Anaesthesia for Ophthalmic Trauma

Quick Answer

Exam Essentials - ANZCA Final Examination

Open Globe Injury: Full-thickness corneal or scleral wound with intraocular contents at risk. Anaesthetic priorities: (1) Prevent further injury by avoiding any pressure on the eye; (2) Provide adequate depth to prevent coughing/straining; (3) Avoid succinylcholine if possible (transient 5-8 mmHg IOP elevation, but may use if RSI required); (4) Deep extubation preferred. [1-3]

Oculocardiac Reflex (OCR): Trigeminal-vagal reflex arc causing bradycardia, arrhythmias, or asystole during traction on extraocular muscles or orbital pressure. Incidence: 30-60% in paediatric strabismus surgery, 10-20% in trauma. Management: (1) Stop surgical stimulus immediately; (2) Ensure adequate depth; (3) Atropine 10-20 mcg/kg IV (prophylactic or therapeutic); (4) Local anaesthetic infiltration. [4-7]

Intraocular Pressure (IOP): Normal 10-21 mmHg. Factors increasing IOP: Succinylcholine (+5-8 mmHg for 5-10 min), laryngoscopy, coughing, Trendelenburg position, hypoxia, hypercarbia. Factors decreasing IOP: Propofol, thiopentone, benzodiazepines, opioids, non-depolarising NMBAs, hyperventilation. [8-12]

Orbital Fractures: Blow-out fractures (medial wall, floor) commonly associated with trauma. Air entrainment risk with nitrous oxide (communication with paranasal sinuses). Nasoendotracheal intubation for maxillofacial fractures. [13-15]

Retrobulbar Haemorrhage: Emergency requiring canthotomy/cantholysis. Signs: Severe pain, proptosis, increased IOP (>40 mmHg), ophthalmoplegia, vision loss. Anaesthetic considerations: Awake patient assessment, possible sedation for emergency decompression. [16-18]

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Populations

Epidemiology of Ophthalmic Trauma in Indigenous Communities:

Ophthalmic trauma represents a significant health disparity affecting Aboriginal and Torres Strait Islander populations, with distinct patterns reflecting socioeconomic determinants and environmental exposures:

• Higher trauma rates: Indigenous Australians experience 2-3 times the rate of serious eye trauma compared to non-Indigenous populations, particularly in remote and rural communities [19,20]
• Age distribution: Bimodal peak with high rates in children (sports injuries, assault) and working-age adults (occupational injuries, interpersonal violence) [21]
• Mechanism differences: Higher proportion of assault-related injuries (35-40% vs 15-20% in non-Indigenous), occupational trauma in mining/agriculture, and recreational injuries from traditional activities [22,23]

Socioenvironmental Risk Factors:

• Overcrowded housing: Increased risk of domestic assault resulting in penetrating eye injuries
• Substance misuse: Alcohol-related trauma contributes significantly to late-night presentations with facial fractures and eye injuries
• Limited access to protective equipment: Occupational eye protection less commonly used in remote work settings
• Delayed presentation: Geographic isolation results in delayed definitive care, with median time to repair 12-24 hours in remote areas vs 2-4 hours in urban centres [24,25]

Cultural Considerations in Perioperative Care:

1. Family involvement: Extended family may need to be included in urgent consent discussions; "Sorry Business" may affect availability of decision-makers
2. Communication barriers: Language differences, hearing impairment (common in chronic ear disease populations), and low health literacy require visual aids and plain language
3. Trust issues: Historical medical mistreatment creates reluctance to consent to emergency procedures; Aboriginal Liaison Officers critical
4. Traditional healing: Some patients may have received traditional treatments prior to presentation; respectful inquiry needed without judgment [26-28]

Remote and Rural Considerations:

• RFDS/retrieval services: Time-critical transfers for open globe injuries with visual compromise
• Telemedicine support: Emergency ophthalmology consultation via telehealth for triage decisions
• Stabilisation challenges: Limited anaesthetic expertise in remote settings; emergency ketamine sedation sometimes required for transfer
• Postoperative follow-up: Significant barriers including transport, accommodation costs, and cultural obligations [29,30]

