Postoperative pain: multimodal analgesia

What it is

Acute postoperative pain is expected after almost every operation, and poor control has real costs: patients breathe and cough less, mobilise later, sleep badly, have more cardiac stress and thrombosis, stay longer, and are more likely to develop persistent pain after surgery. Pain starts when tissue injury activates nociceptors; the signal travels in peripheral nerves to the dorsal horn of the spinal cord and then to the brain, and inflammation sensitises both the peripheral nerves and the spinal cord. Multimodal analgesia uses drugs and techniques that act at different points of this pathway, so their effects add up while the dose of each, and especially of opioids, stays lower. The usual base is regular paracetamol and, when not contraindicated, a non-steroidal anti-inflammatory drug or a COX-2 selective inhibitor. Local anaesthetic techniques (wound infiltration, peripheral nerve blocks, epidural analgesia) block the signal before it reaches the spinal cord. Adjuncts such as ketamine, dexamethasone, intravenous lidocaine, alpha-2 agonists and gabapentinoids are added for selected patients. Opioids remain important for moderate to severe pain but are used as rescue or for the shortest time, with monitoring of sedation and breathing. The plan starts before surgery, is tailored to the patient and the operation (procedure-specific analgesia), and pain is measured regularly, including with movement and coughing.

Key points

• Pain is assessed with a simple scale (numerical, verbal or faces) at rest and on movement, together with function: can the patient breathe deeply, cough and walk?
• Patient-controlled analgesia lets the patient give small opioid boluses with a lockout, which keeps levels steadier; a background infusion increases risk.
• Epidural analgesia gives excellent dynamic pain relief after major abdominal or thoracic surgery but needs monitoring for hypotension, motor block and catheter problems.
• Gabapentinoids add sedation and dizziness, especially in older patients; their routine use is debated.
• The WHO analgesic ladder (non-opioid, then weak opioid, then strong opioid, with adjuvants) was designed for cancer pain; after surgery the order is often reversed, stepping down as pain improves.

Components

• Non-opioid analgesics: paracetamol, NSAIDs and COX-2 inhibitors, and metamizole where it is used.
• Local anaesthetic techniques: wound infiltration, fascial plane and peripheral nerve blocks, epidural and spinal analgesia.
• Opioids: oral for step-down, intravenous by nurse or patient-controlled, and neuraxial in small amounts.
• Adjuncts: ketamine, dexamethasone, intravenous lidocaine, alpha-2 agonists (clonidine, dexmedetomidine) and gabapentinoids.
• Non-drug measures: information before surgery, positioning, ice, splinting the wound for coughing, early mobilisation.

How it works

• Local anaesthetics block sodium channels in nerves, stopping the pain signal before it reaches the spinal cord.
• NSAIDs and COX-2 inhibitors reduce prostaglandin production at the site of injury and in the spinal cord, lowering sensitisation.
• Paracetamol acts mainly centrally; it has few side effects but its daily maximum must be respected, especially in liver disease or low body weight.
• Opioids act on mu receptors in the spinal cord and brain; side effects include sedation, respiratory depression, nausea, itching, constipation and urinary retention.
• Ketamine blocks NMDA receptors, reducing central sensitisation and opioid tolerance; it is useful in opioid-tolerant patients.

Step by step

1. Explain the plan before surgery and review usual analgesics and opioid use — expectations and tolerance change the plan.
2. Choose a procedure-specific plan with regular non-opioids and a regional or local technique when suitable — it reduces the need for opioids.
3. Add adjuncts for selected patients, such as ketamine for opioid-tolerant patients — each acts at a different step of the pain pathway.
4. Use opioids for breakthrough pain, titrated to effect — the lowest effective amount limits side effects.
5. Measure pain, sedation and breathing regularly, including on movement — function shows whether analgesia is adequate.
6. Step down to oral analgesia as pain eases, with a short opioid supply at discharge — long courses increase the risk of persistent use.

In practice

• Opioid-tolerant patients need their usual opioid continued plus a multimodal plan; early involvement of the acute pain team helps.
• Patients with obstructive sleep apnoea, older age, or kidney or liver disease are at higher risk of opioid side effects and need closer monitoring.
• Pain out of proportion to the operation, or new pain, may mean a complication (compartment syndrome, bleeding, anastomotic leak): examine before giving more analgesia.
• In orthopaedic surgery, peripheral nerve blocks and local infiltration analgesia allow early mobilisation; plan for the pain when the block wears off.
• Before discharge, prescribe a short, step-down course and explain how to stop opioids and store them safely.

Next step

• Call the acute pain team or the anaesthetist for pain not controlled by the plan, for opioid-tolerant patients and for epidural or catheter problems.
• If the patient is very sleepy or breathing slowly, stop opioids, support breathing, give an opioid antagonist if needed and call for help.
• Examine for a surgical complication when pain is unexpected, worsening or out of proportion.
• At discharge, give written advice on analgesics, opioid tapering, side effects and when to return.
• Follow up pain that persists beyond the expected healing time: it may be becoming chronic postsurgical pain.

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Elsewhere in DurgiPedia

• Pain and temperature: pathways and modulation
• Pain assessment and pain scales
• Pain assessment scales: numeric, visual analogue, faces, behavioural (FLACC) and in dementia
• Patient-controlled and epidural analgesia: the nursing checks
• Non-drug pain relief: what nurses do

Connections

← All of anaesthesia

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Postoperative Pain Control (StatPearls (NCBI Bookshelf), 2024); Multimodal Postoperative Pain Control After Orthopaedic Surgery (StatPearls (NCBI Bookshelf), 2026).

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