Postoperative nausea and vomiting

01Core principlesThe concepts and mechanisms needed to understand the subject.

Postoperative nausea and vomiting results from patient susceptibility, anaesthetic exposure, opioid use and the operation itself. It delays drinking, mobilisation and discharge and can cause wound stress, dehydration and aspiration. The fifth international consensus guideline updated its evidence surveillance through September 2024 and retains an algorithmic approach that joins risk assessment, baseline-risk reduction, prophylaxis and rescue.

The simplified adult Apfel factors are female sex, a history of PONV or motion sickness, non-smoking status and postoperative opioid use. Risk scores guide consistency rather than predict an individual with certainty. Procedure duration and type, volatile anaesthesia, nitrous oxide exposure and opioid requirement add context. Children need separate postoperative-vomiting models.

Prevention combines modifiable baseline measures with antiemetics. Propofol TIVA, avoiding unnecessary volatile and nitrous oxide exposure, adequate hydration and opioid-sparing regional or multimodal analgesia can reduce risk. The 2026 fifth consensus guideline recommends two prophylactic interventions for adults at any risk, provided contraindications and interactions are considered.

Breakthrough symptoms require a diagnostic pause. Hypotension, hypoglycaemia, severe pain, swallowed blood, opioid excess, ileus and surgical or neurological complications can cause nausea. When prophylaxis has failed, use a different agent or pharmacological class. Redosing the same class within six hours usually offers no benefit; long-acting drugs should not be casually repeated.

Key points

Estimate adult PONV risk from prior PONV or motion sickness, female sex, non-smoking status and expected postoperative opioid use, then account for procedure and anaesthetic factors.
Reduce baseline risk with opioid-sparing multimodal analgesia, hydration, regional techniques where suitable and propofol total intravenous anaesthesia when clinically appropriate.
Current fifth consensus guidance supports at least two prophylactic interventions for adults at any risk, selected for different mechanisms, timing, contraindications and duration.
If PONV occurs despite prophylaxis, first assess reversible or dangerous causes, then choose rapid rescue from a different agent or class rather than repeating a recent failed drug.
Reassess fluid balance, pain, opioids, blood pressure, glucose, bowel function and surgical findings; nausea is a symptom, not always an isolated anaesthetic side effect.
For day surgery, ensure oral tolerance, symptom control and a post-discharge plan because nausea and vomiting may recur after leaving immediate care.

02Mechanisms and patternsImportant relationships and how to distinguish them.

Adult susceptibility

Prior PONV or motion sickness, female sex, non-smoking and postoperative opioid exposure form the common simplified adult risk score.

Early PONV

Nausea, retching or vomiting in PACU may delay oral intake and discharge and should trigger symptom treatment plus a cause review.

Aspiration dangerRed flag

Vomiting with reduced airway reflexes, weak cough or hypoxaemia requires immediate airway positioning, suction and escalation.

Surgical causeRed flag

Distension, peritonism, escalating pain, haemodynamic change or absent gastrointestinal recovery suggests more than uncomplicated PONV.

Drug adverse effect

Sedation, hypotension, extrapyramidal symptoms, anticholinergic effects and QT prolongation can follow particular antiemetics.

Post-discharge recurrence

Nausea after ambulatory surgery may emerge after discharge when intravenous rescue and direct clinical observation are unavailable.

Red flags requiring action

Reduced consciousness with active vomiting creates an immediate aspiration risk and requires airway positioning, suction and senior airway help.
Vomiting with abdominal distension, peritonism, absent output or severe escalating pain may indicate ileus, obstruction, leak or another surgical complication.
Haematemesis, shock, new hypoxaemia, chest pain or neurological deterioration needs urgent cause-directed assessment rather than serial antiemetics.
Breakthrough PONV after prophylaxis should be treated with a different agent or pharmacological class; immediate redosing of the failed class adds little benefit.
QT prolongation, Parkinsonism, extrapyramidal risk, glaucoma, pregnancy, diabetes and drug interactions alter antiemetic selection.
Adult risk models and prophylactic regimens should not be applied directly to children; paediatric postoperative vomiting has separate prediction and treatment guidance.

03Interpreting evidenceInformation, measurements and their limitations.

Reasoning sequence

Consider the information, its meaning and its limitations before deciding what follows.

01
Structured PONV risk assessment
Why
Identify susceptibility and select preventive intensity before anaesthesia.
Interpretation and limitations
Use the score to support a protocol while considering operation and anaesthetic exposure; it is less reliable if adult predictors are applied to children.
02
Medication and anaesthetic record
Why
Identify prophylaxis already given, its timing and mechanisms, opioid burden and emetogenic exposures.
Interpretation and limitations
A failed recent class should generally not be repeated within six hours; choose a different rescue mechanism and respect long-acting drug duration.
03
Bedside physiological assessment
Why
Detect hypovolaemia, hypotension, hypoxia, pain, opioid toxicity or metabolic disturbance.
Interpretation and limitations
Abnormal physiology is treated with the symptom; preserved observations do not exclude ileus or a developing surgical complication.
04
Focused abdominal and neurological examination
Why
Distinguish routine PONV from obstruction, leak, bleeding or intracranial disease.
Interpretation and limitations
Peritonism, distension, focal neurology, severe headache or deterioration prompts urgent specialty assessment and targeted imaging or laboratory work.
05
Electrocardiogram when QT risk matters
Why
Assess repolarisation risk before or after QT-prolonging antiemetics in a susceptible patient.
Interpretation and limitations
Correct electrolyte disturbance and avoid stacking QT-prolonging agents when the interval or clinical context is concerning.