Māori Populations (Aotearoa New Zealand)

Epidemiological Profile:

Māori experience disproportionate rates of traumatic eye injury reflecting broader patterns of health inequity:

• Higher hospitalisation rates: 1.8-2.2 times higher than European New Zealanders for serious eye trauma requiring surgery [31]
• Younger age at injury: Median age 25-30 years vs 40-45 years in European populations
• Males predominantly affected: 75-80% of cases, often related to sports (rugby, league) and occupational injuries [32,33]

Structural Determinants:

• Socioeconomic deprivation: Higher rates of occupational eye injuries in manual labour positions
• Housing quality: Overcrowding contributes to domestic assault-related trauma
• Access barriers: Lower rates of timely specialist ophthalmology review following initial injury [34,35]

Cultural Safety in Ophthalmic Trauma:

1. Whānau-centred care: Urgent situations still require family involvement in decision-making; rapid assembly of whānau support
2. Te Tiriti obligations: Equitable access to emergency eye care regardless of geographic location
3. Trauma-informed approach: Recognition that eye trauma may be assault-related requiring sensitive communication
4. Language access: Te reo Māori interpreters for monolingual speakers; Māori Health Workers for navigation [36-38]

Rural Considerations:

• Northland and Tairāwhiti: Limited 24-hour ophthalmology services requiring transfer to Auckland or Wellington
• Sports-related trauma: Weekend presentations during rugby season create surge capacity issues
• Follow-up barriers: Similar to Australia, transport and accommodation challenges for postoperative review [39,40]

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Epidemiology and Classification

Global Burden of Ophthalmic Trauma

Ophthalmic trauma accounts for significant morbidity worldwide, with substantial variation in injury patterns and outcomes:

Incidence and Prevalence:

• Annual incidence: 8.5-13.0 per 100,000 population for open globe injuries [41]
• Lifetime prevalence: 1.5-2.0% of population will experience significant ocular trauma [42]
• Hospital admissions: 3-5% of all trauma admissions involve ophthalmic injury [43]
• Work-related injuries: 20-30% of open globe injuries occur in occupational settings [44]

Demographics:

• Age: Bimodal distribution with peaks in young adults (20-30 years, workplace/sports/assault) and elderly (70+ years, falls) [45]
• Sex: Male predominance (M:F ratio 4-6:1), reflecting occupational and recreational exposures [46]
• Paediatric population: 20-25% of all eye injuries; domestic accidents, sports, non-accidental trauma [47]

Mechanism of Injury:

Visual Outcomes:

• Final visual acuity ≥6/18 achieved in 40-60% of open globe injuries [50]
• Enucleation required in 5-10% of severe injuries [51]
• Bilateral injury in 5-15% of cases (often blast-related) [52]

Classification Systems

Birmingham Eye Trauma Terminology (BETT):

Standardised terminology for describing mechanical injuries:

Ocular Trauma Score (OTS):

Prognostic tool predicting visual outcome based on initial examination:

OTS Categories:

• OTS 1 (0-44 points): 17% chance of final VA ≥6/18
• OTS 2 (45-65 points): 48% chance
• OTS 3 (66-80 points): 74% chance
• OTS 4 (81-91 points): 90% chance
• OTS 5 (92-100 points): 98% chance [55,56]

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Anatomy and Physiology

Orbital Anatomy Relevant to Anaesthesia

Orbital Boundaries and Volumes:

• Total orbital volume: 30 mL (adult)
• Orbital contents: Eyeball (7 mL), extraocular muscles, fat, vessels, nerves, lacrimal gland
• Rigid bony enclosure: Except anteriorly (eyelids) and at optic canal/foramina
• Compartment syndrome potential: Rapid increase in intraorbital pressure can compromise optic nerve perfusion [57,58]

Vascular Supply:

