Premedication (part 2) Flashcards
What are the three opioid receptors and where are they located?
u, k, d
- CNA & peripheral
Can opioids safely be used in patients with CV disease?
YES, it has minimal CV effect
- do not use in those with life- threatening bradyarrhythmias.
What opioids are most likely to cause vomit? and why?
Morphine and hydromorphone
- Least Lipophilic
Can pain cause ileus?
YES
Opiods work by…
acting on spinal, supraspinal & peripheral receptors to modulate pain transmission to brain (signal gets to brain- just confuses brain)
Opioids side effects
analgesia, sedation/excitation, respiratory depression, anti-tussive, bradycardia ( minimal CV effect), nausea/vomiting, urinary retension, hypothermia/ hyperthermia & histamine release.
What spp. feel hyperthermia with opioids?
cats & ferrets, also pigs, horses & wild
Why use opioids as a premed?
Sedation, provides peri-operative analgesia, spp. dependent MAC sparing effect, minimal CV effect & contribute to smooth pain-free recovery
What opioid is a full u agonist and NMDA receptor antagonist?
Methadone
When is full u agonist opioid used alone?
calm or sick dog
When is full u agonist opioid used with ace or a2 agonist?
excited or young animals
Which 2 opioid is rarely used as a premed?
Remifentanil- but iy is appropriate for patients with severe liver disease!
Tramadol
Since tramadol is a weak u agonist, why does it work in cats?
because produce an active metabolite (o-desmetyltramadol) which is more potent u agonist
When should a full u agonist be used?
moderate or severe pain
When should a partial agonist be used?
for mildly painful procedures; good post op!
Effects of buprenorphine
Long lasting ( 8 hr commitment), less effective analgesic, minimal sedation/ resp. depression with NO vomiting or nausea!
Examples of full u agonist?
Morphine, hydromorphone, oxymorphone, methadone, fentanyl, remifentanil, tramadol & ultrapotent opioids
Example of partial u agonist?
Buprenorphine
Butorphanol MOA
K receptor agonist and u receptor antagonist
When should you use butorphanol?
Non painful procedure (scope, imaging) BUT NOT a good choice if pt needs SX
Butorphanol effects
Limited analgesic effect (use in horse to limit ileus), good sedative, good anti-tussive and does not cause emesis
What is used to reverse the side effects of full u agonist?
Naloxone ( can reverse analgesia)
others- butorphanol and buprenorphone can reverse side effects while retaining analgesia!
NSAID effect
GI injury, kidney injury, ischemia, hepatotoxicity, coagulation
What does prostaglandin do?
increases blood flow to GI mucosa and increases mucus secretion/ bicarb!
It also regulates GFR & Renal blood flow
What should be done before starting a pt on NSAIDs?
PE, BWK + Urinalysis
If NSAIDs are given perioperatively, what should you monitor?
blood pressure!
Healthy (ASA I or II) Dog IM sedation
Sedative (a2 agonist) OR tranquilizer + opioid+/- hypnotic (aggressive)
ASA >III (neonatal or geriatric) Dog sedation (IV)
combo with minimal CV effect=
opioid + benzodiazepine
Healthy (ASA I or II) Cat IM sedation
Typically higher dose than dog
Sedative (a2 agonist, ace only works with well behaved cats!) + opioid+/- hyponotic (agressive)
ASA >III (neonatal or geriatric) cat sedation (IV)
combo with minimal CV effect=
opioid + benzodiazepine
Sedating an aggressive horse
A2 agonist +/- butorphanol (IV), detomidine (PO),
Telazol & a2 agonist (very aggressive)
T/F
Horses need to be very well sedated before induction of general anesthesia?
True, even if they are sick make sure you sedate!
How do you know a horse is adequately sedated?
o Lowered head ( below shoulder), uninterested in surrounding ( not responding to noise), ptosis/ glazed eyes, can pull tongue or don’t chew finger when placed in mouth!
Sedating Small ruminant
o Combination of opioid + benzodiazepine; a2 agonist can cause pulmonary edema (SO USE LOW DOSE!)
Sedating calf
combo of opioid + benzodiazepine
Sedating adult cow:
combo low dose xylazine + opioid
Sedating pig
Premed with hypnotic (ketamine or alfaxalone), Sedate with benzo (ex. pre med with dexmed+ ketamine+ midazolam) & include anti-emetic because they are prone to nausea/vomiting
