Synopsis
Identify the dominant nausea mechanism and reversible emergencies, restore a reliable medicine route, choose one mechanism-matched antiemetic with explicit safety checks, and review symptom relief, hydration, nutrition and adverse effects against the person's goals.
- First-line history defines nausea versus retching or vomiting, volume and content, relation to food, movement, medicines, bowels, headache and abdominal pain.
- Examine hydration, mouth, abdomen, bowel sounds, rectum when indicated, neurology, vestibular signs and current patches, pumps and medicines.
- Treat the cause when useful: constipation, obstruction, infection, hypercalcaemia, uraemia, gastric stasis, raised intracranial pressure and medicine toxicity need different interventions.
- Choose the first antiemetic by dominant mechanism rather than prescribing several empirically: prokinetic, dopamine antagonist, antihistamine-antimuscarinic or serotonin antagonist each has a different role.
- Metoclopramide is first-line for gastric stasis or partial obstruction without colic, but avoid it in complete mechanical obstruction, perforation, Parkinson's disease and previous dystonia.
- Haloperidol can help chemically mediated nausea from opioids or organ failure; use low doses and review Parkinson, Lewy-body, QT and extrapyramidal risk.
- Cyclizine can help vestibular or raised-pressure nausea and complete obstruction but adds anticholinergic effects and can oppose a prokinetic when combined without rationale.
- Switch to subcutaneous, buccal, rectal or transdermal routes when vomiting makes oral absorption unreliable and reconcile essential medicines at the same time.
- The gold-standard plan states the presumed mechanism, first medicine, rescue, route, response time, adverse-effect checks and a second-line strategy if the formulation is wrong.
Key red flags
Colicky pain, distension, constipation or obstipation and faeculent vomiting suggests mechanical bowel obstruction and makes routine prokinetic treatment unsafe in complete obstruction.
Rigid abdomen, rebound, fever, lactate rise or haemodynamic instability suggests perforation, ischaemia or peritonitis and requires urgent surgical assessment.
Haematemesis, coffee-ground material, melaena, syncope or anticoagulant exposure requires acute gastrointestinal-bleeding management.
Progressive morning headache, projectile vomiting, focal neurology, seizure or altered consciousness suggests raised intracranial pressure.
Polyuria, dehydration, constipation, confusion or arrhythmia may indicate hypercalcaemia and needs urgent calcium and renal assessment.
Repeated vomiting with poor urine output, postural hypotension or marked electrolyte disturbance threatens renal injury, delirium and arrhythmia.
New dystonia, akathisia, rigidity, QT symptoms or profound sedation after antiemetic therapy requires immediate medicine review.
Drowsiness, bulbar dysfunction, cough failure or active large-volume vomiting threatens airway contamination and requires immediate positioning and support.
Investigation priorities
Link symptoms with meals, bowel function, movement, medicines, headache, pain, treatment and vomiting content and timing.
Management branches
Nausea or vomiting is new, changed or inadequately controlled.
- Identify emergency features, assess hydration and aspiration, examine abdomen and neurology and reconcile bowel pattern, medicines and essential oral treatment.
- Treat reversible contributors and choose one antiemetic whose receptor and motility action fits the dominant mechanism and organ-function risks.
- Use a reliable route, prescribe rescue and review within the drug's onset window, documenting response, toxicity and the next branch if symptoms persist.