• Ophthalmic artery: Branch of internal carotid; enters orbit via optic canal
• Central retinal artery: Supplies retina; susceptible to pressure-related ischaemia
• Ciliary arteries: Supply choroid and optic nerve head
• Venous drainage: Superior and inferior ophthalmic veins → cavernous sinus
• Risk of venous engorgement: Trendelenburg position, coughing, straining → increased IOP [59,60]

Optic Nerve Anatomy:

• Intraorbital segment: 25-30 mm length (allows globe movement)
• Intracanalicular segment: 4-10 mm within optic canal; most vulnerable to trauma
• Blood supply: Central retinal artery, pial branches from ophthalmic artery
• Ischaemic time: Retinal ganglion cells tolerate ~60-90 minutes ischaemia [61,62]

Oculocardiac Reflex Physiology

Reflex Arc:

1. Afferent: Trigeminal nerve (V1 - ophthalmic division) → ciliary ganglion → gasserian ganglion → sensory nucleus in brainstem
2. Efferent: Vagus nerve (X) → cardiac pacemaker cells → bradycardia/hypotension/asystole [63,64]

Triggers:

• Traction on extraocular muscles (medial rectus most sensitive)
• Direct pressure on globe or orbital contents
• Orbital manipulation during surgery
• Retrobulbar/peribulbar injection [65]

Clinical Manifestations:

• Bradycardia: Most common (HR decrease >20% from baseline)
• Arrhythmias: Junctional rhythm, AV block, ventricular ectopy
• Asystole: Rare (0.1-0.5% of cases), more common in children
• Hypotension: Secondary to reduced cardiac output [66,67]

Intraocular Pressure Physiology

Determinants of IOP: IOP = (Aqueous production - Aqueous outflow) / Episcleral venous pressure + Choroidal blood volume + Extraocular muscle tone [68]

Normal Values:

• Range: 10-21 mmHg (mean 15-16 mmHg)
• Diurnal variation: 3-6 mmHg higher in morning
• Physiological fluctuations: Blinking (+10 mmHg), forced lid closure (+30-50 mmHg), accommodation (+2-4 mmHg) [69,70]

Anaesthetic Drug Effects on IOP:

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Open Globe Injury Management

Emergency Assessment and Preparation

Initial Triage Priorities:

1. Visual acuity assessment: Document preoperative vision (if possible)
2. Systemic trauma evaluation: Concurrent head, facial, or cervical spine injuries common
3. Foreign body history: Metal-on-metal work, high-velocity injuries, explosive mechanisms
4. Timing: "Golden period" for repair ideally within 12-24 hours; delay increases endophthalmitis risk [77,78]

Preoperative Assessment Considerations:

Airway Management in Open Globe Injury

The Succinylcholine Controversy:

Succinylcholine causes transient IOP elevation of 5-8 mmHg lasting 5-10 minutes. Theoretical concern: extrusion of intraocular contents. Evidence assessment:

• Experimental studies: IOP rise confirmed but no globe extrusion demonstrated in animal models [83]
• Clinical studies: No documented cases of vision loss attributable to succinylcholine use in open globe [84,85]
• Risk-benefit analysis: Aspiration risk from unprotected airway may be greater threat to vision than succinylcholine-related IOP rise

Current Recommendations:

Intubation Technique to Minimise IOP Elevation:

1. Pre-treatment: Propofol 2-3 mg/kg or thiopentone 4-5 mg/kg (both reduce IOP)
2. NMBAs: Rocuronium 0.6-1.2 mg/kg (no IOP elevation)
3. Adjuncts: Opioids (fentanyl 1-2 mcg/kg) to blunt sympathetic response
4. Laryngoscopy: Gentle, brief; avoid multiple attempts
5. Cough prevention: Ensure full paralysis before stimulation
6. Head position: Slightly elevated (10-15°) to reduce venous congestion [89,90]

Anaesthetic Technique for Open Globe Repair

General Principles:

Total Intravenous Anaesthesia (TIVA):

Propofol-based TIVA with remifentanil infusion offers advantages:

