Analgesia Flashcards
What are the 5 major classes of analgesic drugs used in veterinary medicine?
-Opioids
- NSAIDs
- alpha 2 agonists
- NMDA receptor antagonists
- local anesthetics
T/F: your goal in veterinary medicine should be to eliminate all pain
True
Some argue that pain is an evolutionary protective mechanism and it is important from a learning standpoint, but it can delay healing and cause unpleasant downstream effects
Why is it so hard to localize the source of pain in animals?
They cant tell us where they are hurting
- pain is experienced in the brain and it often takes long pathways to get there- can be modulated along the way
What are some of the features of a perfect pain medication?
- can be administered in vairety of ways
- effective
- minimal adverse effects
-reversible
-cheap
-reaches site of pain
What are the pros and cons of opioids?
Pros:
- excellent analgesia
- relatively inexpensive
- many drug options
- minimal cardiovascular effects (good option in shock/heart failure cases)
- reversible
- sedation
Cons:
- possible respiratory depression (rare at analgesic doses)
- GI upset (vomiting, ileus)- often the biggest limiting factor
- histamine release
- mainly parenteral use
- sedation
- abuse potential
What is the oral bioavailability of codeine?
<5%
- not worth prescribing
Cats specifically can absorb buprenorphine across their gums
When are opioids best used in emergency?
-for acute severe pain (safe and effective)
- not as good for chronic pain management (beyond 24-48 hrs) due to adverse GI effects
What are the pros and cons of NSAIDs?
Pros: excellent analgesia, oral and parenteral formulations, several veterinary approved products, relatively inexpensive
Cons: possible GI ulceration, should not be used in patients with dehydration or hypovolemia (due to decreased RBF), not reversible
Describe the effects of NSAIDs on the kidney
-prostaglandins mediate renal autoregulation
- when prostaglandins are blocked by NAIDS, the kidneys are unable to adjust in the face of hypotension
How do NSAIDs cause GI upset?
In the gut prostaglandins help mediate the mucous and buffer production at the level of the gut lining
- when prostaglandins are blocked, the protective layer is affected which can make the stomach more predisposed to ulcers
Can dogs and cats take NSAIDs on an empty stomach?
Yes- as long as perfusion to the stomach is fine
When are NSAIDs best used?
Provide excellent analgesia for severe, chronic, and/or orthopedic pain
-use in only well hydrated patients
What are the pros and cons of alpha 2 agonists?
Pros: effective analgesia, powerful sedation, relatively inexpensive, reversible (atipamezole), good choice when sedation is also wanted
Cons: significant decrease in CO (limits use to stable patients), results in profound sedation and respiratory depression, can only be given parenterally (there is a new oral form however)
T/F: there is a linear correlation between dose of alpha 2s and the drop in CO
False- it is not linear
-it will always cause a decrease in CO regardless of the dose
-either patient is stable enough for an alpha 2 or they are not
What are the pros and cons of NMDA receptor antagonists aka ketamine
Pros:
-prevents wind up pain (an increase in pain intensity caused by the same stimulus over time)
-most effective if given before a painful stimulus (start giving intraoperatively, before first incision)
-reduces the amount of opioids needed for analgesia
-provides good sedation
-inexpensive
-both oral and parenteral options
-minimal to no GI effects
Cons:
-behavioral changes- hallucinogen
-inconsistent analgesia (best if part of multi-modal plan)
-best if used prior to painful stimulus
-muscle rigidity (rare at analgesic doses
-not reversible
