Anaesthesia for Vitreoretinal Surgery

Quick Answer

Exam Essentials - ANZCA Final Examination

Vitreoretinal Surgery Types: Pars plana vitrectomy (PPV), scleral buckling, pneumatic retinopexy, and combined procedures. Duration: 1-4 hours depending on complexity. Anaesthetic options: General anaesthesia (most common), local with sedation (selected cases), sub-Tenon's (increasingly used) [1-3].

Key Anaesthetic Considerations:

• Nitrous oxide contraindicated with intraocular gas: SF6, C3F8 expand with N2O; stop N2O ≥15 minutes before gas injection [4,5]
• Patient immobility: Critical for microscopic surgery; no head movement
• Oculocardiac reflex: Common during scleral buckle and muscle manipulation (30-40% incidence) [6,7]
• Positioning: Supine with head turned; secure head fixation; avoid pressure on eyes
• Temperature management: Long cases require active warming [8,9]

Gas Tamponade Agents:

• Air: Resolves in 5-7 days; no N2O restrictions
• SF6 (sulfur hexafluoride): 2× expansion in 24-48h, lasts 10-14 days; N2O contraindicated
• C3F8 (perfluoropropane): 4× expansion in 72h, lasts 55-65 days; N2O contraindicated; air travel contraindicated [10,11]

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Populations

Epidemiology of Vitreoretinal Disease:

Aboriginal and Torres Strait Islander populations experience distinct patterns of retinal disease with significant disparities in access to vitreoretinal surgical services:

• Diabetic retinopathy: Indigenous Australians have 3-4 times higher rates of vision-threatening diabetic retinopathy, with higher prevalence of proliferative diabetic retinopathy requiring vitrectomy [12,13]
• Age-related macular degeneration: Lower rates than non-Indigenous populations but increasing with ageing demographic
• Retinal detachment: Traumatic retinal detachment more common in working-age Indigenous men due to occupational exposures (mining, agriculture) [14]

Barriers to Vitreoretinal Care:

Diabetic Retinopathy Crisis:

• Prevalence: 20-30% of Indigenous adults with diabetes have sight-threatening retinopathy
• Laser treatment rates: Lower than non-Indigenous despite higher disease burden
• Vitreoretinal surgery: Required for tractional retinal detachment, vitreous haemorrhage not clearing
• Outcomes: Often present late with poor baseline vision; visual outcomes worse than early intervention cases [18,19]

Cultural Safety in Surgical Care:

1. Communication: Complex procedures require detailed explanation; Aboriginal Health Workers essential for translation and cultural context
2. Family involvement: Extended family may need to understand procedure and postoperative requirements
3. Positioning support: Face-down positioning for 1-2 weeks is culturally challenging; may require temporary relocation or community support
4. Postoperative care: Partnership with Aboriginal Community Controlled Health Services for wound monitoring and complication detection [20,21]

Māori Populations (Aotearoa New Zealand)

Epidemiological Profile:

Māori populations show similar disparities in diabetic eye disease and vitreoretinal surgical access:

• Diabetic retinopathy: 2-3 times higher prevalence than European New Zealanders; earlier onset
• Vitreoretinal surgery rates: Lower utilisation despite higher disease burden
• Trauma-related detachments: Higher rates in young Māori men (sports, occupational injuries) [22,23]

Structural Barriers:

• Specialist distribution: Vitreoretinal services concentrated in Auckland, Wellington, Christchurch
• Northland and Midland regions: Limited access requiring inter-regional transfers
• Socioeconomic factors: Cost barriers for private surgery; long public waiting lists [24,25]

Te Tiriti o Waitangi Considerations:

1. Equity of access: Proactive identification and referral pathways for Māori with diabetic eye disease
2. Whānau-centred care: Family involvement in understanding complex surgery and postoperative care
3. Kaupapa Māori approaches: Māori Health Workers supporting patients through surgical journey
4. Cultural advisors: Guidance on appropriate communication and support strategies [26,27]

Postoperative Positioning Challenges:

• Face-down positioning for macular hole surgery particularly challenging
• Whānau support networks may assist with positioning compliance
• Community health workers can monitor for postoperative complications
• Transport and accommodation support for follow-up appointments [28,29]

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Epidemiology and Surgical Indications

Global Burden of Vitreoretinal Disease

Retinal Detachment:

• Incidence: 6.3-17.9 per 100,000 person-years [30]
• Age: Bimodal distribution (20-30 years trauma/axial myopia; 60-70 years degenerative)
• Risk factors: High myopia (>-6.00 D), previous cataract surgery, trauma, lattice degeneration
• Bilateral: 5-10% have bilateral detachment at presentation or subsequently [31,32]

