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Management of Adult Postoperative Nausea and Vomiting (PONV)

PONV incidence and significance

Nausea and vomiting in the post-operative period is common and occurs in up to 80% of some patient groups. PONV can be highly distressing and many patients are more concerned about PONV than pain. It may cause significant morbidity.

Preoperatively anaesthetists aim to identify patients at high risk for PONV and give multimodal antiemetic prophylaxis/treatment intra-operatively.

The following information should assist ward doctors treating adult patients with PONV in the post-operative period.

Antiemetic drugs

Antiemetic drugs work principally by blocking afferent pathways between the gastrointestinal tract and the chemo-sensitive trigger zone, and between the vestibular apparatus and the vomiting centre. Several different receptor types have been identified:

Recommended approach

• First line: ondansetron 8 mg dispersible tablet PO or 4 mg IV q6h.
• Second line: cyclizine 12.5 - 25 mg IV (repeat q8h prn).

Note: Risk of sedation, especially with opioids. Use with caution in older or debilitated patients.

Other options to consider if symptoms have not improved within 20 minutes:

• Dexamethasone 4 mg IV: consider single dose (if not diabetic and if not already given intra-operatively).
• Scopoderm™ patch: 1.5 mg topical adhesive, effective for up to 72 hours with 2-4 hour latency for onset.

  Note: Metoclopramide 10 mg IV is not effective for PONV prophylaxis and even in larger doses, metoclopramide does not appear to be an effective antiemetic in this situation.

• Or discuss PONV problems with the Duty Anaesthetist (pager 8120/8212) or Acute Pain Service (pager 8114).

RMOs should:

• Use the safest, cheapest, lowest dose therapy to treat PONV.
• Not repeat doses of the same antiemetic drug (or drugs that act at the same receptor) within 6 hours.
• Consider surgical/neurological causes for PONV resistant to therapy.
• Consider other adjunctive treatments for PONV:
  • Use multimodal analgesia to lower total opioid doses
    • Regular paracetamol.
    • NSAIDs where appropriate.
    • If using IV tramadol, administer over 30 minutes (in 100 mL sodium chloride 0.9%).
• Maintain normal hydration in patients.
• Prevent/treat constipation and consider nasogastric drainage for bowel obstruction (discuss with Consultant).

Notes:

• Ondansetron by oral dispersible tablet has an oral bioavailability of ≈ 50% and is inexpensive, well-tolerated, and has proven efficacy as PONV prophylaxis.
• Dystonic reactions: excessive doses of dopamine receptor D₂ antagonists (e.g., metoclopramide, prochlorperazine, domperidone, droperidol) may cause extra-pyramidal symptoms or acute confusion. Treat with benztropine 1-2 mg IV, IM, or PO.
• QTc prolongation/polymorphic VT/other arrhythmias: many drugs (including ondansetron and droperidol) cause prolongation of the corrected QT interval. This may rarely predispose to torsades de pointes/polymorphic VT in susceptible individuals. Use with extreme caution in patients with known prolonged QT interval.

Topic Code: 35476