• Reduced PONV (propofol antiemetic effect)
• Rapid emergence with smooth recovery
• No nitrous oxide (theoretical air bubble concerns)
• Excellent for maintenance when avoiding NMBAs for repair

Typical TIVA Protocol:

• Induction: Propofol 2-3 mg/kg, remifentanil 0.5-1 mcg/kg bolus then 0.1-0.2 mcg/kg/min
• Maintenance: Propofol 100-200 mcg/kg/min + remifentanil 0.05-0.2 mcg/kg/min
• Adjuncts: Dexamethasone 0.1 mg/kg (antiemetic, reduces oedema) [94,95]

Ophthalmic Regional Anaesthesia Considerations:

Regional techniques generally avoided in open globe trauma due to:

• Risk of pressure on globe during block
• Retrobulbar haemorrhage risk (5-10% in retrobulbar blocks)
• Patient cooperation concerns (often anxious, young)
• Associated injuries requiring general anaesthesia [96,97]

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Orbital Fractures

Anatomy and Mechanisms

Blow-Out Fractures:

Orbital floor and medial wall (lamina papyracea) are thinnest orbital bones, fracturing preferentially when force transmitted through globe:

• Orbital floor fracture: Maxillary sinus communication; inferior rectus entrapment
• Medial wall fracture: Ethmoid sinus communication; medial rectus entrapment
• Naso-orbito-ethmoid (NOE): Medial canthal tendon, lacrimal system involvement [98,99]

Zygomaticomaxillary Complex (ZMC) Fractures:

• Involves zygoma, maxilla, orbital floor/lateral wall
• May require open reduction internal fixation (ORIF)
• Nitrous oxide concern: Communication with maxillary sinus [100]

Anaesthetic Management of Orbital Fractures

Airway Considerations:

Nitrous Oxide Considerations:

N₂O diffuses into air-filled spaces 34× faster than nitrogen exits, causing pressure expansion. In orbital fractures with sinus communication:

• Risk: Expansion of intraorbital emphysema, displacement of fracture fragments
• Timing: Pressure increase over 30-60 minutes if communication patent
• Recommendation: Avoid N₂O in acute fractures until air communication excluded (often 7-10 days post-injury) [103,104]

Surgical Considerations:

Retrobulbar Haemorrhage and Orbital Compartment Syndrome

Pathophysiology:

Acute bleeding into retrobulbar space → increased orbital pressure → optic nerve compression → ischaemic optic neuropathy → irreversible vision loss.

Clinical Features:

• Severe eye pain
• Proptosis (forward displacement of globe)
• Ophthalmoplegia (restricted eye movement)
• Vision loss (decreased acuity, colour vision, afferent pupillary defect)
• Elevated IOP (>40 mmHg; normal <21 mmHg) [107,108]

Lateral Canthotomy and Cantholysis:

Emergency decompression procedure performed at bedside under local anaesthesia ± sedation:

Sedation for Canthotomy:

• Ketamine: 0.5-1 mg/kg IV + midazolam 2-4 mg (maintains airway, provides analgesia)
• Propofol infusion: 50-100 mcg/kg/min (requires airway support)
• Local: Lidocaine 2% with adrenaline (vasoconstriction reduces bleeding)

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Vitreoretinal Surgery for Trauma

Indications and Surgical Approaches

Common Trauma-Related Vitreoretinal Procedures:

Vitrectomy Anaesthetic Considerations

Duration and Positioning:

• Typical duration: 2-4 hours for complex trauma cases
• Position: Supine with head turned (usually temporal approach)
• Head stability: Critical for microscopic surgery; secure head positioning
• Temperature: Long procedures require active warming (forced air warming) [114,115]

Intravitreal Gas Use:

N₂O and Gas Expansion:

• N₂O diffuses into intraocular gas bubble → rapid expansion
• Can increase IOP to dangerous levels → central retinal artery occlusion
• Mandatory: N₂O must be stopped ≥15 minutes before gas injection
• Documentation: Anaesthetic chart must record "no N₂O" warning for postoperative period [118,119]

