Analgesia Flashcards
Pain is the _ vital sign
fourth
When pain elicits protective motor actions, what may the dog do?
try to bite after an IM injection
When pain elicits learned avoidance, what may it cause in the patient?
fear upon second visit to vet hospital
How may pain modify species behavior?
Different for individuals: seeking attention vs hiding
Untreated pain can affect
Behavior, Physiology, Metabolism, Immune system
What is nociception
detection by the nervous system for the potential for tissue injury
What does nociception protect the animal from?
painful or noxious stimuli
What is physiologic pain?
-Ouch pain
-Little or no tissue injury
-USEFUL: protects from injury
What is pathologic pain?
-follows tissue injury
-NO USEFUL FUNCTION: causes suffering
-Acute or chronic
Classifications of pathologic pain based on mechanism
Inflammatory, neuropathic, cancer, idiopathic
Classification of pathologic pain based on origin
Visceral (organs) or somatic (musculoskeletal- superficial vs deep )
Classifications of pathologic pain based on severity
none, mild, moderate, severe
What step of nociception is described?
Transformation of stimuli into sensory electrical signals (action potentials)
Step 1: transduction
What step of nociception is described?
Sensory impulses conducted to spinal cord
Step 2: transmission
What step of nociception is described?
Impulses are either amplified or suppressed
Step 3: modulation
What step of nociception is described?
Impulses are transmitted to the brain where they are processed and recognized
Step 4: perception
Drugs can be selected that will target specific receptors and block a specific step of nociception. _ _: targeting two or more of the receptors
Multimodal therapy
Why is multimodal therapy preferred?
reduces pain signaling by inhibition of multiple receptors and also allows lower drug dosages to be used, which decreases adverse effects and improves safety
What are the following consequences of?
-catabolism and muscle wasting
-immune system suppression
-inflammation and delayed wound healing
-anesthetic risk and increased anesthesia doses
-patient suffering
Untreated pain
Pathologic pain can result in
peripheral hypersensitivity or Primary Hyperalgesia
Primary hyperalgesia results from
tissue damage and constant stimulation of nerves (area close to the site of tissue injury becomes painful when stimulated with non-noxious stimuli)
What is secondary hyperalgesia
CNS hypersensitivity or windup
What drug can block secondary hyperalgesia
ketamine
What area is hypersensitive with secondary hyperalgesia
area further away from site of tissue injury (ex: you fracture your wrist and the forearm is touched)
What does secondary hyperalgesia result from
constant stimulation of spinal cord neurons (neurons become hyper excitable and sensitive)
Neuroendocrine changes: can results in a catabolic state and wasting, this looks like:
-ACTH release
-Elevated cortisol, norepi, and epi
-Decreased insulin
Sympathetic stimulation: can cause result in cardiac arrhythmias, this looks like:
-vasoconstriction
-increased myocardial work
-increased myocardial oxygen consumption
Pain elicits a _ response
stress (fight or flights)
The following describes _ _:
-Admin. of pain medications BEFORE pain occurs
-Commonly involves adding analgesic to premedication prior to anesthesia
-Reduces overall requirement for analgesia and duration of admin
-Prevents windup
Preemptive analgesia
What patients are less tolerant of pain
young
Behavioral responses to pain vary on the presence or absence of _
humans
Physical evidences of pain
-Changes in gait and level of activity
-Reluctant to lie down or constantly shifting position
-Vocalization
-Changes in facial expressions, appearance, and attitude
What is immediate postoperative vocalization called
Emergence delirium
What pain assessment tool is described?
-Absent, mild, moderate, severe
-SUBJECTIVE; no description so its up to the assessor to determine pain severity
Simple descriptive scales
What pain assessment tool is described?
-Advanced will use physiologic parameters, behavior and response to palpation to assign a #
-More objective
Numeric rating scales
What pain assessment tool is described?
-Uses a ruler- Left end= no pain , Right end= severe pain
Visual analogue scale
With effective analgesia, pain-associated behaviors will _
recede
Perioperative pain management includes:
preemptive analgesia and multimodal therapy
What stage is analgesia needed at of hospitalization or and tx
every stage
Choice of analgesic drug depends on
-severity and type of pain
-patients general condition
-route of delivery
GI effects of using opioids as analgesics
initial increased GI activity: nausea, vomiting, defecation followed by a slow down in GI activity: ileus, colic, constipation
Morphine is used for
moderate to severe visceral or somatic pain
What drug is described?
