Chapter 83: Pain Management

Pain is fundamentally understood as a subjective biopsychosocial experience rather than merely a sensory phenomenon, defined by the International Association for the Study of Pain as an aversive sensory and emotional experience. The chapter details the underlying mechanisms of pain perception through four interconnected processes: nociceptors detect harmful stimuli and initiate transduction, A-delta and C fibers transmit signals to the central nervous system, the brain modulates pain signals through neurotransmitter release including serotonin and endogenous opioids, and the cerebral cortex generates the final conscious perception. Pain classification distinguishes between nociceptive pain resulting from tissue injury, including somatic and visceral presentations, and neuropathic pain arising from nervous system dysfunction, which presents with burning or tingling sensations and resists traditional analgesics. Acute and chronic pain differ fundamentally in duration and psychological consequences, with chronic pain extending beyond three to six months and frequently accompanied by anxiety or depression. Assessment requires comprehensive patient evaluation including pain history, psychosocial screening for catastrophizing and distress intolerance, and standardized measurement tools such as numerical rating scales. Management follows a multimodal biopsychosocial approach integrating pharmacological and nonpharmacological strategies. Pharmacological options include non-opioid analgesics like acetaminophen and NSAIDs with their associated risks, neuropathic agents such as gabapentin and tricyclic antidepressants, opioids classified as natural, semisynthetic, or synthetic with unique considerations for medications like methadone, and emerging cannabinoid therapies. Nonpharmacological interventions encompass physical rehabilitation, yoga, transcutaneous electrical nerve stimulation, interventional procedures including joint injections, and behavioral health approaches such as cognitive behavioral therapy and mindfulness-based stress reduction. The chapter addresses the opioid epidemic, noting that primary care clinicians prescribe nearly half of all opioids and highlighting the need for prescription drug monitoring programs and medication-assisted treatments like buprenorphine. Critical attention is given to health disparities across racial and ethnic groups, sex and gender differences in pain reporting and diagnosis, age-related complications in geriatric populations, and pediatric-specific challenges. Finally, the chapter examines how the COVID-19 pandemic has exacerbated the opioid crisis and created new populations of chronic pain patients, particularly post-ICU survivors experiencing pain from immobilization and those experiencing neurological sequelae including neuropathy.