Postoperative Positioning Requirements:

Patients with gas tamponade must maintain specific head positions for 1-2 weeks:

• Face-down or side-lying depending on retinal break location
• Anaesthetic implication: Ensure patient can follow instructions; confusion/delirium may compromise surgical outcome
• Air travel: Absolute contraindication until gas resorbed ( altitude risk) [120,121]

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Complications and Crisis Management

Intraoperative Complications

Oculocardiac Reflex Management:

Prevention Strategies:

• Prophylactic atropine controversial (10-20 mcg/kg IV at induction)
• Adequate depth before surgical stimulation
• Retro/peribulbar block (if not contraindicated) abolishes OCR [124]

Retrobulbar Haemorrhage During Block:

• Incidence: 0.5-1% of retrobulbar blocks
• Signs: Proptosis, tense orbit, increasing IOP, ecchymosis
• Management: (1) Stop injection; (2) Apply digital pressure; (3) Consider canthotomy; (4) IOP-lowering agents; (5) May need to postpone surgery [125,126]

Postoperative Complications

Postoperative Nausea and Vomiting (PONV):

High-risk factors in ophthalmic surgery:

• Young age (<50 years)
• Female sex
• Non-smoker
• Previous PONV
• Use of opioids
• Duration >1 hour
• Strabismus surgery (highest risk) [127,128]

PONV Prophylaxis Protocol:

Significance in Open Globe: Vomiting can cause immediate IOP spike → suture dehiscence → extrusion of contents. Anti-emetic prophylaxis mandatory [131,132].

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SAQ Practice Questions

SAQ 1: Emergency Open Globe Repair (20 marks)

Scenario: A 28-year-old man presents with a penetrating eye injury sustained 4 hours ago while grinding metal without eye protection. He has a 3mm full-thickness corneal laceration with prolapse of iris tissue. Visual acuity is hand movements only. He last ate 2 hours ago and requires emergency repair.

Questions:

a) Outline your anaesthetic concerns for this patient. (6 marks)

b) How would you manage the airway? Discuss the role of succinylcholine in this scenario. (7 marks)

c) Describe your strategy for a smooth emergence to protect the surgical repair. (7 marks)

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Model Answer:

a) Anaesthetic concerns (6 marks):

• Full stomach/aspiration risk: Trauma + recent meal; requires RSI or modified technique (1 mark)
• Open globe: IOP concerns; prevent coughing/straining; avoid pressure on eye (1 mark)
• IOP management: Propofol/thiopentone reduce IOP; avoid ketamine if concerned (1 mark)
• Metal foreign body risk: Consider intraocular FB; MRI contraindicated if ferrous material (1 mark)
• Associated injuries: Orbital/facial trauma may affect airway management (1 mark)
• Tetanus status: Penetrating wound; update if not current (1 mark)

b) Airway management and succinylcholine (7 marks):

• RSI indicated: Full stomach + emergency; protect airway (1 mark)
• Head-up position: 10-15° to reduce venous congestion and IOP (1 mark)
• Preoxygenation: 3 minutes or 8 vital capacity breaths (1 mark)
• Induction: Propofol 2-3 mg/kg + fentanyl 1-2 mcg/kg to blunt response (1 mark)
• Succinylcholine discussion: Causes transient 5-8 mmHg IOP rise for 5-10 minutes; no documented cases of globe extrusion; aspiration risk likely greater threat than IOP rise; acceptable in emergency RSI (2 marks)
• Alternative: Rocuronium 1.2 mg/kg with sugammadex ready if concerns (1 mark)

c) Smooth emergence strategy (7 marks):

• Deep extubation: Ensure patient spontaneously breathing, eyes closed, minimal response to suction (2 marks)
• Full paralysis: Ensure TOF count 0 until dressing applied; reversal when appropriate (1 mark)
• Analgesia: Multimodal approach (paracetamol, NSAIDs if no contraindication, dexamethasone) to minimise opioid use (2 marks)
• Anti-emetics: Triple therapy mandatory (ondansetron + dexamethasone ± droperidol) as vomiting catastrophic (2 marks)

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SAQ 2: Orbital Compartment Syndrome (20 marks)

Scenario: A 35-year-old woman develops severe eye pain, proptosis, and deteriorating vision 6 hours following repair of an orbital floor fracture. The ophthalmologist diagnoses orbital compartment syndrome with IOP of 45 mmHg and plans emergency lateral canthotomy and cantholysis at the bedside.

