Postoperative nausea and vomiting

What is PONV and why it matters

• PONV = nausea and/or vomiting occurring after surgery/anaesthesia (often within the first 24 hours).
• Common, distressing, and a frequent cause of delayed discharge and unplanned admission.
• Can cause dehydration, electrolyte disturbance, wound dehiscence, bleeding, aspiration, and severe discomfort.
• Treat early: nausea is easier to control than established vomiting.

Core physiology (simple model)

• Vomiting is coordinated by brainstem pathways receiving input from multiple sites.
• Key trigger areas: gut (vagal afferents), vestibular system (motion), higher centres (anxiety/pain), and chemoreceptor trigger zone (blood-borne drugs/toxins).
• Different antiemetics work at different receptors; combining different classes improves efficacy.

Who is at risk (quick bedside assessment)

• Patient factors: female sex, non-smoker, history of PONV or motion sickness.
• Anaesthetic factors: volatile agents, nitrous oxide, perioperative opioids.
• Surgical factors: longer duration; higher risk with laparoscopic, gynaecological, ENT/strabismus, and some abdominal surgery.
• Practical approach: if multiple risk factors present, plan multimodal prophylaxis.

Prevention: general measures (often overlooked)

• Minimise opioids: use multimodal analgesia (paracetamol, NSAID if appropriate, regional/neuraxial techniques).
• Consider TIVA with propofol for higher-risk patients (reduces PONV compared with volatiles).
• Avoid nitrous oxide where possible in high-risk cases.
• Maintain hydration and treat hypotension; uncontrolled pain increases nausea.
• Consider gastric decompression if significant gastric insufflation (e.g., mask ventilation, laparoscopy).

Antiemetic prophylaxis: common first-line options

• Use 1 agent for low risk; 2 agents from different classes for moderate risk; 3+ strategies for high risk (including anaesthetic technique).
• Dexamethasone 4 mg IV (typical adult dose) early in case (after induction): effective and cheap; avoid if significant concern about hyperglycaemia/infection risk—use clinical judgement.
• 5-HT3 antagonist (e.g., ondansetron 4 mg IV) usually near end of surgery: good for established nausea too.
• Droperidol 0.625–1.25 mg IV (where used locally): effective; be mindful of QT prolongation risk and local policy/monitoring.
• Cyclizine 50 mg IV/IM: useful, especially vestibular component; can be sedating and anticholinergic (dry mouth).
• Metoclopramide 10 mg IV: modest efficacy for PONV; consider if gastric stasis suspected; avoid in Parkinson’s disease and use caution with extrapyramidal side effects.

Treatment in PACU/ward: stepwise approach

• First: assess and fix contributors—pain, hypotension, hypoxia, hypercarbia, full stomach/ileus, opioid boluses, blood in pharynx, motion, anxiety.
• If prophylaxis was given: treat with an antiemetic from a DIFFERENT class than already used.
• If no prophylaxis: give a first-line agent (often ondansetron 4 mg IV) and reassess.
• If ongoing symptoms: add a second agent from another class (e.g., dexamethasone if not already given, droperidol, cyclizine).
• Persistent/refractory PONV: consider third-line options per local guideline (e.g., low-dose propofol in PACU, NK1 antagonist where available) and seek senior review.
• Reassess response and document what was given and when (avoid repeating same class too soon).

Special situations new starters commonly meet

• Day-case surgery: PONV is a common reason for delayed discharge—be proactive with prophylaxis in at-risk patients.
• Laparoscopy: higher risk; consider TIVA, dexamethasone + ondansetron, opioid-sparing analgesia.
• ENT/tonsil surgery: blood swallowed can trigger vomiting; ensure good suctioning and consider prophylaxis.
• Opioid-related nausea: reduce/stop opioid if possible; use alternatives and consider small-dose naloxone infusion only with senior guidance and local protocol.
• QT prolongation risk: avoid/limit QT-prolonging antiemetics (e.g., droperidol, ondansetron) if significant QTc prolongation or multiple QT-prolonging drugs—seek senior advice and follow local policy.

Safety, documentation, and communication

• Record PONV risk factors, prophylaxis given (drug, dose, time), and response to treatment.
• Handover to PACU/ward: what was used, what to avoid repeating, and next-step plan if nausea recurs.
• Check allergies, pregnancy status where relevant, and drug interactions (especially QT-prolonging combinations).
• Always consider aspiration risk in actively vomiting patients: positioning, suction, oxygen, and escalate early.