Postoperative nausea and vomiting
Stem
A 34-year-old woman, 70 kg, is scheduled for laparoscopic sleeve gastrectomy. She does not smoke, vomited for a day after her last anesthetic, and gets carsick. She will receive opioids after surgery. She has type 2 diabetes on metformin and no cardiac history; her baseline ECG is normal.
Question
How will you assess and reduce her risk of postoperative nausea and vomiting?
Ideal answer
HeadlineApfel four of four, about 80%, and vomiting threatens her staple line: very high risk, so three or four antiemetics and a lower-risk anesthetic.
- Score her first with Apfel: female sex, non-smoker, history of PONV or motion sickness, expected postoperative opioids; each factor adds about 20%.1
- Dexamethasone 8 mg after induction, because its onset is slow, with glucose monitoring for her diabetes.
- Ondansetron 4 mg at the end of surgery, so its effect covers recovery.
- Aprepitant 40 mg orally before induction, or scopolamine patch, the patch the evening before, since she is young.
- Propofol TIVA instead of volatile and nitrous, plus opioid-sparing multimodal analgesia and adequate hydration, to cut her baseline risk.
Watch for: PACU vomiting: I first exclude hypotension, hypoxemia and pain, then rescue from a class not already given.1
Breaking down the answer
- Prophylaxis by number of factors — additive across classes; each drug cuts relative risk about 25%. The fourth consensus guidelines give at least two antiemetics to every adult with one or two risk factors, and three or four above two.1 Scoring before choosing shows organization.
- Dexamethasone timing and diabetes — slow onset, hence induction; 4–8 mg. In the PADDI trial a single 8 mg dose after induction reduced PONV, did not increase surgical-site infection (including in the 13% with diabetes), and caused slightly more hyperglycemia.2
- Ondansetron — the label says immediately before induction; I give it at the end. A second dose after failed prophylaxis adds no benefit.3 It prolongs the QT, so I avoid stacking QT-prolonging drugs in a patient with long QT.
- Droperidol and haloperidol — effective at low doses (0.625–1.25 mg droperidol); the boxed warning concerns QT prolongation and torsades, requires a 12-lead ECG before administration, and caps the initial dose at 2.5 mg.4
- Scopolamine patch — the label says remove it 24 hours after surgery.5 Dry mouth, blurred vision and confusion in the elderly; the Beers Criteria list it as highly anticholinergic, so I avoid it over 65.6
- Aprepitant — an NK1 antagonist with a long duration, given within 3 hours before induction;7 I add it for very high-risk patients and those for whom vomiting is dangerous: wired jaws, fresh fundoplication, or intracranial surgery.
- TIVA — removing volatiles reduces risk by about 25%, as much as one drug.
Follow-up question
Ninety minutes after surgery, despite dexamethasone, ondansetron, aprepitant and propofol TIVA, she is retching repeatedly in the PACU. What do you do?
Follow-up answer
HeadlineFailed prophylaxis: I examine her before treating the symptom, and tell the surgeon, because retching threatens the staple line.
Blood pressure, heart rate, pain, distension, blood in the vomit: hypotension, hypoxemia or uncontrolled pain can present as nausea. No repeat ondansetron within 6 hours, because a second dose of the same class adds little;3 a different class instead: promethazine 6.25 mg or haloperidol 1 mg. A small dose of propofol, 20 mg, is a PACU rescue in other patients, but she has had propofol throughout. Retching after a sleeve or fundoplication risks a staple-line leak or wrap disruption, so I rule out a surgical cause. I reassess her nausea, vital signs and abdomen within 30 minutes.
Pitfalls that cost points
- Forgetting the children's risk factors: surgery over 30 minutes, age over 3, strabismus surgery, and personal or family history.
- Prescribing the same antiemetic for rescue.
Rapid-fire
Q: Why does propofol reduce PONV? A: It has an intrinsic antiemetic effect and replacing volatiles removes the main anesthetic cause; the effect is greatest in the first 6 hours.
Q: Why is post-discharge nausea and vomiting separate? A: It occurs after the patient leaves; risk factors include female sex, history of PONV, age under 50, opioids in the PACU and nausea in the PACU.
Q: Why does scopolamine cause confusion in the elderly? A: It is a tertiary amine and crosses the blood-brain barrier, producing central anticholinergic syndrome.
Q: Why give dexamethasone carefully in tumor lysis risk? A: Steroids can precipitate tumor lysis in patients with lymphoma or leukemia.
Numbers to know
| Item | Value |
|---|---|
| Apfel risk: 0 / 1 / 2 / 3 / 4 factors | ~10 / 20 / 40 / 60 / 80%1 |
| Dexamethasone | 4–8 mg IV at induction |
| Ondansetron | 4 mg IV (label: before induction; commonly given at end of surgery)3 |
| Droperidol | 0.625–1.25 mg IV; label maximum initial dose 2.5 mg4 |
| Scopolamine patch | Delivers ~1 mg over 3 days; apply evening before, remove 24 h after surgery5 |
| Aprepitant | 40 mg PO within 3 h before induction7 |
Links
- Ambulatory anesthesia and discharge criteria, Volatile agents and nitrous oxide: when and when not, PCA and multimodal analgesia, Tonsillectomy and the bleeding tonsil, Morbid obesity and bariatric surgery
- Fourth Consensus Guidelines for the Management of Postoperative Nausea and Vomiting (2020)
Sources
- 1.Postoperative Nausea and Vomiting in Adults · OpenAnesthesia (IARS) · openanesthesia.orgSummarizes Gan TJ et al., Fourth Consensus Guidelines for PONV, Anesth Analg 2020;131:411-48.
- 2.Dexamethasone and Surgical-Site Infection (PADDI trial) · N Engl J Med (Corcoran et al.), 2021 · binasss.sa.crLibrary-hosted PDF of NEJM 2021;384:1731-41.
- 3.Ondansetron Injection: Dosage and Administration · Pfizer (FDA labeling) · pfizermedical.com
- 4.Droperidol Injection prescribing information · Drugs.com (FDA labeling) · drugs.com
- 5.Transderm Scop (scopolamine transdermal system) labeling · MedLibrary.org (FDA labeling) · medlibrary.org
- 6.2023 AGS Beers Criteria pocket card · American Geriatrics Society (via USC GWEP), 2023 · gwep.usc.edu
- 7.Aprepitant Capsules prescribing information · Drugs.com (FDA labeling) · drugs.com
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.