A 52-year-old man with a history of chronic back pain (on long-term morphine 60 mg daily) is prescribed PCA morphine post-operatively. Regarding PCA programming in opioid-tolerant patients, all of the following are appropriate EXCEPT:

Explanation

## Identifying the Unsafe Practice **Key Point:** Omitting background infusion entirely in an opioid-tolerant patient is INAPPROPRIATE and potentially harmful. Tolerant patients require baseline opioid coverage to prevent withdrawal and maintain analgesia. ## Why Background Infusion Should NOT Be Omitted In opioid-tolerant patients: 1. **Withdrawal risk:** Abrupt cessation of chronic opioid therapy causes acute withdrawal (anxiety, tachycardia, diaphoresis, pain) 2. **Inadequate analgesia:** Bolus-only dosing cannot provide continuous baseline coverage 3. **Appropriate practice:** Background infusion should be set at 50–75% of the patient's chronic daily opioid requirement, then titrated based on response **Warning:** Completely omitting basal rate in a tolerant patient is a common exam trap—it appears "safer" but is actually dangerous. ## Correct Practices in Opioid-Tolerant PCA | Principle | Rationale | |-----------|----------| | **Higher bolus dose** | Tolerance requires 3–4 mg morphine (vs. 1–2 mg in naive patients) | | **Background infusion** | ESSENTIAL; prevents withdrawal and maintains baseline analgesia | | **Shortened lockout** | May be reduced to 8–10 min to accommodate higher demand in tolerant patients | | **Enhanced monitoring** | Pulse oximetry + capnography mandatory despite tolerance (respiratory depression still possible) | **High-Yield:** The mnemonic for opioid-tolerant PCA: **"HIGHER, INFUSE, MONITOR"** — higher bolus, background infusion required, enhanced monitoring essential. **Clinical Pearl:** Tolerance to respiratory depression develops more slowly than tolerance to analgesia; therefore, tolerant patients remain at significant risk of respiratory depression and require continuous monitoring.