Diabetic Retinopathy:

• Global prevalence: 93 million people with diabetic retinopathy; 17 million with proliferative diabetic retinopathy [33]
• Vision-threatening: 28 million with diabetic macular oedema or proliferative disease
• Vitreoretinal surgery indications: Tractional retinal detachment, non-clearing vitreous haemorrhage, severe epiretinal proliferation [34,35]

Macular Hole:

• Incidence: 3.3-8.7 per 100,000 per year [36]
• Female predominance: 3:1 ratio
• Age: Typically 60-70 years; age-related vitreomacular traction
• Bilateral: 10-20% develop hole in fellow eye [37]

Surgical Indications and Approaches

Surgical Techniques

Pars Plana Vitrectomy (PPV):

Scleral Buckle:

• Encircling band or segmental buckle to support retinal breaks
• Cryotherapy or laser for retinopexy
• Oculocardiac reflex common during muscle manipulation
• Duration 1.5-2.5 hours
• Postoperative pain, nausea more common than PPV [44,45]

Pneumatic Retinopexy:

• Office-based or minor OT procedure
• Intravitreal gas injection (C3F8 or SF6)
• Cryotherapy or laser for retinopexy
• Postoperative positioning critical
• Can be done under topical ± sedation [46,47]

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Anaesthetic Management

General Anaesthesia Technique

Induction:

Maintenance:

Emergence:

• Deep extubation preferred to prevent coughing/bucking
• Full reversal of neuromuscular blockade
• Antiemetic prophylaxis mandatory (high PONV risk)
• Smooth emergence critical to protect surgical repair

Nitrous Oxide and Intraocular Gas

Critical Interaction:

N2O is 34× more soluble in blood than nitrogen. When inhaled, it diffuses into closed gas spaces faster than nitrogen can exit, causing rapid expansion.

Consequences of N2O Use with Intraocular Gas:

• Rapid IOP rise (can exceed 80-100 mmHg)
• Central retinal artery occlusion → irreversible blindness
• Scleral rupture (extreme cases)
• Corneal decompensation [52-54]

Management Protocol:

Regional Anaesthesia Techniques

Sub-Tenon's Block:

Increasingly popular for vitreoretinal surgery:

Peribulbar Block:

• Two injections: inferior-temporal and superior-nasal
• 5-10 mL local anaesthetic mixture
• Complications: retrobulbar haemorrhage (0.5-1%), globe perforation (0.01-0.1%), optic nerve injury (rare), brainstem anaesthesia (rare) [59,60]

Retrobulbar Block:

• Sharper needle directly into muscle cone
• Higher risk profile; less commonly used now
• Same complications as peribulbar but potentially more severe [61,62]

Sedation for Local Cases:

• Light sedation only (midazolam 0.5-2 mg IV ± fentanyl 25-50 mcg)
• Patient must be able to cooperate and communicate
• Critical complication warning signs: severe pain, sudden vision loss (optic nerve injury)

Oculocardiac Reflex Management

Prevalence:

• 30-40% during scleral buckle surgery
• 10-20% during PPV with scleral buckle component
• Higher in children, anxious patients [63,64]

Prevention:

• Prophylactic atropine: 10-20 mcg/kg IV (controversial)
• Retro/peribulbar block (if used) eliminates reflex
• Adequate depth before surgical manipulation
• Gentle surgical technique [65,66]

Treatment:

1. Stop surgical stimulus immediately
2. Check depth of anaesthesia
3. Atropine 10-20 mcg/kg IV (repeat if needed)
4. Ensure adequate oxygenation
5. Resume surgery when stable [67,68]

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Postoperative Considerations

Positioning Requirements

Face-Down Positioning (Prone):

Anaesthetic Implications:

• Patient must understand and be capable of positioning
• Confusion/delirium may compromise positioning
• Respiratory compromise in prone position (obesity, COPD)
• Pressure injuries (face, breasts, knees)
• VTE prophylaxis important [69,70]

Positioning Aids:

• Face-down pillows with mirror for viewing
• Prone positioning chairs/tables
• Supportive cushions for comfort
• Patient education and written instructions critical

Pain Management

Scleral Buckle:

• More painful than PPV (scleral sutures, muscle manipulation)
• Multimodal analgesia:
  • Paracetamol 1 g q6h regular
  • NSAIDs (ibuprofen 400 mg q8h) if no contraindication
  • Topical anaesthetic drops (limited use)
  • Opioids (codeine or oxycodone) if severe pain
• Ice packs to reduce swelling [71,72]

PPV:

• Generally mild discomfort
• Paracetamol ± NSAIDs usually sufficient
• Positioning-related discomfort common
• Gas bubble sensation (normal) [73]

Complications

Intraoperative:

Postoperative:

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SAQ Practice Questions

SAQ 1: Nitrous Oxide and Gas Tamponade (20 marks)

Scenario: A 58-year-old man is undergoing pars plana vitrectomy with gas tamponade (C3F8) for repair of retinal detachment. The procedure is expected to take 2.5 hours.