-Greater analgesic potency and sedative effect than morphine
-Fewer side effects and longer duration than morphine
-fewer tendencies to induce vomiting
-expensive schedule II drug
Oxymorphone
What drug is described?
-Opioid agonist
-Less potency but similar duration of effect compared with oxymorphone
-Will likely cause vomiting if not given IV
-Schedule II drug
hydromorphone
What drug is described?
-Synthetic opioid
-Characteristics similar to oxymorphone and hydromorphone
-Least likely to cause vomiting in cats and dogs
-Antagonist at the NMDA receptor
Methadone
What drug is described?
-One of the most potent analgesics
-Rapid onset and short duration of action when admin. IV
-Schedule II drug
fentanyl
What drug is described?
-Pure opioid agonist w/ less potent analgesic
-Admin. by SQ injection
-Wide margin of safety
-Used mostly as a preanesthetic in combo w/ atropine or ace
-When used w/ a tranquilizer, provides neuroleptanalgesia in puppies
-used w/ injectable NSAIDS
-Schedule II drug
Meperidine/ Pethidine
What drug is described?
-synthetic opioid agonist antagonist
-not as effective (for severe pain) an analgesic as a pure agonist
-produces less sedation, dysphoria, and respiratory depression
-can be used to reverse the effects of morphine and fentanyl
Butorphanol
What drug is described?
-A partial agonist
-post op analgesia in cats and dogs
-reverse effects of morphine and fentanyl
-delayed onset of action and longer duration
-used with sedative can prolong sleep times
-at high doses, resp. depression that is difficult to reverse w/ naloxone, may have to add doxapram
Buprenorphine
What drug is described?
-Agonist antagonist with greater antagonist properties than butorphanol
-weak analgesic and sedative
-used as reversal agent for opioid agonists
-fewer adverse effects
-not a controlled drug in the US
nalbuphine
Opioids as posted analgesics should be admin IM or SQ _ animal regains consciousness
before
Disadvantages of opioids as post analgesics
short duration of action, potential adverse reactions
Opioids used as IV infusion
morphine, fentanyl, oxymorphone, hydromorphone, methadone, butorphanol
How should IV infusion of opioids be administered?
initial loading dose given to effect followed by same dose given over 4 hours through constant flow
Opioids given as intraarticular injection are especially useful after _ or _ surgery
elbow or stifle
What is an opioid epidural injection
instillation of opioid into epidural space at lumbosacral junction
What are epidural opioid injections used to provide
analgesia to hind limbs, abdomen, caudal thorax, pelvis, tail
What drug is most commonly used for opioid epidural
morphine
When should an epidural be administered
after induction but before sx procedure
What should be done every 2-4 hours after epidural
reposition animal to prevent pulmonary atelectasis or prolonged pressure on superficial nerves
What do opioids admin. transdermally provide
convenient, long term opioid admin
What does a fentanyl patch provide?
analgesia for postop pain and pain associated with trauma, burns, cancer, and painful abdominal conditions
Signs of fentanyl patch overdose
ataxia and sedation (dogs); dysphoria and disorientation (cats)
What may increase absorption of fentanyl patch
heat
The following are _ :
-aspirin
-etodolac
-meloxicam
-ketoprofen
-firocoxib
-carprofen
-deracoxib
NSAIDS or nonsteriodal antiinflammatory analgesics (NSAAs)
How are NSAIDS eliminated
kidneys and GI tract
What are the most commonly used analgesics
opioids and NSAIDS
Local anesthetics as analgesics are used to prevent or tx
postop pain
Advantages of local anesthetics as analgesics
-complete anesthesia of affected area
-low toxicity
-rapid onset of action
Disadvantages of local anesthetics as analgesics
-short duration of action
-CNS and cardiac toxicity with repeated use
Alpha2 Agonists are used in _ to provide sedation ,muscle relaxation, and analgesia
horses
Corticosteroids as analgesics adverse effects
ulcerogenic
immunosuppression w/ long term use
hyperadrenocorticism
The following are examples of _ _:
-Acetaminophen and codeine (dogs)
-Fentanyl and meloxicam
-Morphine and injectable NSAID
-MLK
Multimodal therapy
Home analgesia
-Fentanyl patches
-NSAIDs
-Oral morphine
-Tylenol w/ codeine (dogs) and butorphanol
-Tramadol
The following are _ _:
-Acupuncture
-Transcutaneous electric nerve stim.
-Massage therapy
-Apply cold (acute) or heat (chronic)
-Physiotherapy
-Laser or magnetic therapy
-Homeopathic or herbal remedies
nonpharmacologic therapies
