What is the safest and most effective anesthetic for a child with primary congenital glaucoma undergoing an exam under anesthesia?

Best Anesthetic for Examination Under Anesthesia in Primary Congenital Glaucoma

For children with primary congenital glaucoma undergoing examination under anesthesia, use sevoflurane induction followed by intravenous ketamine maintenance (2 mg/kg bolus, then 4 mg/kg/hour infusion), and measure intraocular pressure 15 minutes after discontinuing sevoflurane to obtain accurate readings that reflect awake values. 1

Anesthetic Protocol for PCG Examination

Induction Phase

• Induce anesthesia with sevoflurane 8% in oxygen:nitrous oxide (40:60) for rapid, smooth induction with minimal airway complications 2, 3
• Sevoflurane provides faster induction time and better hemodynamic stability compared to halothane, with lower incidence of coughing, breath-holding, and laryngospasm 3
• Establish intravenous access after induction 2

Maintenance Phase

• Immediately after induction, administer ketamine 2 mg/kg IV bolus, then maintain with 4 mg/kg/hour continuous infusion 1
• Discontinue sevoflurane once ketamine infusion begins 1
• This combination is critical because sevoflurane significantly lowers IOP (mean reduction of 3.68 mmHg compared to ketamine maintenance), which would lead to falsely low pressure readings and potential underdiagnosis of glaucoma 1

Timing of IOP Measurement

• Wait exactly 15 minutes after discontinuing sevoflurane before measuring IOP 1
• At 15 minutes, sevoflurane's IOP-lowering effect is fully reversed while ketamine maintains stable anesthesia 1
• IOP measurements at this timepoint remain stable until near-wakefulness and appear to reflect true awake values (mean difference only 0.28 mmHg, 95% CI -2.23 to 2.79 mmHg, p=0.826) 1
• Physiological variables return to baseline at 8 minutes, correlating with sevoflurane elimination 1

Critical Pitfalls to Avoid

Do NOT Measure IOP Too Early

• Measuring IOP immediately after sevoflurane induction yields the lowest and least accurate readings (mean IOP 5.6 mmHg during apnea after induction versus 7.4 mmHg baseline) 4
• Both sevoflurane and propofol significantly reduce IOP in children, with the greatest reduction occurring immediately post-induction 4

Alternative Maintenance Options (Less Optimal)

• If ketamine is unavailable or contraindicated, propofol with remifentanil can be used for maintenance, though this does not provide the same IOP stability as ketamine 4
• Sevoflurane maintenance with remifentanil results in significantly lower IOP during reversal compared to propofol-based techniques (p=0.001), making accurate glaucoma assessment more difficult 4
• For very short examinations (≤15 minutes), the induction dose of sevoflurane alone at low fresh gas flow (0.5 L/min) can maintain adequate anesthesia, reducing cost and environmental impact, though this is suboptimal for accurate IOP measurement 2

Remifentanil Dosing Considerations (If Used)

• For pediatric patients aged 1-12 years undergoing ophthalmic procedures, remifentanil maintenance infusion should be 0.25 mcg/kg/min (range 0.05-1.3 mcg/kg/min) when combined with volatile anesthetics 5
• An initial bolus of 1 mcg/kg over 30-60 seconds may be administered 5
• Pretreat with atropine to prevent bradycardia, particularly when combining remifentanil with propofol in pediatric patients 5

Measurement Technique

• Use Perkins applanation tonometry with the patient supine for IOP measurement 1
• Measure both eyes at the designated 15-minute timepoint 1

Safety Monitoring

• Continuously monitor heart rate, blood pressure, oxygen saturation, and end-tidal CO₂ throughout the procedure 1
• Ensure adequate depth of anesthesia to prevent patient movement during examination while maintaining hemodynamic stability 2