Are nausea and vomiting after general anesthesia considered a complication or a side effect?

Nausea and Vomiting After General Anesthesia: Side Effect, Not Complication

Postoperative nausea and vomiting (PONV) is considered a side effect rather than a complication of general anesthesia. This classification is based on its predictable nature, high incidence, and the availability of preventive measures that can be implemented based on risk assessment.

Evidence Supporting Classification as a Side Effect

Incidence and Predictability

• PONV is extremely common, occurring in approximately 30% of all surgical patients and up to 80% in high-risk populations 1
• The predictable nature of PONV is demonstrated by validated risk assessment tools (like the Apfel score) that can identify patients at higher risk 2

Recognition in Guidelines

• The Enhanced Recovery After Surgery (ERAS) Society guidelines specifically categorize nausea and vomiting as common symptoms experienced after cesarean delivery under general anesthesia, not as complications 1
• Guidelines consistently refer to PONV as a "side effect" when discussing preventive strategies 1

Preventability Through Risk Reduction

• Multiple guidelines recommend prophylactic measures for PONV based on risk assessment, indicating it's an anticipated side effect that can be mitigated 1
• The FDA labeling for ondansetron specifically indicates its use for "prevention of postoperative nausea and vomiting," positioning PONV as a predictable side effect requiring prophylaxis 3

Distinguishing Side Effects from Complications

Side Effects (Like PONV):

• Expected, predictable responses to medications or procedures
• Generally self-limiting
• High incidence (PONV occurs in 21-79% of patients under regional anesthesia for cesarean delivery) 1
• Can be anticipated and prevented with prophylactic measures
• Typically resolve without permanent sequelae

Complications:

• Unexpected adverse events
• Often more severe in nature
• Lower incidence
• May require significant intervention
• Can lead to prolonged hospitalization or permanent harm

Clinical Implications of This Classification

1. Risk Assessment: Patients should be evaluated for PONV risk factors preoperatively

   • Female gender
   • Non-smoking status
   • History of PONV or motion sickness
   • Expected postoperative opioid use

2. Prophylactic Approach: For patients with risk factors, preventive measures should be implemented:

   • Multimodal antiemetic therapy based on risk level 1, 4
   • Adequate hydration (mildly positive fluid balance) 1
   • Consider total intravenous anesthesia rather than inhalational agents when possible 2

3. Medication Selection:

   • High-quality evidence supports several antiemetics for PONV prevention:
     • 5-HT3 antagonists (ondansetron, granisetron, ramosetron)
     • NK1 receptor antagonists (aprepitant, fosaprepitant)
     • Corticosteroids (dexamethasone)
     • D2 receptor antagonists (droperidol) 4, 5

Practical Management Considerations

• Fluid Management: A mildly positive fluid balance reduces PONV incidence by preventing splanchnic hypoperfusion 1
• Non-pharmacological Approaches: Consider acupressure at P6 point as an adjunct (23% vs 41% PONV in treatment vs control) 6
• Combination Therapy: Multiple antiemetics with different mechanisms of action are more effective than monotherapy for high-risk patients 7, 5

While PONV can negatively impact patient satisfaction and potentially lead to complications like dehydration or aspiration if severe, its predictable nature, high incidence, and preventability firmly establish it as a side effect rather than a complication of general anesthesia.