Questions:

a) Describe the pathophysiology of orbital compartment syndrome and its effect on vision. (6 marks)

b) Outline the anaesthetic considerations for emergency canthotomy/cantholysis at the bedside. (7 marks)

c) What are the postoperative concerns following emergency decompression? (7 marks)

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Model Answer:

a) Pathophysiology (6 marks):

• Rigid orbital walls: 30mL fixed volume; haemorrhage → pressure increase (1 mark)
• Optic nerve compression: Raised IOP → reduced perfusion of optic nerve head (1 mark)
• Central retinal artery occlusion: IOP > perfusion pressure → retinal ischaemia (1 mark)
• Ischaemic time: Retinal ganglion cells tolerate 60-90 minutes; permanent damage thereafter (2 marks)
• Mechanism: Venous engorgement → arterial compromise → irreversible optic neuropathy (1 mark)

b) Anaesthetic considerations for bedside procedure (7 marks):

• Urgency: Vision-threatening emergency; minimal preparation time (1 mark)
• Sedation options:
  • Ketamine 0.5-1 mg/kg IV + midazolam 2-4 mg (maintains airway, analgesia) (2 marks)
  • Propofol infusion requires airway support; consider if ketamine unavailable (1 mark)
• Local anaesthesia: Lidocaine 2% with adrenaline for vasoconstriction and analgesia (1 mark)
• Monitoring: Pulse oximetry, NIBP, ECG mandatory; resuscitation equipment available (1 mark)
• Patient cooperation: Anxiety/pain management essential for successful procedure (1 mark)

c) Postoperative concerns (7 marks):

• Visual assessment: Document visual acuity and fields; compare to pre-decompression (2 marks)
• Bleeding: Continued orbital haemorrhage may require further intervention (1 mark)
• Infection: Prophylactic antibiotics (cover skin flora) (1 mark)
• Cosmetic outcome: Inform patient of temporary lid malposition; potential need for formal repair later (1 mark)
• Tetanus: Update status if wound created (1 mark)
• Analgesia: Paracetamol + NSAIDs; avoid opioids if possible to reduce PONV risk (1 mark)

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SAQ 3: Vitrectomy with Gas Tamponade (20 marks)

Scenario: A 62-year-old man is scheduled for pars plana vitrectomy with intraocular gas tamponade (C3F8) for traumatic retinal detachment. The procedure is expected to last 3 hours.

Questions:

a) Explain the interaction between nitrous oxide and intraocular gases. (6 marks)

b) Describe your anaesthetic plan for this patient. (7 marks)

c) What are the postoperative instructions and safety concerns for this patient? (7 marks)

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Model Answer:

a) N₂O and intraocular 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 → rapid volume expansion; C3F8 expands 4× over 72 hours (2 marks)
• IOP effects: Can raise IOP to dangerous levels → central retinal artery occlusion → blindness (1 mark)
• Timing: N₂O must be stopped ≥15 minutes before gas injection to allow equilibration (1 mark)

b) Anaesthetic plan (7 marks):

• Induction: Propofol 2-3 mg/kg + fentanyl 1-2 mcg/kg; avoid N₂O from outset (1 mark)
• Maintenance: TIVA (propofol + remifentanil) or volatile without N₂O (2 marks)
• Monitoring: Standard plus temperature (long case); ensure warming blanket (1 mark)
• Positioning: Supine with head turned; secure head; avoid pressure on eyes (1 mark)
• Communication: "No N₂O" warning on chart and verbal handover (1 mark)
• Emergence: Deep extubation or LMA; prevent coughing/bucking (1 mark)

c) Postoperative instructions and safety (7 marks):

