphone, Methadone, Fentanyl, Remifentanil, Tramadol

16
Q

What is the general MOA of full mu agonists and why are they used as pre-meds?

A

They elicit maximal activation of mu receptors; used for moderate-severe pain, and often be used alone as a pre-med or in combo with ace or alpha2 agonists

17
Q

Describe the effects of morphine

A
  • lasts about 4 hrs
  • H release: slow IV admin
  • Nausea/vomit
  • Can be given many routes:
    • IV, IM, SQ, CRI
    • Neuraxial - long duration, urinary retention, pruritus
    • Intra-articular
    • On cornea
18
Q

What are the effects of hydromorphone?

A

Nausea/vomiting

More potent than morphine

19
Q

What are the effects of oxymorphone?

A

Less nausea/vomiting/H release

More potent than morphine

20
Q

What are the effects of Methadone?

A
  • Lasts about 4 hrs
  • Less nausea/vomit
  • No H release
  • Also NMDA antagonist
21
Q

Describe fentanyl and the different routes it can be given

A
  • IV (often give a bolus to patients w/ catheters in already)
  • Epidurally - less urinary retention, lasts < morphine
  • Not IM/SQ
  • Short duration = CRI
  • Trans-dermal patches: off label, lag time 12 h, duration 72 hr
22
Q

How is Remifentanil given, and for what types of patients is it often used? Duration?

A
  • IV only!
  • used in patients with severe liver disease
  • Lasts 3-5 min = CRI/IV only!
    • broken down via hydrolysis by plasmatic esterases

*rarely used as a pre-med

23
Q

Describe Tramadol, its MOA, and what is it’s active metabolite?

A
  • Synthetic weak mu agonist
  • MOA: NE and serotonin re-uptake inhibitor
  • Active metabolite: o-desmetyltramadol
    • more potent mu agonist - works better in cats
24
Q

What are ultra potent opioids used for and what are two examples?

A

used for capture; Etorphine and carfentanil

25
Q

Describe Etorphine

A
  • 4000 times more potent than morphine
  • antagonized with diprenorphine
26
Q

Describe Carfentanil

A
  • 10000 times more potent than morphine
  • Antagonized by naltrexone
27
Q

Describe Buprenorphine and some of its effects

A
  • a long-lasting partial agonist (6-8hrs)
  • binds tightly to mu receptor - hard to antagonize
  • causes minimal sedation/resp depression
  • no nausea/vomiting
  • good oral/trans mucosal absorption in cats

* only use for mildly painful procedures/peri-operative management!

28
Q

What is the FDA approved extended release formulation of buprenorphine?

A

Simbadol - one SQ dose = 24 hr analgesia

29
Q

What is an example of a agonist-antagonist opioid?

A

butorphanol

30
Q

Describe butorphanol

A
  • MOA: agonist at k receptors, antagonist at mu receptors
  • limited analgesic effect - often used in horses
  • good sedative/anti-tussive
  • does not cause emesis
  • 2 hr duration
31
Q

T or F: Butorphanol is a good choice as a pre-med if a patient needs surgery

A

False! Should only be used for non-painful procedures

32
Q

What are three opioid antagonists?

A

Naloxone, Naltrexone, Diprenorphine

33
Q

Descrbie naloxone

A
  • most commonly used opioid antagonist
  • works well on full mu agonists
  • will also revere analgesia!! (use low doses to maintain during recovery)
34
Q

Describe naltrexone

A

long acting opioid antagonist for Carfentanil

35
Q

Diprenorphine is an antagonist for what opioid?

A

Etorphine

36
Q

What two opioid can be used to reverse side effects of full mu agonists while retaining analgesia?

A

butorphanol and buprenorphine

37
Q

I have a dog presenting for acute onset of incoercible vomiting. I suspect a GI obstruction and need to sedate the dog for rads. If the obstruction is confirmed, I will then send the dog to surgery. What opioid should I use for sedation?

A. Butorphanol

B. Buprenorphine

C. Morphine

D. Methadone

A

D; morphine makes you vomit, butorphanol is a poor analgesic, buprenorphine is not a great analgesic either

38
Q

What is the main MOA of NSAIDs?

A

MOA: inhibit eicosanoid production by inhibiting COX

39
Q

T or F: COX-2 inhibition does not completely eliminate the side effects associated with classical NSAIDs

A

T - only measure of safety of COX2 selective NSAIDs over COX1 refers to their GI effects

40
Q

What are the GI side effects of NSAIDs?

