Acute pain management

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Acute pain is typically sudden in onset and lasts less than one month. It indicates actual or potential tissue damage and is associated with trauma, surgery, and/or illness. Acute pain requires prompt treatment. Analgesics should be tailored to the underlying cause, patient factors (e.g., opioid naive or opioid tolerant, contraindications for NSAIDs), and care setting. The WHO analgesic ladder can help guide the selection of the most appropriate pain management strategy. When possible, nonpharmacological analgesia and nonopioid analgesics are preferred. Opioids should only be used if the benefits outweigh the risks and additional precautions are taken to minimize associated harms (e.g., risk mitigation for opioid prescribing). Patient-controlled analgesia (PCA), self-administered by the patient and delivered intravenously by an electronically controlled infusion pump, is used for severe acute pain that is difficult to manage and expected to be of short duration. Management of acute exacerbation of chronic pain can be challenging because complete pain relief is not usually possible; the primary aim is to restore patients to baseline function. Pain management in the emergency department often involves local anesthesia, regional anesthesia, and/or analgesics for procedural sedation. Specialized pain scales and scoring systems are used to assess pain in patients who cannot communicate verbally (e.g., critically ill patients, neonates, and infants).

See "Principles of pain management" for more information on evaluation of pain, analgesics and dosages, nonpharmacological analgesia, and pain management in children.

• Provide prompt analgesia for severe acute pain.
• Evaluation of pain
  • Obtain a thorough patient history.
  • Perform a comprehensive physical examination.
  • Assess pain severity with a pain intensity scale.
• Document recent analgesic use (e.g., type and dosage).
• Tailor the treatment strategy to the patient, ; the underlying condition, ; and the care setting.
  • Use the WHO analgesic ladder as a guiding principle.
  • Maximize nonpharmacological analgesia and nonopioid analgesia whenever possible. ^[2]
  • See “Choice of analgesic for acute pain” for cases in which opioids are required.

Administer acute pain management promptly; withholding it does not improve the accuracy of a physical examination. ^[3]

See also “Management of pain using WHO analgesic ladder.” For specific dosages, see “Oral analgesics,” “Parenteral analgesics,” and “Adjuvant analgesics.”

Risk mitigation ^[2]

• Only prescribe opioids if the benefits outweigh the risks.
• See “Risk mitigation for opioid prescribing.”

Prescribing principles ^[2]

• Use immediate-release opioids rather than extended-release or long-acting opioids.
• Start at the lowest effective dose.
• Prescribe PRN doses rather than scheduled doses.
• Limit prescription duration to the expected duration of severe pain.
• Reevaluate the risk-benefit ratio if dosage increases are required. ^[2]
• See “Oral analgesics” and “Parenteral analgesics” for dosages.
• For management of overdose, see “Opioid overdose.”

Definition ^[4]

Patient-controlled analgesia is a pain management method that allows patients to self-administer predetermined doses of analgesic medication (typically opioids) via an electronically controlled infusion pump.

Indications

• For severe acute pain that is difficult to manage and is expected to be of short duration, e.g.: ^[4][5][6]
  • Trauma-related pain
  • Vaso-occlusive crisis in sickle cell disease
  • Postoperative pain (e.g., if oral analgesia is insufficient or contraindicated)
  • Labor pain
• Occasionally used in chronic pain (e.g., cancer pain)

Components and settings ^[5][6][7]

• Route of administration: IV (most common), epidural, transdermal
• Initial loading dose (optional): improves early pain control (e.g., in the postoperative period)
• On-demand bolus: patient-triggered, predetermined dose
• Lockout time
  • Minimum time between boluses
  • Allows each bolus to reach peak effect, which reduces the risk of overdose
• Continuous background infusion: basal delivery independent of patient input

General principles ^[5][6][7]

• Opioid therapy is typically used.
  • Morphine: most common
  • Hydromorphone or fentanyl: for patients with abnormal kidney function or morphine intolerance
• Consider a background infusion in patients with known opioid tolerance.
• Monitoring
  • Assess pain level regularly (e.g., every 1–2 hours). ^[4]
  • Evaluate respiratory rate and level of sedation regularly.
• Inadequate pain relief
  • Patient is not sedated: Consider increasing the IV bolus dose.
  • Patient is sedated: Consider adding nonopioid analgesics or regional anesthesia.
• Discontinue when oral analgesia is sufficient for pain control.

There is no consensus on optimal regimens; follow local protocols when available.

