Nausea and Vomiting Management
Core concepts
Postoperative nausea and vomiting (PONV) is multifactorial. Identify risk factors (female sex, nonsmoker, history of PONV or motion sickness, postoperative opioids) and procedure factors. Use prophylaxis for patients at elevated risk, often with multimodal antiemetics from different classes.
Drug classes: 5-HT3 antagonists (ondansetron), corticosteroids (dexamethasone), dopamine antagonists (droperidol, metoclopramide), NK1 antagonists (aprepitant), antihistamines (dimenhydrinate), and anticholinergics (scopolamine). Know timing and side effects: QT prolongation with 5-HT3 antagonists and droperidol, sedation, extrapyramidal effects, and steroid effects in diabetic patients.
Nonpharmacologic measures: hydration, minimizing opioid and volatile anesthetic exposure, avoiding nitrous oxide in high-risk patients, and reducing gastric distension. Distinguish PONV from other causes of vomiting (bowel obstruction, ileus, pain, hypotension, hypoglycemia, opioid effect).
Traps
- Giving repeated doses of the same antiemetic class instead of switching classes.
- Ignoring QT prolongation risk when combining agents.
- Assuming vomiting is always PONV when it may signal a surgical complication.
- Forgetting that dexamethasone can raise glucose.
Rule of thumb
Match prophylaxis to risk and use different classes for rescue. If nausea persists despite treatment, reassess for pain, hypotension, ileus, or obstruction rather than stacking antiemetics.
Worked example
A high-risk patient receives ondansetron and dexamethasone intraoperatively but develops nausea in recovery. Rather than repeating ondansetron immediately, consider a different class (for example, a dopamine antagonist or NK1 agent) while checking blood pressure, pain, and hydration.