Pain Assessment and Management
Framing pain
Pain is multidimensional - nociceptive, neuropathic, visceral, and 'total pain' encompassing psychological, social, and spiritual suffering. Begin by believing the patient's report, then characterize onset, quality, radiation, timing, and impact on function. Use validated tools: a numeric rating scale, a faces scale, or behavioral tools such as PAINAD or Abbey for advanced dementia. In cognitively impaired patients, guarding and grimacing matter more than a normal pulse or blood pressure.
Pharmacologic principles
Match drug to mechanism: acetaminophen and NSAIDs for somatic pain (watch renal, GI, and platelet effects, particularly in cirrhosis), opioids for moderate-to-severe nociceptive pain, and adjuvants - gabapentinoids, duloxetine, tricyclics - for neuropathic pain. Start low, titrate to effect, and prescribe a scheduled long-acting regimen with a breakthrough dose of roughly 10–15% of the total daily dose. Co-prescribe a bowel regimen; tolerance to opioid-induced constipation does not develop.
Rotation and safety
Equianalgesic tables are approximations. When rotating, reduce the calculated dose by 25–50% for incomplete cross-tolerance, then reassess within 24 hours. Avoid meperidine and codeine in renal impairment; morphine accumulates active metabolites (M6G) in renal failure, so fentanyl or hydromorphone is safer. Watch for opioid-induced neurotoxicity (myoclonus, hyperalgesia, delirium) and rotate or reduce the dose.
Worked example
A patient taking oral morphine 60 mg/day needs parenteral therapy. Oral to parenteral morphine is 3:1, giving 20 mg IV/day; reduce 25–50% for cross-tolerance, yielding about 10–15 mg IV/day as basal plus breakthrough dosing.
Trap: equianalgesic tables differ between sources, so questions test the principle rather than one memorized number.