EXAM 3 Intro to Pain and Acute Pain Dr. Dahl Flashcards
What is the pathway of Nociceptive Pain?
Transduction - Stimulation (of somatic or visceral tissue, could be thermal, chemical, mechanical -> is determination if this stimulus important enough?)
Conduction - Action potential (voltage-gated Ca+ channels)
Transmission - Transfer (passed on to the brain for processing)
Modulation - Fine-tuning (attenuate or inhibit it, could be endogenous (adrenalin) or exogenous (drug))
Perception - Experience
What are examples of chronic pain?
-Neuropathic (peripheral injury)
-Multiple Sclerosis, post-stroke pain (CNS pain)
-Fibromyalgia (chronic pain throughout the body)
-Irritable bowel (centralized where nerve injury or inflammation exists)
Neuroplasticity in chronic pain
-rewiring of pain circuits
-increase in dorsal horn neural discharge
->normal stimuli or minor injuries may be perceived as intensely painful
Explain Hyperalgesia and Allodynia
Hyperalgesia: exageratted pain
Allodynia: non-noxious stimuli causing pain (feather on the arm)
What are the types of Pain?
-Nociceptive
-Neuropathic
-Inflammatory
Duration-wise:
-Acute
-Subacute
-Chronic
Which organs are involved in Nociceptive pain?
sensory nerves detect tissue damage
-internal organs: (ill-defined, deep, aching, colicky (waves))
-somatic: musculoskeletal -> skin, muscles, bone, joints, ligaments
-> often localized, sharp, throbbing - constant and worse with movement
What is a common cause of neuropathic pain?
peripheral or CNS nerve injury
-chronically elevated blood glucose (diabetes)
-drug-induced
What are drugs that are known to cause Neuropathic pain?
-cisplatin
-phenytoin
-amiodarone
-hydralazine
-metronidazole
-fluoroquinolones
Characteristics of neuropathic pain
Often burning, stabbing, shooting, electrical
-> provoked by a stimulus that usually does not cause pa
When is pain considered chronic?
-Longer than expected healing
-3 months
Which type of Pain is chronic and acute (breakthrough)?
Cancer Pain
-Disease-related (tumor invasion, obstruction)
-Treatment (chemo, surgery, radiation)
-Diagnostic (biopsy)
What are the Signs/Symptoms of Pain?
Signs:
-HTN
-Tachycardia
Symptoms:
-Diaphoresis (sweating)
-Mydriasis (dilation of the pupil)
-Pallor (pale skin)
Tools to assess pain
-Unidimensional scales (quick, single item, focus on intensity)
-Multidimensional: questionnaire (more detailed)
McGill Pain Questionnaire
Wisconsin Brief Pain Inventory
What is the first-line treatment for pain?
Non-pharmalogic w/ or w/o analgesics
-Neurostimulation (acupuncture)
-Anesthesia (nerve block) ???
-Physical Therapy
-Surgical
-Psychological
-Cognitive Behavioral Therapy
-Massage
-Weight loss
-RICE – REST ICE COMPRESSION and ELEVATION
-Diets
Pharmacologic Approach with Opioids
- Non-opiod
+/- Adjuvant - Weak opioid
+/-Non-opioid
+/- Adjuvant - Strong opioid
+/-Non-opioid
+/- Adjuvant
starting too early with opiiods may lead to chronic opoiod use
What dose of opioids doesn’t require assessment of the appropriateness?
3-day supply up to 180 mg morphine equivalent
-don’t need to check the database (CSMD)
-don’t need to link the diagnosis and indiaction
What do prescriptions need for patients to be exempt from the law to be assessed for appropriateness of opioid use?
prescription must include the ICD-10 code
and the word exempt
-> for patients with diseases that require long-term opioid use
Characteristics of Acetinominophen
-Analgesic
-Antipyretic
NOT anti-inflammatory
What are the max doses of Acetaminophen?
OTC: <3000 mg/day
Rx: <4000 mg/day
Combo products: 325 mg
-> Box warning: hepatoxicity (< 4g/day)
in case of severe rash -> seek medical help
DDI Acetaminophen
can increase INR when used chronically
avoid alcohol use
Antidote in case of overdose: N-acetylcysteine
What is the primary use for Salcylates?
Cardioprotection
81-162 mg (baby dose aspirin)
(analgesic dose: 325-650 mg q4-6h)
What to be cautious about when using Aspirin in children?