Questions:

a) Explain the interaction between nitrous oxide and intraocular gas tamponade agents. (6 marks)

b) Outline your anaesthetic management to avoid this complication. (7 marks)

c) What are the postoperative implications for this patient regarding the intraocular gas? (7 marks)

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Model Answer:

a) N2O and gas interaction (6 marks):

• Diffusion kinetics: N2O is 34× more soluble in blood than nitrogen; diffuses into air-filled spaces faster than nitrogen can exit (2 marks)
• Gas expansion: N2O enters intraocular gas bubble causing rapid volume expansion (1 mark)
• C3F8 properties: Expands 4× over 72 hours; combined with N2O can cause catastrophic IOP rise (1 mark)
• Consequences: IOP can exceed 80-100 mmHg → central retinal artery occlusion → irreversible blindness, possible scleral rupture (2 marks)

b) Anaesthetic management (7 marks):

• Preoperative planning: Confirm gas tamponade planned; document clearly (1 mark)
• No N2O from outset: Do not use N2O at any point in this case (1 mark)
• Alternative maintenance: TIVA (propofol + remifentanil) or volatile without N2O (1 mark)
• If N2O inadvertently used: Stop ≥15 minutes before gas injection; document time stopped (1 mark)
• Communication: "NO N2O" warning on anaesthetic chart; verbal handover to recovery staff (1 mark)
• Monitoring: Standard monitoring; ensure smooth emergence (1 mark)
• Patient warning: Provide gas warning card postoperatively (1 mark)

c) Postoperative implications (7 marks):

• Duration: C3F8 lasts 55-65 days; gradually resorbs (1 mark)
• Positioning: Strict head positioning required (position depends on break location) for 1-2 weeks (2 marks)
• Air travel: Absolute contraindication until gas fully resorbed; altitude causes expansion (2 marks)
• N2O avoidance: Must inform any future anaesthetic teams about intraocular gas (1 mark)
• Visual limitations: Reduced vision while gas present; slowly improves as resorbs (1 mark)

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SAQ 2: Oculocardiac Reflex (20 marks)

Scenario: During scleral buckle surgery for retinal detachment, the patient develops sudden bradycardia (heart rate drops from 72 to 38 bpm) when the surgeon places the scleral buckle and begins cryotherapy.

Questions:

a) What is the pathophysiology of the oculocardiac reflex? (6 marks)

b) Describe your immediate management of this situation. (7 marks)

c) How would you prevent recurrence during the remainder of the surgery? (7 marks)

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Model Answer:

a) Pathophysiology (6 marks):

• Reflex arc: Trigeminal nerve afferent (V1 - ophthalmic division from globe/muscles) to sensory nucleus (2 marks)
• Efferent: Vagus nerve (X) to cardiac pacemaker cells (2 marks)
• Response: Bradycardia, junctional rhythm, AV block, asystole possible (1 mark)
• Triggers: Traction on extraocular muscles, pressure on globe, scleral manipulation, cryotherapy (1 mark)

b) Immediate management (7 marks):

• Stop surgical stimulus: Ask surgeon to pause immediately (2 marks)
• Assess patient: Check BP, SpO2, ensure adequate depth of anaesthesia (1 mark)
• Atropine: 10-20 mcg/kg IV immediately (20-30 mcg/kg if severe) (2 marks)
• Oxygenation: Ensure FiO2 adequate; rule out hypoxia/hypercarbia (1 mark)
• Local block: If not already performed, consider sub-Tenon's/peribulbar block to abolish reflex (1 mark)
• Resume when stable: Wait until HR returns to baseline before continuing (1 mark)

c) Prevention strategies (7 marks):

• Adequate depth: Ensure deep anaesthesia before surgical manipulation (1 mark)
• Atropine prophylaxis: Consider 10-20 mcg/kg IV before further buckle manipulation (2 marks)
• Local anaesthesia block: Sub-Tenon's or peribulbar block eliminates afferent limb of reflex (2 marks)
• Gentle surgical technique: Request surgeon to minimise traction, apply cryotherapy in short bursts (1 mark)
• Communication: Warn surgeon about recurrence risk; monitor ECG continuously (1 mark)

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SAQ 3: Local vs General Anaesthesia (20 marks)

Scenario: A 72-year-old woman with well-controlled hypertension is scheduled for pars plana vitrectomy for epiretinal membrane peel. She expresses a strong preference for "being awake" due to concerns about general anaesthesia risks.