Standard-dose regimens

Bolus dosages differ based on patient context (e.g., reason for pain control, history of opioid use).

Complications ^[5]

• Adverse effects of opioids (e.g., nausea, sedation)
• Masking of new pathologies (e.g., thromboembolism, myocardial infarction): may delay diagnosis, leading to worse outcomes

PCA may result in slightly higher opioid doses but does not increase adverse effects; respiratory complications are usually due to prescribing or administration errors. ^[5]

General principles ^[3]

Management of acute-on-chronic pain requires significant empathy and skill. Follow local departmental policies if available.

• Establish treatment goals.
  • The goal of treating the acute episode is to allow the patient to return to baseline function.
  • Complete alleviation of pain is typically not possible.
• Obtain detailed pain assessment and review existing care plans.
• Consult the clinical provider in charge of long-term pain management whenever possible.
• Identify and treat reversible causes of pain, e.g., a new:
  • Comorbid condition (e.g., renal colic in patients with chronic back pain)
  • Episode of a recurrent condition (e.g., vasoocclusive crisis in patients with sickle cell disease)
  • Condition that affects pain medication metabolization (e.g., malabsorption)
• Consider systemic barriers to accessing treatment.
• Consider admission for individual management of patients with progression of terminal illnesses if no reversible cause is identified.
• See “Chronic noncancer pain management” and “Pain management in palliative care” as needed.

Acute-on-chronic pain management in hospital-based settings ^[2][3]

• For patients already on an opioid regimen who have uncontrolled pain:
  • Preferentially add nonopioid analgesics (e.g., NSAIDs, acetaminophen, adjuvant analgesics).
  • If additional opioids are required:
    • Match duration to that of the expected superimposed severe pain.
    • Aim to return to baseline opioid dosage as soon as possible; consider a taper if additional round-the-clock opioids are required for more than a few days.
    • See also “Risk mitigation for opioid prescribing.”
• Individualized therapy is recommended for patients with sickle cell disease, cancer, and palliative care and/or end-of-life care needs. ^[2]

Involve the patient's regular health provider in treatment decisions whenever possible and be aware of the potential for drug diversion of prescriptions made by other health providers.

Severe pain

• Follow approach to acute pain for choice of analgesic. ^[3]
• For specific dosages, see "Oral analgesics," "Parenteral analgesics," and "Adjuvant analgesics."
• Reassess pain severity every hour, or more frequently if necessary.
• For emergency procedures, consider analgesics for procedural sedation.
• Consider a subanesthetic ketamine infusion as a stand-alone treatment or an adjunct to opioids. ^[8]
• See also "Acute-on-chronic pain management in hospital-based settings" and "Patient-controlled analgesia."

Extremity injuries

• Administer ice, elevation, and immobilization as indicated.
• Offer initial parenteral analgesics for pain caused by an acute deformity (e.g., fracture, dislocation) that is unresponsive to immobilization.
• Consider local anesthesia or regional anesthesia for localized pain.

Minimize undertreatment ^[3]

• ED patients' pain can be undertreated for a variety of reasons (e.g., communication barriers, atypical presentations, and implicit biases).
• Patients at risk of undertreatment include children, individuals of different cultural and/or linguistic backgrounds, and individuals with neurocognitive disorders.

Ambulatory opioid prescriptions

• Limit duration to < 3–5 days.
• Arrange rapid follow-up with a regular health provider for dosage adjustments.
• See also "Opioids for acute pain."

Pain in critically ill patients

Assessment of pain in the ICU

• Specialized pain scales: often used in ICU when patients are unable to communicate ^[9]
• Behavioral pain scale
  • Used to identify pain in critically ill patients on mechanical ventilation
  • Three items are evaluated and awarded points: facial expression, movement of the upper limbs, and mechanical ventilation compliance.
  • ≥ 5 points indicates significant pain
• 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
• Conscious patients: Obtain subjective grading of pain severity using a pain intensity scale.

Pain management ^[10]

• Pre-emptive analgesia for extubation and invasive procedures
• Multimodal analgesia depending on the severity and type of pain
  • Lowest effective dose IV opioids (first-line)
  • Adjuvant NSAIDs
  • Gabapentin or carbamazepine in case of neuropathic pain
• Consider using continuous infusions or regular doses of analgesics
• Regular assessment of the severity of pain and response to analgesia

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

Acute pain in children

See "Pain management in children."