Postoperative Pain Management
Core concepts
Use multimodal analgesia: combine nonopioid agents (acetaminophen, NSAIDs when appropriate, regional blocks, ketamine, gabapentinoids in selected cases) to reduce opioid requirements and side effects. Understand opioid pharmacology, equianalgesic conversion, patient-controlled analgesia, and the risks of opioid-induced respiratory depression.
Regional anesthesia is central: neuraxial and peripheral blocks improve pain and reduce opioid use, but require monitoring for complications (local anesthetic toxicity, hematoma, infection, nerve injury). Recognize opioid adverse effects: sedation, respiratory depression, nausea, constipation, pruritus, and hyperalgesia with prolonged use.
Special populations: elderly (reduced clearance, fall risk), renal impairment (avoid morphine metabolites), obstructive sleep apnea (monitor closely), and chronic opioid users (tolerance, withdrawal risk, higher baseline requirements).
Traps
- Assuming more opioid is always the answer when pain is poorly controlled; look for the cause and add multimodal agents.
- Forgetting that NSAIDs are risky in renal disease, bleeding risk, or peptic ulcer history.
- Missing sedation as an early warning sign of respiratory depression before hypoxemia.
- Converting opioids without accounting for incomplete cross-tolerance.
Rule of thumb
Assess pain and sedation together. If the patient is excessively sedated with low respiratory rate, reduce opioids and support ventilation; escalate monitoring. Multimodal therapy lowers opioid dose and risk.
Worked example
A postoperative patient has a respiratory rate of 6 and is difficult to rouse after PCA morphine. Stop the opioid, support oxygenation and ventilation, monitor closely, and consider naloxone titrated to effect; also evaluate for other causes such as hypovolemia or residual anesthetics.