Premedication- Opioids And Muscle Relaxants Flashcards
What are the strongest available systemic analgesics?
Opioids!
- best choice for treatment of acute pain!
T/F: The benefits of using opioids during anesthesia is that you can decrease the dose of anesthetics and they cause minimal CV side effects
True
Which opioid is a mixed agonist-antagonist ?
Butorphanol
Antagonist on mu and agonist on kappa
Is butorphanol a good choice for strong pain?
NOPE
Can up-regulate pain because of antagonistic effect
Potency tells you the _______ and efficacy tells you the _________ of the effect
Dose; strength
Eg fentanyl is more potent than hydromorphone, therefore less dose is needed for the same effect
What drug is a partial mu agonist.
Buprenorphine
T/F: under appropriate conditions, a partial agonist may act as an antagonist of a full agonist
True
What effects do opioids have on CNS?
Analgesia!!
- great for acute pain, not so much for chronic
Decrease MAC
-species dependent (may increase the MAC in horses)
T/F: sedation by opioids is stronger if there is pain
True
What is the MOA of opioids to induce or inhibit vomiting?
Outside BBB- stimulate chemoreceptor trigger zone —> simulate vomiting
Inside BBB- inhibit vomiting center
Do lipid or water soluble opioids cause more vomiting?
Water soluble (eg morphine) - enter the brain slowly, therefore work more on CTZ peripherally to induce vomiting
What effects do opioids have on the CV system?
No direct effects!
-suitable for most risk patients
May indirectly decrease HR and BP be reducing sympathetic tone and increasing parasympathetic tone
What effects do opioids have on the respiratory system?
Depress
However healthy animals can tolerate high doses well
Opioids cause myosis in _______ and mydriasis in _______
Dog; cat
What are the effects of opioids on the GI ?
Dedication
Obstipation
Spasm of the sphincter of Oddi (hepato-pancreatic sphincter)
Normally opioids cause hypothermia, but post-op we are concerned about hyperthermia in what species?
Cats
When are opioids indicated?
Premedication!
-alone or combo with benzodiazepines/ ketamine/acepromazine/a2 agonists
Perioperative analgesia
Treatment of acute and chronic pain
What is the onset and duration of morphine?
Slow onset 30-40min
Long duration 4-6hrs
Morphine is metabolized in the liver to??
Active metabolite
Why may hydromorphone/oxymorphone be preferred to morphine in dogs?
Morphine may cause histamine release, especially after high doses
T/F: morphine is used for epidural analgesia
True
-duration 12-24hrs
What is the MOA of mathadone?
Full u agonist
NMDA antagonist
T/F: fentanyl has a long onset and duration of action
False
Onset 15-20min
Remifentanil has similar potency to fentanyl, but has what property that makes it more ideal for CRI?
Does not accumulate
Fentanyl accumulator after long infusions
What is a weak and short acting opioid analgesic that can worsen strong pain sensation, and may antagonize ful u agonists ?
Butorphanol
What opioid has a stronger effect than butorphanol but weaker than morphine?
Buprenorphine (partial u agonist)
Why do we prefer Buprenorphine in cats rather than full u agonists?
Cause less excitation
Can be given in oral mucosa
What is the onset and duration of action of Buprenorphine ?
Onset 20-40min
Duration 6-8hrs
How is tramadol administered?
PO
What is the MOA of tramadol
Inhibit NE and serotonin repudiate
-> metabolized in liver -> metabolite is a U opioid agonist
What are the opioid antagonists?
Naloxone
Naltrexone
What opioid antagonist is long acting and reveres long acting opioids like carfentanyl in wild animals
Naltrexone
What centrally acting muscle relaxant is used in large animal anesthesia?
Guaifenesin
Can guaifenesin be used as a sole agent for pre-medication ?
Nope
-no analgesia or unconsciousness
T/F: Guaifenesin is a muscle relaxant, therefore we should be concerned about significant impacts on cardiovascular and respiration
False
Has minimal effect on CV and respiratory system
What is the most common concentration used for guaifenesin?
5% GG in dextrose
What are complications if a >10% concentration of Guaifenesin is used?
Thrombophlebitis, hemolysis
What is the onset of effect of Guaifenesin?
Very short !!
Onset 2min
Duration 10-20min
What is the use of guaifenesin
Premedication
Part of triple drip - GG+ a2 agonsit + ketamine
