• Clinical science
  • Clinician

Pain management

Summary

Pain is an unpleasant sensory and emotional experience that arises from actual or potential tissue damage. There are a number of ways to differentiate pain, the most common of which is the distinction between acute and chronic pain. Acute pain is a warning signal for actual or potential tissue damage and is associated with trauma, surgery, and illness. Chronic pain is generally defined as pain lasting beyond the normal tissue healing time. Standardized pain intensity scales are used to evaluate pain in a clinical setting. Pain management involves a multimodal approach with analgesic drugs, physical therapy, behavioral therapy, as well as interventional and surgical methods. The management of chronic pain follows the WHO analgesic ladder, a three-step algorithm and set of guiding principles based on using pharmacologic agents sequentially, escalating from non-opioids for mild pain to strong opioids for severe pain, in accordance with the degree of pain as reported by the patient. Each step of the ladder consists of regular medication and PRN medication as needed. If the analgesic effect is not sufficient at a certain level of the WHO ladder, advancing to the next step must be considered. Independent of the step, additional adjuvant drugs may be administered to potentiate analgesia and manage side effects of the analgesic drugs.

Types of pain

Definitions

  • Pain (according to the IASP ): “Pain is an unpleasant sensory and emotional experience arising from actual or potential tissue damage, or described in terms of such damage. [...] Pain is always subjective.” [1]
  • Acute pain: a warning signal indicating actual or potential tissue damage that triggers a protective reaction; typically associated with trauma, surgery, and acute illness
  • Chronic pain: pain that lasts beyond the normal tissue healing time; (6 months according to the IASP )

Types of pain

Dysfunctional perception of pain

Referred pain

Overview of referred pain
Organ Dermatome Projection
Diaphragm C4 Shoulders
Heart Th3–4 Left chest
Esophagus Th4–5 Retrosternal
Stomach Th6–9 Epigastrium
Liver, gallbladder Th10–L1 Right upper quadrant
Small bowel Th10–L1 Periumbilical
Colon Th11–L1 Lower abdomen
Bladder Th11–L1 Suprapubic
Kidneys, testicles Th10–L1 Groin

Referencs:[2][3][3][4]

Phantom limb syndrome

References:[5]

Evaluation of pain

To optimize pain management, a thorough history and assessment of pain is required prior to initiating treatment.

  • Pain characteristics (location, quality, temporal aspects, triggers)
  • Associated symptoms (changes in mobility and strength)
  • Pain impact (on daily life, sleep, activities)
  • Previous pain assessments and/or treatment
  • Pain intensity scale: subjective grading of pain severity by the patient
  • Pain diary: regular documentation of the pain intensity to identify peaks and triggers; enables treatment optimization

Pain is subjective! Pain scales are used to assess a patient's pain and response to pain management over time. They cannot be used to compare pain intensity between patients!

References:[6]

Treatment of pain

WHO analgesic ladder

The WHO analgesic ladder is a 3-step algorithm for the management of acute and chronic pain.

  • Principles
    • Regular analgesic (modified-release drugs, administered at fixed times and doses)
      • By the mouth: preferably, analgesics should be given orally.
      • By the clock: regular administration at fixed times, rather than on demand
      • By the ladder(symptom-orientated): if the patient is still in pain, it is necessary to go up a step
    • Appropriate PRN medication
      • Short-acting analgesics for peaks in pain
      • If PRN medication is required ≥ 3x/d → inadequate analgesia likely; review the regular medication
    • Additionally, concurrent treatment with adjuvant drugs
Pain severity Non-opioid analgesics Mild opioids Strong opioids Adjuvant drugs
Step I Mild pain - - If required
Step II Moderate pain - If required
Step III Severe pain - If required

Nonopioid analgesics are first-line agents for mild to moderate pain [7]
For both opioid and nonopioid analgesics, use the minimal effective dose for the shortest duration of time to minimize adverse effects. Pain intensity scales should be used in regular intervals to assess the success of pain management.

Oral analgesics

Oral analgesics
Drug class Drug Important considerations
Nonopioids Acetaminophen [8]
NSAIDs [8]

Selective COX-2 inhibitor

  • Preferred second-line analgesic for mild to moderate pain [8]
  • Preferred over NSAIDs in patients with PUD
  • Use with caution in patients with renal or cardiovascular disease. [9]
  • See nonopioid analgesics for further information.
Opioids

Combination analgesics

  • Consider combination analgesics for the management of moderate to moderately severe pain.
  • Follow the same precautions and contraindications for opioids and NSAIDs when prescribing these combination analgesics.

Parenteral analgesics

Parenteral analgesics
Drug class Drug Important considerations
NSAIDs
Opioids

Analgesic suppositories

Topical analgesics

Topical analgesics
Drug Dose Indications
Lidocaine
Diclofenac

Adjuvant analgesics

Anticonvulsants

Anticonvulsants are useful adjuncts in the management of neuropathic pain. They typically will not be helpful for acute pain, rather are more commonly used for chronic neuropathic pain.

Muscle relaxants

Consider muscle relaxants in patients with pain associated with muscle spasticity.

  • Cyclobenzaprine
  • Methocarbamol
  • Baclofen

Antidepressants

Tricyclic antidepressants and SNRIs can be helpful for chronic pain syndromes and neuropathic pain. Antidepressants for chronic or neuropathic pain are recommended by the American Society of Anesthesiologists in their 2010 guideline, but only duloxetine is FDA-approved for this indication. All others are off-label use. [19][20]

Intravenous patient-controlled analgesia

  • Infusion pump designed to release additional IV medication in response to patient's request
  • Indication: severe acute pain that is difficult to manage and is expected to be limited in duration

Management of side effects

Additional methods for pain management

There are a number of procedures available that complement the pharmacologic management of pain.

References:[22][23]

last updated 06/30/2020
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