A 38-year-old woman with a BMI of 32 kg/m² undergoes open abdominal hysterectomy under general anesthesia. Postoperatively, she is prescribed intravenous patient-controlled analgesia (IV-PCA) with morphine. The PCA settings are: demand dose 2 mg, lockout interval 10 minutes, 4-hour limit 30 mg, and background infusion 1 mg/hour. On postoperative day 2, the patient reports inadequate pain control despite pressing the demand button frequently. Nursing notes indicate she has been pressing the button 8–10 times per hour but receiving medication only once per 10-minute lockout period. Her respiratory rate is 16/min, SpO₂ is 96% on room air, and she is alert and oriented. Which modification to the PCA regimen is most appropriate?

Explanation

## Analysis of PCA Inadequacy and Titration Strategy **Current Problem:** The patient is experiencing inadequate analgesia despite frequent demand attempts. Her vital signs and respiratory parameters are reassuring (RR 16, SpO₂ 96%, alert), indicating she can tolerate dose escalation without safety concerns. **Why Option 0 is Correct:** - **Demand dose increase (2→3 mg):** Provides better pain relief per bolus without excessive cumulative exposure. - **Lockout reduction (10→5 minutes):** Allows more frequent dosing opportunities, matching her demand pattern (8–10 presses/hour). A 5-minute lockout permits up to 12 doses/hour if needed, accommodating her usage pattern. - **Rationale:** Both changes address the root cause—insufficient opioid delivery per unit time—while maintaining safety through respiratory stability and alertness. - **Guideline alignment:** ASRA and ASA recommend titrating demand dose and lockout interval based on patient demand frequency and pain control, not background infusion alone in opioid-naive patients. **Key Point:** In a patient with adequate respiratory reserve and inadequate analgesia, increasing demand dose and reducing lockout interval is the preferred first-line adjustment. Background infusion is typically reserved for patients with chronic pain or opioid tolerance. **Clinical Pearl:** Frequent button pressing without medication delivery ("button-pushing without effect") is a classic sign of inadequate lockout interval, not inadequate demand dose alone.