04Applied reasoningWorked examples connecting principles to decisions.

01Worked case: preventionHigh-risk adult having laparoscopic surgeryA non-smoking adult woman with previous motion sickness expects postoperative opioid treatment after laparoscopic surgery.

1Record the adult risk factors and review procedure, anaesthetic, comorbidity and medicine contraindications before selecting prophylaxis.
2Reduce baseline risk with opioid-sparing multimodal analgesia, adequate hydration and a propofol-based technique where appropriate for the whole anaesthetic plan.
3Give at least two appropriately timed prophylactic interventions with different mechanisms under the local formulary, checking glucose, QT and other patient-specific cautions.
4At handover state exactly what was given and when so that recovery staff can choose an effective different-class rescue if symptoms break through.

02Breakthrough treatmentVomiting despite ondansetron prophylaxisAn adult vomits in PACU one hour after receiving ondansetron near the end of surgery.

1Protect the airway and assess observations, pain, opioid exposure, fluid status, glucose and surgical findings for reversible or dangerous causes.
2Choose a rapid-onset antiemetic from a different agent or class after checking contraindications; do not simply repeat ondansetron or another 5-HT3 drug at one hour.
3Reassess response and adverse effects, replace fluid and electrolytes when needed, and escalate persistent or atypical symptoms for diagnostic review.

03Discharge planningNausea after ambulatory anaesthesiaSymptoms have improved but the adult remains at risk of post-discharge nausea and vomiting.

1Confirm adequate airway recovery, oral fluid tolerance, pain control, mobilisation and absence of a concerning surgical cause before discharge.
2Provide instructions on prescribed rescue medicine, hydration, opioid minimisation and when vomiting or associated symptoms require urgent contact.
3For high post-discharge risk, follow the local protocol for a suitable long-acting or oral strategy and ensure a responsible adult and contact route are available.

05Relevant medicines and safetySpecific regimens and precautions where medicines are relevant.

Blocks 5-HT3 receptors and is effective particularly for prevention of postoperative vomiting.

Ondansetron

A common adult prophylactic dose is 4 mg intravenous near the end of surgery under the local formulary.

Consider QT prolongation and interactions; after recent prophylactic failure, immediate same-class redosing is unlikely to help.

Provides a mechanistically distinct component of multimodal PONV prevention with a long clinical duration.

Dexamethasone

Give the locally approved adult prophylactic dose, commonly 4–8 mg intravenous near induction.

Consider perioperative glucose, infection context and individual risk; it is not usually repeated as rapid PACU rescue.

Provides dopamine-antagonist antiemetic activity distinct from 5-HT3 receptor blockade.

Droperidol

Use a low adult prophylactic or rescue dose from the current local protocol after reviewing the ECG risk.

QT prolongation and sedation matter, and availability or governance differs by institution; do not copy a non-UK product regimen blindly.

06Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.

Record episodes of nausea, retching and vomiting alongside prophylaxis, rescue drugs, time, response and adverse effects.
Trend oral tolerance, fluid input and losses, blood pressure, glucose when relevant, pain and opioid consumption.
Re-examine persistent or changing symptoms for aspiration, abdominal complication, bleeding, neurological change or medicine toxicity.
After rescue, observe sedation, extrapyramidal features, QT-related risk and whether symptoms recur before discharge.
For ambulatory patients, communicate post-discharge rescue instructions and a route for urgent review if oral intake fails.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Risk tools aid delivery

A score mainly helps teams apply a prevention protocol reliably; it does not remove the need to assess anaesthetic and surgical context.

Mechanism informs rescue

Knowing what prophylaxis was already given prevents ineffective immediate repetition and supports a different pharmacological approach.

Prevention includes technique

Reducing volatile exposure and opioid requirement can matter as much as adding another antiemetic to an otherwise emetogenic plan.

Nausea may be diagnostic

An antiemetic response does not exclude ileus, bleeding, myocardial ischaemia or intracranial disease when other findings are concerning.

Paediatric rules differ

Children have different risk models and drug dosing, so the adult Apfel framework must not be used as a paediatric treatment protocol.

08Common pitfallsFrequent interpretation and management errors.

01
Failing to document which prophylactic agents were given and then repeating the same class in recovery.
02
Treating persistent vomiting without examining for aspiration, ileus, obstruction, bleeding or neurological deterioration.
03
Using a single antiemetic despite a current protocol that recommends multimodal adult prophylaxis.
04
Ignoring QT, glucose, extrapyramidal and sedative risks when stacking several agents.
05
Applying adult risk factors and fixed doses directly to a child.
06
Discharging before oral tolerance and symptom trajectory are adequate or without contact instructions.

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