EXAM 3 Intro to Pain and Acute Pain Dr. Dahl Flashcards by o e

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

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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)

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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

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Explain Hyperalgesia and Allodynia

Hyperalgesia: exageratted pain

Allodynia: non-noxious stimuli causing pain (feather on the arm)

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What are the types of Pain?

-Nociceptive
-Neuropathic
-Inflammatory

Duration-wise:
-Acute
-Subacute
-Chronic

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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

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What is a common cause of neuropathic pain?

peripheral or CNS nerve injury

-chronically elevated blood glucose (diabetes)

-drug-induced

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What are drugs that are known to cause Neuropathic pain?

-cisplatin
-phenytoin
-amiodarone
-hydralazine
-metronidazole
-fluoroquinolones

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Characteristics of neuropathic pain

Often burning, stabbing, shooting, electrical

-> provoked by a stimulus that usually does not cause pa

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When is pain considered chronic?

-Longer than expected healing

-3 months

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Which type of Pain is chronic and acute (breakthrough)?

Cancer Pain

-Disease-related (tumor invasion, obstruction)
-Treatment (chemo, surgery, radiation)
-Diagnostic (biopsy)

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What are the Signs/Symptoms of Pain?

Signs:
-HTN
-Tachycardia

Symptoms:
-Diaphoresis (sweating)
-Mydriasis (dilation of the pupil)
-Pallor (pale skin)

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Tools to assess pain

-Unidimensional scales (quick, single item, focus on intensity)

-Multidimensional: questionnaire (more detailed)
McGill Pain Questionnaire
Wisconsin Brief Pain Inventory

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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

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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

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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

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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

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Characteristics of Acetinominophen

-Analgesic
-Antipyretic

NOT anti-inflammatory

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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

1. Total daily dose 2. convert to MME using conversion factor, may need to transfer to another formulation 3. account for cross-tolerance, renal and liver function, administration route and decrease by 25-50% 4. divide by the interval (q8h, q12h) 5. determine dose for breakthrough pain PRN -> 5-15% of the 24h dose (usually the IR of the same opioid)