Reyes syndrome (N/V, lethargy, confusion)
other side effects:
dyspepsia, heartburn, bleeding
fatigue, confusion, severe skin reaction
Which NSAID is thought to be safer for patients with CV diseases?
Naproxen
the evidence is not clear though
Which NSAID is commonly used for arthritis?
Diclofenac Rx
OTC: topical gel formulation: Voltaren gel
Which NSAID has a higher risk for GI toxicity?
Indomethacin Rx (also risk for CNS side effects)
Piroxicam (also risk for severe skin reaction)
-> need gut protection (PPI, misoprostol)
Which NSAID may be used for acute treatment?
Ketorolac (IV
has a 5-day total maximum treatment
-need a dose adjustment if:
>65y or
<50 kg or
high SCr
Which NSAID may be used in patients with reduced renal function?
Sulindac (not often seen)
-> also for patients on lithium (DDI drug)
lithium should not be apired with NSAIDs or ACEi
Which NSAID has the highest COX-2 selectivity?
Celecoxib
-often used for osteoarthritis and rheumatic arthritis
-BBW: sulfonamide warning
CAUTION with NSAIDs
-not appropriate to use 2 NSAIDs
-may use with baby aspirin -> outweigh benefit/risk
-increases bleeding risk (GI)
-avoid with cardiovascular issue
-can cause acute kidney injury (especially when used with ACEi, volume depletion)
When is a patient considered opioid tolerant?
-more than60 oral ME/day
-more than 25 mg transdermal fentanyl a week
-more than 30 mg oxycodone a week
-more than 8 mg of hydromorphone a week
anything else in opioid-naive
What is pseudo-addiction?
patients with drug-seeking behavior due to undertreated pain
Side effects of opioids
-Sedation
-respiratory depression
-constipation -> may need meds to improve bowel movement
-urinary retention
-N/V
-pruritus
-urticaria
-euphoria, dysphoria
Which opioids are likely to cross-react in opioid allergies?
opioids that have -cod -morph, norph in their name
nausea and itching are not true allergies
Which opioid may be avoided in renal-impaired patients?
Moprhine
it has metabolites M3G (50%) and M6G (15%)
they can accumulate in renal impairment
-> overdose
M3G: minimal analgesic activity and neuroexcitatory
M6G: analgesic activity and longer half-life than morphine
How potent is Hydromorphone in comparison to morphine?
Dilaudid
7-10x more potent
-> start low and go slow
start dose: 0.5 mg
-opioid naive
-elderly
-sleep apnea
-concurrent meds
What requirements do patients need to use fentanyl transdermal patches?
they must be opioid-tolerant
start with the lowest dose and titrate up
How should fentanyl be ordered for breakthrough pain?
q2h or q3h rather than q6h
bc it has a short duration
(onset is quick)
-> rapid IV administration can cause muscle rigidity
Which opioid has a warning for seizure risk and serotonin syndrome?
Tramadol (weaker opioid)
lower severity of GI side effects vs other opioids
Why has Meperidine fallen out of favor?
-it has poor PO absorption
-toxic metabolite: normeperidine
-> can cause seizure, especially in renal impairment (accumulation)
When are long-acting opioids not appropriate?
-in opioid-naive patients
-in acute pain (quick onset needed)
long-acting opioids:
-Oxycontin
-MS Contin
-Fentanyl transdermal patch
-Xtampza
Approach in pain management
mild: Acetaminophen, NSAIDs
moderate: consider opioids and adjuvants
severe: opioids (choose the right route) and adjuvants
->use around-the-clock dosing and breakthrough doses
-> monitor patient
How would a patient with an opioid disorder or chronic pain be treated?
may need a higher dose
-> they have increased pain signal (due to chronic pain)
-> lower threshold to set off pain signals
-> less response to substances that modulate pain
Multimodal analgesia opportuniites
NSAIDs
Tylenol
Gapapentin/pregabalin perioperatively
Which formulation is preferred for opioids?
PO before IV
Opioid conversion
- Total daily dose
- convert to MME using conversion factor, may need to transfer to another formulation
- account for cross-tolerance, renal and liver function, administration route and decrease by 25-50%
- divide by the interval (q8h, q12h)
- determine dose for breakthrough pain PRN
-> 5-15% of the 24h dose (usually the IR of the same opioid)
