What are the multimodal strategies for preventing postoperative nausea and vomiting (PONV) in strabismus surgery?

Multimodal PONV Prevention for Strabismus Surgery

For strabismus surgery, administer combination prophylaxis with dexamethasone 150 mcg/kg plus ondansetron 75 mcg/kg intravenously, as this reduces PONV incidence to approximately 5% compared to 23% with dexamethasone alone or 83% with placebo. 1, 2

Risk Assessment

Strabismus surgery represents an exceptionally high-risk procedure for PONV, with baseline incidence reaching 83% without prophylaxis 2. Key risk factors include:

• Surgical factors: Extraocular muscle manipulation triggers vagal reflexes and releases serotonin 2
• Patient demographics: Predominantly pediatric population (ages 2-12 years), with female patients at higher risk 3, 2
• Anesthetic factors: Volatile anesthetics (halothane, sevoflurane) and nitrous oxide increase risk 2, 4

Core Pharmacologic Strategy

Primary Combination Therapy

Administer both agents at induction or immediately following anesthesia induction 1, 2:

• Dexamethasone: 150 mcg/kg IV (maximum dose typically 8-10 mg) 1
• Ondansetron: 75 mcg/kg IV (maximum 4 mg for patients >40 kg) 3, 2

The evidence strongly supports this specific combination. A randomized trial in 193 pediatric strabismus patients demonstrated PONV incidence of 5% with dexamethasone plus ondansetron versus 23% with dexamethasone alone (P<0.001) 1. The 75 mcg/kg ondansetron dose provides equivalent efficacy to higher doses (100-150 mcg/kg) with better cost-effectiveness 2.

Dose-Response Evidence

Ondansetron demonstrates clear dose-response relationship in strabismus surgery 2:

• 25 mcg/kg: 77% PONV incidence (not significantly different from placebo)
• 50 mcg/kg: 47% incidence
• 75 mcg/kg: 30% incidence (optimal dose)
• 100-150 mcg/kg: 27-30% incidence (no additional benefit)

Critical pitfall: Underdosing ondansetron below 75 mcg/kg significantly reduces efficacy, while doses above 75 mcg/kg provide no additional benefit but increase cost 2.

Anesthetic Technique Modifications

Induction and Maintenance

Use propofol-based total intravenous anesthesia (TIVA) when feasible, avoiding volatile anesthetics and nitrous oxide 5:

• Propofol 2.5-3.5 mg/kg for induction is acceptable 1
• TIVA with propofol maintenance reduces PONV severity compared to volatile-based anesthesia 5
• If volatile agents must be used, minimize exposure duration 2, 4

Opioid-Sparing Strategies

Minimize intraoperative and postoperative opioid use through multimodal analgesia 5:

• Acetaminophen (paracetamol) 15 mg/kg IV or PO as baseline 6
• Consider ketorolac 0.5 mg/kg IV (maximum 30 mg) if not contraindicated 7
• Local anesthetic infiltration at surgical site when appropriate 7

Each reduction in opioid exposure decreases PONV risk, as opioids are independent risk factors for nausea and vomiting 5.

Fluid Management

Administer adequate intravenous crystalloid fluids to maintain normovolemia and prevent hypovolemia-induced PONV 5:

• Target mildly positive fluid balance (approximately 2 mL/kg/h minimum) 5
• Hypovolemia causes splanchnic hypoperfusion, increasing intestinal serotonin release and triggering PONV 5
• Avoid fluid overload, which paradoxically increases PONV through other mechanisms 5

Quality Improvement Bundle Approach

A 4-year quality improvement initiative in pediatric strabismus surgery reduced PONV from 18% to 4.72% using a standardized bundle 4:

1. Mandatory risk assessment for all patients 4
2. Standardized dual antiemetic prophylaxis (dexamethasone + ondansetron) 4
3. Anesthetic technique optimization (minimize volatiles, reduce opioids) 4
4. Adequate hydration protocols 4
5. Regular audit and feedback to maintain compliance 8, 4

Bundle compliance monitoring is essential—institutions with continuous quality improvement programs and quarterly feedback sessions maintain lower PONV rates over time 8, 4.

Rescue Therapy

For patients who develop PONV despite prophylaxis, administer a different class of antiemetic 9, 10:

• First-line rescue: Ondansetron 0.1 mg/kg IV (if not used prophylactically) or metoclopramide 0.1-0.15 mg/kg IV 3, 11
• Second-line rescue: Consider olanzapine 2.5-5 mg PO/SL for refractory cases in older children/adolescents (≥3 Apfel risk factors) 10
• Avoid repeat dosing of the same prophylactic agent within 6 hours, as efficacy is limited 3

Critical pitfall: Administering a second dose of ondansetron postoperatively in patients who received prophylactic ondansetron does not provide additional PONV control 3.

Additional Considerations

Neuromuscular Blockade Reversal

Use sugammadex for neuromuscular blockade reversal rather than neostigmine when available 5:

• Neostigmine increases PONV risk through cholinergic effects 5
• Sugammadex (selective relaxant binding agent) does not increase PONV 5

Temperature Management

Maintain normothermia throughout the perioperative period 5:

• Hypothermia independently increases PONV risk 5
• Use active warming devices and warmed IV fluids 5

Timing of Antiemetic Administration

Administer dexamethasone at or immediately after induction, and ondansetron near the end of surgery or at induction 1, 2:

• Dexamethasone requires 1-2 hours for peak effect, so early administration is optimal 1
• Ondansetron has rapid onset and can be given at induction or toward end of procedure 2