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Postoperative nausea and vomiting 

Postoperative nausea and vomiting
Postoperative nausea and vomiting

Keith G. Allman

, Iain H. Wilson

, and Aidan O’Donnell

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Subscriber: null; date: 17 September 2019

  • Carl Gwinnutt

    General principles [link]

General principles


  1. Nausea is the subjective sensation of the need to vomit.

  2. Vomiting is the forced expulsion of gastrointestinal contents through the mouth.


  1. ∼30% overall after general anaesthesia (GA).

  2. Up to 80% in high-risk patients.

Associated morbidity

  1. Decreased patient satisfaction, delayed hospital discharge, unexpected hospital admission.

  2. Wound dehiscence, bleeding, pulmonary aspiration, oesophageal rupture.

  3. Fluid and electrolyte disturbances.

Anatomy and physiology

  1. Activation of 5HT3 receptors in the gut results in stimulation of vagal afferents. Impulses conducted to the area postrema, in the floor of fourth ventricle.

  2. This area has a poorly developed blood–brain barrier, allowing detection of emetogenic substances in blood and CSF.

  3. Can be considered a ‘chemoreceptor trigger zone’ (CTZ).

  4. Afferents from CTZ, vestibular apparatus, vagus nerve, gut, and limbic system project to nucleus tractus solitarius.

  5. Multiple central structures throughout medulla are involved in vomiting, which is no longer considered a vomiting ‘centre’ but now designated a ‘central pattern generator for vomiting’.

  6. Efferents—cranial nerves V, VII, IX, X, and XII and spinal nerves to GI tract, diaphragm, and abdominal muscles.

  7. Receptor systems—dopaminergic (D2), muscarinic, serotoninergic (5-HT3), histaminergic (H1), and neurokinin (NK1).

Risk factors contributing to PONV

Key factors

  1. Females (3 × risk).

  2. Previous PONV or motion sickness (2–3 × risk).

  3. Non-smokers (2 × risk).

  4. Use of perioperative opioids.

  5. Estimated risk of PONV after inhalational technique is 10%, 20%, 40%, 60%, or 80% with none, one, two, three, or four of these factors respectively.

Other factors

  1. Surgery

    1. Breast, ophthalmic (strabismus repair), ENT, gynaecological, laparoscopic, laparotomy, craniotomy (posterior fossa), genitourinary, orthopaedic (shoulder procedures), thyroid.

  2. Anaesthetic

    1. Premedication—decreased risk after benzodiazepines and clonidine, increased risk after opioids.

    2. Type of anaesthesia—GA 11 × risk of regional technique, propofol TIVA less than volatile.

    3. Intraoperative drugs—opioids, nitrous oxide, inhalational drugs, IV drugs (thiopental, etomidate, and ketamine are emetogenic, propofol is possibly antiemetic), neostigmine (muscarinic effects on GI tract).

    4. Dehydration increases risk. Avoid too early resumption of food/fluids.

Management of PONV

PONV is multifactorial (multiple pathways and neurotransmitters); therefore a multimodal approach is most effective. Each drug results in similar relative risk reduction, giving an additive but declining absolute effect.

Pharmacologic methods

  1. Prophylaxis vs treatment remains controversial.

  2. Prophylaxis with ondansetron is reported to be cost-effective in high-risk patients where PONV >30–33%.

  3. Combination therapy—two or more drugs with different modes of action is more effective, e.g. ondansetron plus dexamethasone or droperidol.

Non-pharmacologic methods

  1. Acupuncture—pericardium (P6) point on palmar aspect of wrist. As effective as standard antiemetics but no side effects (NNT = 5).

  2. Others include ginger root extract, hypnosis, suggestion, and homeopathy.

Current research

  1. Neurokinin (NK1) receptors are found in the medulla and play a role in the nausea and vomiting pathway. Current research shows NK1 antagonists (e.g. Aprepitant) given prophylactically are more effective than ondansetron at reducing vomiting and have a similar effect at reducing nausea.

  2. Long-acting 5HT3 antagonists, e.g. palonosetron.

  3. Gabapentin reduces PONV as well as postoperative pain.

  4. Pharmacogenetics. Genetic polymorphism plays a role in transport, metabolism, and receptor binding of 5HT3 antagonists. This influences individuals’ response to drugs.

The vomiting patient

  1. Reassurance.

  2. Correct vital signs appropriately.

  3. Ensure adequate analgesia and hydration.

  4. Look for surgical cause (e.g. distended abdomen—insert or aspirate NG tube).

  5. Antiemetics:

    1. Check if a prophylactic antiemetic was given.

    2. Combination antiemetic therapy—5-HT3 antagonist plus dexamethasone and/or droperidol.

    3. Consider other drugs (see above).

Drugs available for the prophylaxis and treatment of PONV



Dose, route, and frequency

Number needed to treat

Side effects

Other points

Hyoscine hydrobromide


0.2–0.4mg SC or IM 6-hourly


Dry mouth, blurred vision, dizziness, confusion (elderly)

Useful for motion sickness, labyrinth disorders, posterior fossa surgery, opioid-related nausea



50mg PO, IM, or IV 8-hourly


Sedation, dry mouth, blurred vision. Tachycardia and hypotension when given IV

Useful for motion sickness, labyrinth disorders, opioid-related nausea


D2 antagonist

12.5mg IM 3mg buccal 6-hourly

Extrapyramidal, sedation

Useful for opioid-related nausea


D2 antagonist

10mg IM or IV

Extrapyramidal, sedation, abdominal cramping, dizziness

Promotes gastric emptying, ↑ lower oesophageal sphincter barrier pressure. Useful for opioid-related nausea


D2 antagonist

0.5–1.25mg IV 2.5–5mg PO 8-hourly


Extrapyramidal, sedation, neurolepsis, GI disturbances, abnormal LFTs

Used in technique of neurolept analgesia


5-HT3 antagonist

1–8mg PO, IM, or IV 8-hourly


Hypersensitivity reactions, headache, dizziness, transient elevated liver enzymes

Paediatrics—drug of first choice due to its reduced side-effect profile (0.1mg/kg)


5-HT3 antagonist

1mg IV 12-hourly

Hypersensitivity reactions, transient elevated liver enzymes


5-HT3 antagonist

2mg IV 24-hourly

6.7 (nausea) 5 (vomiting)

Hypersensitivity reactions, headache, dizziness, abdominal pain


5-HT3 antagonist


Single dose

Headache, dizziness, hypersensitivity reactions

Recently licensed in the USA for PONV



6–10mg IV Single prophylactic dose


Wound infection, adrenal suppression

Better in combination with other drugs

Further reading

Diemunsch P, Joshi GP, Brichant J-F (2009). Neurokinin-1 receptor antagonists in the prevention of postoperative nausea and vomiting. British Journal of Anaesthesia, 103, 7–13.

Gan TJ, Meyer T, Apfel CC, Chung F, Davis PJ, Eubanks S, et al. (2003). Consensus guidelines for managing postoperative nausea and vomiting. Anesthesia and Analgesia, 97, 62–71.

Gan TJ, Meyer TA, Apfel CC, Chung F, Davis PJ, Habib AS, et al. (2007). Society for Ambulatory Anesthesia guidelines for the management of postoperative nausea and vomiting. Anesthesia and Analgesia, 105, 1615–1628.

Habib AS, Gan TJ (2004). Evidence based management of postoperative nausea and vomiting: a review. Canadian Journal of Anesthesia, 51, 326–341.