Questions:

a) What factors would you consider when deciding between local and general anaesthesia for this case? (6 marks)

b) Describe the technique and monitoring requirements for sub-Tenon's block. (7 marks)

c) What are the contraindications to local anaesthesia for vitrectomy? (7 marks)

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Model Answer:

a) Decision factors (6 marks):

• Patient factors: Age, cognitive function, ability to cooperate, anxiety level, comorbidities (1 mark)
• Surgical factors: Duration (epiretinal membrane typically 1-1.5 hours), complexity, need for prone positioning (1 mark)
• Airway: Ability to lie flat without respiratory compromise (1 mark)
• Communication: Ability to understand procedure and remain still (1 mark)
• Surgeon preference: Some prefer GA for complex/long cases (1 mark)
• Patient preference: Strong preference for LA if suitable candidate (1 mark)

b) Sub-Tenon's technique (7 marks):

• Preparation: Topical anaesthetic drops, lid speculum, disinfection (1 mark)
• Access: Small incision in Tenon's capsule (superior-nasal quadrant typically) with Westcott scissors (1 mark)
• Cannula insertion: Blunt curved cannula (e.g., Stevens cannula) passed along globe into posterior sub-Tenon's space (2 marks)
• Injection: 3-5 mL of 1:1 mixture lidocaine 2% and bupivacaine 0.5% ± hyaluronidase (1 mark)
• Onset: 5-10 minutes; test akinesia and anaesthesia (1 mark)
• Monitoring: Continuous pulse oximetry, NIBP, ECG; IV access; sedation if needed (1 mark)

c) Contraindications to LA (7 marks):

• Inability to cooperate: Dementia, developmental delay, severe anxiety/claustrophobia (1 mark) | Communication barriers: Language, deafness (unless interpreter available) (1 mark) | Respiratory compromise: Unable to lie flat (severe COPD, orthopnoea) (1 mark) | Long/complex surgery: >2 hours, combined procedures (1 mark) | Prone positioning required: Patient cannot self-position (1 mark) | Previous scleral buckle: Altered anatomy may make block difficult (1 mark) | Anticipated complications: High risk of suprachoroidal haemorrhage, severe PVR (1 mark)

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ANZCA Exam Focus

Viva Voce Preparation

Scenario 1: N2O and Gas Tamponade

"You discover postoperatively that a patient with intraocular C3F8 gas received nitrous oxide during a subsequent general anaesthetic. What are the implications?"

Key points:

• C3F8 + N2O causes dangerous gas expansion
• Risk of central retinal artery occlusion
• Emergency ophthalmology assessment
• IOP-lowering measures if needed
• "Gas bubble" warning cards essential
• Importance of patient education and documentation

Scenario 2: Scleral Buckle with OCR

"During scleral buckle surgery, the patient becomes profoundly bradycardic. How do you manage this?"

Key points:

• Stop surgical stimulus immediately
• Ensure adequate depth
• Atropine 10-20 mcg/kg IV
• Consider local block to abolish reflex
• Prevention for remainder of case

Scenario 3: Postoperative Positioning

"A patient with macular hole repair is struggling to maintain face-down positioning. What advice can you give?"

Key points:

• Critical for surgical success (hole closure)
• Positioning aids available (pillows, chairs)
• Family support essential
• Trade-off between strict positioning and patient tolerance
• Complications of non-compliance (failed hole closure)

Written Exam High-Yield Topics

ANZCA Professional Standards

PS07: Guidelines for Perioperative Care

• N2O safety and gas tamponade documentation requirements
• Monitoring standards for long cases
• Positioning and pressure injury prevention

PS01(G): Position Statement on Anaesthesia Care of the Elderly

• Many vitreoretinal patients elderly
• Cognitive assessment for postoperative positioning compliance
• Delirium prevention and recognition

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This document was created for educational purposes for ANZCA Fellowship examination preparation. All citations are from peer-reviewed literature. Last updated: 2026-02-03