Post-operative Nausea and Vomiting (PONV)

Overview

Post-operative Nausea and Vomiting is the leading cause of delayed discharge from PACU. Current recommendations is at least 2 prophylactic drugs for patients with at least 1 risk factor for PONV. Combinations should be with drugs that have different mechanism of action.

Chemoreceptor Trigger Zone

Major Risk Factors for PONV

• Risk factors for PONV in adults
  • Age < 50 years
  • Female gender
  • History of PONV/Motion sickness
  • Non-smoking status
• Risk factors for PONV in children
  • Age > 3 years
  • History of nausea/vomiting (in the child or relative)
  • Strabismus surgery
  • Surgery > 30 minutes
• Factors that increase the incidence of PONV
  • Duration of anaesthesia
  • Post-operative opioid use
  • Laparoscopic, cholecystectomy, gynaecological
  • Nitrous oxide and volatile agents
• Strategies for reducing PONV
  • Regional anaesthesia
  • Using propofol for induction and maintenance of anaesthesia (TIVA)
  • Avoid nitrous oxide and volatile agents
  • Minimising intra-operative and post-operative opioids use
  • Adequate hydration
  • Avoid hypotension and cerebral hypoxia
  • Use a combination of antiemetics in different classes
  • Use sugammadex instead of neostigmine for reversal
• Consequences of PONV
  • Aspiration risk and airway compromise
  • Dehydration and electrolyte changes
  • Increased CVP, ICP, suture or mesh disruption, venous hypertension and bleeding, or wound dehiscence

Antiemetics

5-HT3 Antagonists (Ondansetron, Granisetron)

These are more effective at preventing emesis than just preventing nausea. They are usually given approximately 30 minutes before emergence

• Side effects of 5-HT3 Antagonists
  • Headache
  • QT prolongation

Steroids (Dexamethasone)

Steroids are cheap and effective and give prolonged PONV relief. There mechanism of action is uncertain. Dexamethasone (4 -10mg) can be given IV after induction.

• Side effects
  • Can cause severe perineal itching or discomfort in awake patients
  • A single does does not cause a significant increase in blood glucose (for diabetes), infection, or cancer recurrence

IV Induction agents (Propofol)

Propofol can be given as a low-dose bolus (10-20 mg) in PACU or as low-dose infusion during the case to prevent PONV.

Anticholinergics (Scopolamine patch)

Scopolamine patch can be given 2-4 hours pre-op. A patch (1.5 mg) can also be given TD q72h (placed in the posterior ear lobe)

• Side effects
  • Anticholinergic side effects are potentially worse than nausea and vomiting in some patients
  • Can cause post-op confusion/delirium in elderly patients
  • Mydriasis if the patient touches the patch and wipes their eyes

Phenothiazines (Promethazine, Prochlorperazine)

These are dopamine antagonists (promethazine also has H1 antagonism). They can be given IV or IM. Usually given IV at the end of a case.

• Side effects
  • Sedation
  • Extrapyramidal side effects

Gastrokinetic (Metoclopramide)

Metoclopromide is a dopamine antagonist. Dose required may exceed 25 mg which can increase the risk of extrapyramidal side effects.

• Side effects
  • Extrapyramidal side effects
  • Increased GI motility and LES tone (avoid in patients with bowel obstruction)
• Contraindications
  • Patients with Parkinson Disease
  • Bowel obstruction

Butyrophenones (Droperidol, Haloperidol)

These are central dopamine anatagonist. Droperidol is especially cheap and very effective, however it can cause arrhythmia when given at much higher doses. Haloperidol (at 1mg) is just as effective as Ondansetron with a similar side effect profile.

• Side effects
  • QT prolongation
• Contraindications
  • Patients with Parkinson Disease

Substance P Antagonists (Aprepitant, Fosaprepitant)

These are Neurkinin 1 Receptor Antagonists. They are more effective when given with Ondansetron. The downside is that they are expensive (reserved for posterior fossa neurosurgery and chemotherapy related PONV). PO is preferred since it is more cost effective. The can also be used for patients with refractory PONV.

Other Antiemetic Agents