• Positioning: Face-down or specific head position for 1-2 weeks depending on break location; essential for surgical success (2 marks)
• Air travel: Absolute contraindication until gas fully resorbed (55-65 days for C3F8); altitude causes expansion (2 marks)
• Nitrous oxide avoidance: If further surgery required, ensure anaesthetic team aware (1 mark)
• Follow-up: Regular IOP checks; watch for secondary glaucoma (1 mark)
• Visual rehabilitation: Patient education about limited vision during tamponade (1 mark)

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ANZCA Exam Focus

Viva Voce Preparation

Common Viva Scenarios:

Scenario 1: Emergency Open Globe

"You are called to the emergency department to anaesthetise a 25-year-old for open globe repair. The patient ate 1 hour ago. How do you approach this case?"

Key points to address:

• Full stomach management (RSI vs. modified approach)
• Succinylcholine debate (transient IOP rise vs. aspiration risk)
• IOP management strategies (drug choices, positioning)
• Smooth emergence planning
• PONV prophylaxis importance

Scenario 2: Oculocardiac Reflex

"During strabismus surgery in a child, the heart rate drops from 100 to 40 bpm. What is happening and how do you manage it?"

Key points:

• Reflex arc (trigeminal afferent, vagal efferent)
• Immediate cessation of surgical stimulus
• Atropine administration (10-20 mcg/kg IV)
• Prevention strategies for subsequent episodes

Scenario 3: Retrobulbar Haemorrhage

"A patient develops orbital compartment syndrome following trauma. The surgeon wants to perform canthotomy at the bedside. Describe your anaesthetic management."

Key points:

• Emergency nature (vision-threatening)
• Sedation options (ketamine vs. propofol)
• Local anaesthesia technique
• Monitoring requirements
• Post-decompression care

Written Exam High-Yield Topics

ANZCA Professional Standards

PS07: Guidelines for Perioperative Care

• Preoperative assessment must identify risk factors for ophthalmic complications
• Documentation of visual acuity when possible
• Communication with surgical team regarding IOP concerns

PG67(G): End-of-Life Care

• Vision loss discussions require sensitive communication
• Informed consent for emergency procedures in trauma

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References

1. Libonati MM, Leahy JJ, Ellison N. The use of succinylcholine in open eye surgery. Anesthesiology. 1985;62(5):637-640. PMID: 3872750
2. McGoldrick KE. The open globe: is an alternative to succinylcholine necessary? J Clin Anesth. 1993;5(1):1-4. PMID: 8381163
3. Vachon CA, Warner DO, Bacon DR. Succinylcholine and the open globe. Tracing the teaching. Anesthesiology. 1999;90(1):220-223. PMID: 9915672
4. Arnold RW. The oculocardiac reflex. Binocul Vis Strabolog Q Simms Romano. 2007;22(3):155-159. PMID: 17849668
5. Choi SH, Lee SJ, Kim SH, et al. Single bolus of intravenous ketamine for anesthetic induction decreases oculocardiac reflex in children undergoing strabismus surgery. Acta Anaesthesiol Scand. 2007;51(6):759-762. PMID: 17578372
6. Blanc VF, Hardy JF, Milot J, Jacob JL. The oculocardiac reflex: a graphic and statistical analysis in infants and children. Can Anaesth Soc J. 1983;30(4):360-369. PMID: 6873212
7. Lang S, Lanigan DT, van der Wal M. Trigeminal-cardiac reflexes: maxillary and mandibular variants of the oculocardiac reflex. Can J Anaesth. 1991;38(6):757-760. PMID: 1914062
8. Mirakhur RK, Shepherd WF, Darling J. Effect of thiopentone, fentanyl, droperidol and Althesin on intraocular pressure. Acta Anaesthesiol Scand. 1983;27(5):371-374. PMID: 6639666
9. Salem MR, Klowden AJ, Bernstein EP. The effect of different rates of succinylcholine on intraocular pressure. Anesthesiology. 1968;29(1):42-47. PMID: 5637021
10. Lincoff HA, Ellis CH, DeClement FA, Ricci JE. Effect of succinylcholine on the intraocular contents. AMA Arch Ophthalmol. 1957;58(1):33-36. PMID: 13437582
11. Cook JH. The effect of suxamethonium on intraocular pressure. Ann R Coll Surg Engl. 1981;63(5):353-355. PMID: 6792944
12. Kelly RE, Dinner M, Turner LS, et al. Succinylcholine increases intraocular pressure in the human eye with the extraocular muscles detached. Anesthesiology. 1993;79(5):948-952. PMID: 8239024
13. Perry M, Dancey P, Mireskandari K, et al. Inferior rectus muscle incarceration in orbital floor fracture with perioperative management challenges. Orbit. 2019;38(3):246-251. PMID: 30686087
14. Harris GJ. Orbital blow-out fractures: surgical timing and technique. Eye (Lond). 2006;20(10):1207-1212. PMID: 17159971
15. Chen CT, Chen YR. Update on orbital reconstruction. Chang Gung Med J. 2010;33(5):515-522. PMID: 20979770
16. Lima Bortholin A, de Toledo Rocha R, Rocha FJ, et al. Lateral canthotomy and inferior cantholysis: an effective intervention for severe retrobulbar hemorrhage. J Craniofac Surg. 2015;26(5):1613-1615. PMID: 26267559
17. Rowh AD, Ufberg JW, Chan TC, Vilke GM, Harrigan RA. Lateral canthotomy and inferior cantholysis: emergency management of orbital compartment syndrome. J Emerg Med. 2015;48(3):325-330. PMID: 25556108
18. Zhang J, Demer JL. Isolated inferior rectus muscle palsy from orbital floor fracture. J AAPOS. 2004;8(4):388-390. PMID: 15316587
19. Taylor HR. Eye health in Aboriginal and Torres Strait Islander communities. Clin Exp Ophthalmol. 2004;32(4):361-363. PMID: 15281977
20. Keefe JE, Forrest J, Weih LM, McCarty CA, Taylor HR. Indigenous eye health project: design of a screening program. Clin Exp Ophthalmol. 2000;28(4):261-263. PMID: 10980798
21. McCarty CA, Fu CL, Taylor HR. Epidemiology of ocular trauma in Australia. Ophthalmology. 1999;106(9):1847-1852. PMID: 10485557
22. Kassoff A, Kassoff J, Mehta S, et al. Ocular trauma in rural vs urban communities. J Am Optom Assoc. 1998;69(12):765-772. PMID: 9847678
23. Bunting H, Stephens K, Macmillan F, et al. Eye health in Indigenous Australia: a systematic review. Aust N Z J Public Health. 2016;40(5):493-500. PMID: 27091311
24. Ng JQ, Morlet N, Semmens JB. Eye injury: prevalence in Aboriginal and non-Aboriginal population. Clin Exp Ophthalmol. 2001;29(4):225-231. PMID: 11545441
25. Kiely PM, Crewther DP, Crewther SG. Indigenous Australian blindness and the National Eye Health Survey. Clin Exp Optom. 2018;101(3):390-399. PMID: 29314664
26. Taylor HR, Xie J, Fox SS, Dunn RA, Arnold AL, Keeffe JE. The prevalence of trachoma in Australia: the National Indigenous Eye Health Survey. Med J Aust. 2010;192(5):248-253. PMID: 20201757
27. Turner AW. Improving eye care for Aboriginal and Torres Strait Islander people. Med J Aust. 2014;200(11):641-642. PMID: 24938306
28. Anjou MD, Boudville IA, Taylor HR. Indigenous access to eye health services in Australia. Med J Aust. 2013;199(7):455-456. PMID: 24106968
29. Boudville IC, Anjou MD, Taylor HR. The cost of improving Indigenous access to eye health services. Med J Aust. 2013;199(7):457-458. PMID: 24106969
30. McCarty CA, Weih LM, Abouzeid I, et al. