A 35-year-old woman is recovering from an open abdominal hysterectomy. She is prescribed intravenous patient-controlled analgesia (PCA) with morphine. Which is the most common complication encountered in the immediate postoperative period with PCA use?

Explanation

## Most Common PCA Complication **Key Point:** Nausea and vomiting (PONV) is the most frequent adverse effect encountered with opioid-based PCA systems in the immediate postoperative period, occurring in 20–40% of patients receiving morphine PCA. ### Why Nausea and Vomiting Predominates Opioids trigger PONV through multiple mechanisms: 1. **Chemoreceptor trigger zone stimulation** — direct activation of the vomiting centre 2. **Vestibular sensitivity** — increased motion-induced nausea 3. **Gastric dysmotility** — delayed gastric emptying 4. **High morphine doses** — cumulative effect with repeated patient-triggered boluses ### Comparative Incidence of PCA Opioid Side Effects | Complication | Incidence | Timing | Severity | |---|---|---|---| | Nausea/vomiting | 20–40% | Immediate (0–6 hrs) | Mild–moderate | | Respiratory depression | 1–2% | Variable | Severe (requires intervention) | | Urinary retention | 5–15% | 6–24 hrs | Mild–moderate | | Pruritus | 5–10% | Delayed (hours) | Mild | **Clinical Pearl:** Although respiratory depression is more serious and requires close monitoring, it is far less common than PONV. PONV is the leading cause of patient dissatisfaction with PCA and often necessitates antiemetic prophylaxis or rescue therapy. **High-Yield:** Prophylactic antiemetics (ondansetron, dexamethasone, or metoclopramide) are routinely co-prescribed with opioid PCA to reduce PONV incidence and improve patient satisfaction. **Tip:** In exam questions, distinguish between *frequency* (nausea/vomiting) and *severity* (respiratory depression). The question asks for "most common," not "most serious."