A 52-year-old man undergoes elective total knee replacement under general anesthesia. Intraoperatively, he receives 0.1 mg/kg morphine and 0.5 mg/kg ketorolac. In the post-anesthesia care unit (PACU), a patient-controlled analgesia (PCA) pump is set up with morphine: demand dose 2 mg, lockout interval 10 minutes, 4-hour limit 30 mg. At 2 hours post-op, the patient reports inadequate pain relief (VAS 7/10) and has pressed the button 12 times, receiving only 4 doses. His respiratory rate is 16/min, SpO₂ 96% on room air, and he is alert and oriented. What is the most appropriate next step?

Explanation

## Clinical Assessment The patient is experiencing inadequate analgesia despite appropriate PCA settings and stable respiratory parameters. The key findings are: - VAS 7/10 (inadequate pain control) - 12 button presses with only 4 successful doses (lockout interval preventing access) - Respiratory rate 16/min, SpO₂ 96%, alert and oriented (safe to escalate opioid) ## Management Approach **Key Point:** In PCA management, when a patient has inadequate pain relief with stable vital signs and normal mental status, the first step is to provide immediate analgesia with a clinician-administered bolus, then adjust pump parameters. **High-Yield:** The "lockout interval" exists to prevent overdose, but a patient pressing the button frequently without receiving doses indicates either: 1. Inadequate demand dose for the patient's pain/opioid tolerance 2. Lockout interval too long relative to drug onset time **Clinical Pearl:** A 5 mg IV morphine bolus (approximately 2.5× the demand dose) provides rapid relief while you assess the patient's opioid requirement. This is safer than immediately increasing pump parameters without reassessment. ## Rationale for Correct Answer The 5 mg bolus: - Provides immediate analgesia (morphine onset ~5–10 min IV) - Allows reassessment of pain and opioid responsiveness - Enables informed adjustment of demand dose (may increase to 2.5–3 mg) if pain remains inadequate - Maintains safety: respiratory parameters are stable, so escalation is justified ## Why Other Options Are Incorrect **Simultaneous increase of demand dose AND reduction of lockout interval:** While both changes may eventually be needed, making dual adjustments without an intervening bolus leaves the patient in pain for another 10+ minutes. The demand dose increase alone (to 3 mg) would not take effect until the next successful button press. **Ketorolac monotherapy:** NSAIDs are adjuncts, not replacements for opioids in moderate-to-severe post-operative pain. Ketorolac alone is insufficient for VAS 7/10 pain after major surgery. Additionally, the patient has already received 0.5 mg/kg ketorolac intraoperatively. **Intramuscular morphine:** IM administration is slower (onset 15–30 min), less predictable, and inferior to IV PCA for post-operative pain. It also removes patient control and increases nursing workload. IM is contraindicated in modern post-operative analgesia protocols.