A
  • GI injury - most common SE
  • due to prostaglandin inhibition–> direct mucosal irritation
  • Signs: V/D, inappetence, melena, hematochezia
  • Risk factors: concomitant admin of 2 diff NSAIDs or NSAID + corticosteriod; high doses
41
Q

What are the kidney side effects of NSAIDs?

A
  • kidney injury
  • role of prostaglandin - regulation of GF/RBF
  • Most likely - severe/persistent hypotension, low flow states
42
Q

What are the hepatic effects of NSAIDs?

A
  • hepatotoxicity
    • idiosyncratic, unpredictable
    • Intrinsic - predictable, dose-related
  • most commonly reported with carprofen
43
Q

What are the effects of NSAIDs on coagulation?

A
  • Inhibition of COX1 = decreased TXA = platelet dysfunction
    • aspirin - most selective COX1 inhibitor (plt take 9 days to reform)
  • COX2 inhibitors are actually pro-coagulants
    • AA metabolism produces TXA = incr plt fxn and vasoconstriction
44
Q

What are the contraindications of using NSAIDs for pre-meds?

A
  • Pre-existing:
    • GI dz, kidney dz, hepatic insufficiency
    • Decr effective circulating volume
    • Recent/concurrent steroid/other NSAID tx/nephrotoxic drug
    • MCT
    • Coagulopathies
    • Pediatric patients (Carprofen)
45
Q

What are some things to consider when giving NSAIDs perioperatively?

A
  • they treat pain/inflammation
  • when giving to patient already on NSAIDs as a pre-med–> higher risk of PONV and normal BP must be maintained
  • commonly given peri-operatively to horses
46
Q

My patient has OA and is receiving carprofen. I am about to anesthetize it for a TPLO. What considerations should I keep in mind for this dog during anesthesia?

A. Carprofen will contribute to perioperative analgesia

B. I need to monitor BP thoroughly and be proactive in treating hypotension

C. I will administer IVF to this patient

D. It may be beneficial to give this patient a gastroprotectant

E. All the above

A

E

47
Q

Which NSAIDs are approved for cats and dogs?

A
  • Carprofen (dogs > 6 wks)
  • meloxicam (chronic use in cats may cause AKF)
  • Rovenacoxib
48
Q

Which NSAID is for use in dogs only?

A

Deracoxib

49
Q

Which NSAIDs can be used in large animals?

A
  • Carprofen (horses and cattle in Europe/Asia)
  • Meloxicam
  • Firocoxib
  • Flunixin meglumine (only FDA approved NSAID for cattle)
  • Phenylbutazone (illegal in dairy cattle >20 mo; fine in horses)
50
Q

In healthy small animals, ___ sedation is used to facilitate IV catheter placement

A

IM

51
Q

Healthy (ASA I or II) Protocol in Dogs

A

you need something to sedate them IM so you can place an IVC

  1. Pick a sedative (alpha2 agonist) or tranq (ace)
  2. Add an opioid
  3. If aggressive consider adding hypnotic
52
Q

ASA > III (neonatal, geriatric) Protocol in Dogs and Cats

A
  • will likely be able to place an IVC w/o any sedation
  • pick a combo w/ minimal CV effects
  • opioid + benzos
53
Q

Healthy (ASA I or II) Protocol in a Cat

A
  • typically need higher dose of sedatives vs dogs to accept IVC
  1. pick a sedative (alpha2 agonist) - ace only in well behaved cats
  2. add an opioid
  3. if aggressive, consider adding hypnotic
54
Q

Practical tips for sedating horses

A
  • most tolerate IVC w/o no sedation
  • aggressive horses:
    • IV injection of alpha2 agonist +/- butorphanol
    • detomidine gel (PO)
    • tiletamine/zolazepam + alpha2 agonist for very aggressive (need padded box)
  • need to be very well sedated prior to indution of gen anesthesia
55
Q

What are signs of adequate sedation in horses?

A
  • head is below shoulder
  • not interestd in surroundings
  • ptosis
  • glazed eyes
  • don’t chew or pull tongue back in
56
Q

Tips for sedating small ruminants

A
  • typically tolerate jugular cath placements w/o sedation
  • a combo of opioid + benzo works well
  • alpha2 agonists may cause pulm edema
57
Q

Tips for sedating cattle

A
  • well tolerate IVC placement w/o sedation when restrained appropriately
  • calves will sedate w/ combo of opioid and a benzo
  • adult cows sedate w/ combo of xylazine and opioid (go down with xylazine)
58
Q

Tips for sedating swine

A
  • need to be heavily sedated to accept IVC
  • Hypnotics often useful for pre-med
    • ketamine
    • alfaxalone
  • Sedate with benzos
    • dexmedetomidine
    • ketamine
    • midazolam