Pain

Pain

Evaluation
- General—a subjective experience involving physical, emotional, and cognitive dimensions
- Mechanism
  - Nociceptive pain—receptors triggered by tissue injury
    - Visceral pain (internal organ pain)
      - Pain in hollow organs is poorly localized, crampy, and/or colicky.
      - Pain in solid organs is poorly localized, achy, and/or dull.
    - Somatic pain—more easily localized, achy, dull, and/or throbbing
  - Neuropathic pain—due to pathologic effects on the central or peripheral nervous system
    - Described as a radiating electric sensation; can also be sharp and burning.
    - Associated with paresthesias, dysesthesias, hyperalgesia, or allodynia.
- Classification
  - Acute—typically follows an injury, but can be de novo; usually improves as tissue heals.
  - Chronic—pain lasting 3 to 6 months or pain which lasts ≥1 month longer than expected.
- Assessment
  - Scales
    - Numeric rating scale (1-10).
    - Visual analogue scale ( to ).
  - Frequent reevaluation is key
Management
- Pain management as outlined by the World Health Organization (WHO) Analgesic Ladder (Table 2.44.1)
Treatment—aim for the lowest possible effective dose to minimize side effects.
- Non-Nonsteroidal anti-inflammatory drugs (NSAID) analgesics
  - Acetaminophen (Tylenol) 325 to 650 mg PO q4h
    - Maximum dose is 1 g per dose; no more than 4 g per 24 hours.
    - For those with liver disease, decrease dose as there is a danger for liver toxicity.
- NSAIDS
  - Side effects
    - Gastrointestinal (GI) ulceration/bleeding
      - Therefore, consider coadministration with a proton pump inhibitor (PPI).
    - Potential nephrotoxicity in those with renal disease as well as in the elderly
  - Medications
    - Aspirin 325 to 650 mg PO/PR q4h
    - Ibuprofen (Motrin, Advil) 200 to 800 mg PO q6h
    - Naproxen (Naprosyn, Aleve) 250 to 500 mg PO q8h
    - Piroxicam (Feldene) 20 mg PO daily
    - Diclofenac (Voltaren, Cataflam) 50 mg PO q8h
- Cyclooxygenase-2 (COX-2) specific inhibitors
  - Celecoxib (Celebrex) 200 mg PO BID
    - May have less GI effects than NSAIDS, but be careful with increased cardiovascular risk.
- Weak opioids and opioid-like medications
  - Propoxyphene HCl (Darvon) 65 mg PO q4h = propoxyphene napsylate 100 mg PO q4h
    - Be careful with continued use as active metabolites accumulate over time.
  - Tramadol (Ultram) 50 to 100 mg PO q6h.
    - May trigger seizures; therefore, avoid in such patients.
- Strong opioids
  - Side effects
    - Slow GI motility, constipation (most common side effect)
    - Sedation and impaired psychomotor activity
    - Respiratory depression (the opioid-naive are more susceptible than non-naive)
    - Pruritus (itching)
    - Potential for addiction/abuse
  - Medications and single-dose equivalencies (Table 2.44.2)
    - Additional notes
      - Sustained release preparations:
        
        Morphine—MS Contin 15 to 30 mg PO q8h to q12h
        
        Kadian 20 mg PO q24h (or divided q12h)
        
        Oxycodone—OxyContin 10 to 160 mg PO q12h
      - Combination preparations:
        
        Percocet = oxycodone + acetaminophen
        
        Percodan = oxycodone + aspirin
        
        Lortab = hydrocodone + acetaminophen
        
        Vicodin = hydrocodone + acetaminophen
        
        Vicoprofen = hydrocodone + ibuprofen
        
        Tylenol no.3 = codeine 30 mg + acetaminophen 300 mg
      - Numerous routes of delivery for varying opioids
        
        IV (including patient controlled analgesia [PCA]), oral, rectal, subcutaneous, transdermal, intrathecal, epidural
        
        IM is generally avoided as it can cause pain itself.
        
        Fentanyl patch (Duragesic) 25 μg/hr—apply q72h.
        
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