Pain management

Last updated: July 8, 2022

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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 nonopioids 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.


  • Pain (according to the International Association for the Study of Pain; 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 )
    • Unlike acute pain, chronic pain has no protective role in preventing further tissue damage and can be considered a disease entity in its own right.

Types of pain [2]

Physiology [3]

Sensitization [4][5]

  • Abnormal pain perception due to increased neuronal sensitivity to noxious stimuli (hyperalgesia) and/or reduced neuronal threshold to otherwise normal stimuli (allodynia) in response to local injury, inflammation, and/or repetitive stimulation.
  • Plays a major role in the generation and maintenance of chronic pain and neuropathic pain (e.g., postherpetic neuralgia)
  • Although not completely understood, the pathophysiology is thought to involve the following two mechanisms:
Overview of referred pain
Organ Dermatome Projection
Diaphragm C4 Shoulders
Heart T3–4 Left chest
Esophagus T4–5 Retrosternal
Stomach T6–9 Epigastrium
Liver, gallbladder T10–L1 Right upper quadrant
Small bowel T10–L1 Periumbilical
Colon T11–L1 Lower abdomen
Bladder T11–L1 Suprapubic
Kidneys, testicles T10–L1 Groin



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
    • Numeric rating scale (NRS): most common pain scale, evaluates pain on a scale from 0–10
    • Visual analog scale (VAS): visual equivalents suitable for children
    • Verbal descriptor scale
  • Pain diary: regular documentation of the pain intensity to identify peaks and triggers; enables treatment optimization

Pain can be difficult to assess in nonverbal patients; obtain supporting information from caretakers and use a specialized pain score, e.g., the nonverbal pain scale.

Be aware of implicit bias in the assessment of pain: Hispanic and Black patients are less likely to receive any and/or appropriate analgesia compared to White patients, even when reported pain scores are identical. [11][12]

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.


WHO analgesic ladder

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

  • 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-oriented): 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 ≥ 3×/day → inadequate analgesia likely; review the regular medication
  • Additionally, concurrent treatment with adjuvant drugs
Management of pain using WHO analgesic ladder [14]
Pain severity Nonopioid analgesics Mild opioids Strong opioids Adjuvant drugs
Step I Mild Include Avoid Avoid If required
Step II Moderate Include Consider Avoid If required
Step III Severe Include Consider Consider If required

Nonopioid analgesics are first-line agents for pain; prescribe them alone for mild to moderate pain and in combination with opioids for severe pain. [15]

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 [16]
NSAIDs [16]

Selective COX-2 inhibitor

  • Preferred second-line analgesic for mild to moderate pain [16]
  • Preferred over NSAIDs in patients with PUD
  • Use with caution in patients with renal or cardiovascular disease. [17]
  • See nonopioid analgesics for further information.

Combination analgesics

All patients being discharged with opioid medications should receive counseling on the use of prescription opioids.

Parenteral analgesics

Parenteral analgesics
Drug class Drug Important considerations

Analgesic suppositories

Topical analgesics

Topical analgesics
Drug Dose Indications

Adjuvant analgesics


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.

Avoid prescribing opioids, benzodiazepines, or muscle relaxants (alone or in combination) for treatment of acute nontraumatic low back pain. These agents do not improve pain outcomes and can increase the risk of harm. [25][26]


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. [27][28]

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

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


Acute pain [34]

Tailor pain management to the underlying condition.


Additional treatment considerations

Administer acute pain management promptly. Withholding acute pain management does not improve the accuracy of a physical examination.

In the emergency department, pain is frequently undertreated in children, patients with a different cultural or linguistic background from their provider, and patients with neurocognitive disorders, because of communication difficulties, atypical presentations, and implicit bias. [34]

Acute exacerbations of chronic pain

  • Management of acute-on-chronic pain requires significant empathy and skill.
  • The goal is a return to baseline function, not the complete alleviation of pain.
  • Follow local departmental policies if available.
  • Obtain a detailed pain assessment.
  • Assess for reversible causes of pain.
  • If no reversible cause of pain is determined:

Avoid routinely prescribing opioids for acute exacerbations of chronic pain. Local guidelines may, however, support the use of opioids in patients with advanced malignancy. Involve the patient's regular health provider in treatment decisions whenever possible.

Pain in sickle cell disease may represent a vasoocclusive event; manage new pain aggressively and perform a full diagnostic workup.

Assessment of pain in the ICU

  • Patients in ICU are typically unable to communicate and require a specialized pain scale [36]
  • Behavioral pain scale
  • Critical care pain observation tool (CCPOT)
    • Used to identify pain in critically ill patients.
    • Four items are evaluated and awarded points: facial expressions, body movements, ventilator compliance in intubated patients or vocalization in nonintubated patients, and muscle tension
    • ≥ 3 points indicates significant pain
  • For subjective grading of pain severity by the patient, see “Pain intensity scale
Pain intensity scales for critically ill patients
Behavioral pain scale score CCPOT score
Facial expression
  • 1 point for relaxed
  • 2 points for partially tightened
  • 3 points for fully tightened
  • 0 points for relaxed
  • 1 point for tense
  • 2 points for grimacing
  • Upper limbs
    • 1 point for no movement
    • 2 points for partially bent
    • 3 points for fully bent with finger flexion
    • 4 points for permanently retracted
  • Body
    • 0 points for no movement or normal
    • 1 point for protection
    • 2 points for restless or agitated
Muscle tension
  • N/A
  • 0 points for relaxed
  • 1 point for rigid or tense
  • 2 points for very rigid or tense
Mechanical ventilation compliance
  • 1 point for tolerating movement
  • 2 points for coughing, but tolerating most of the time
  • 3 points for fighting ventilator
  • 4 points for unable to control ventilation
  • Intubated patients
    • 0 points for tolerating normally
    • 1 point tolerating but coughing
    • 2 points for fighting the ventilator
Vocalization for extubated patients
  • N/A
  • 0 points normal tone or no sound
  • 1 point for moaning or sighing
  • 2 points for crying or sobbing

Pain management [37]

Be aware of the adverse effects of opioids (e.g., delirium, CNS depression, tolerance) or NSAID therapy!

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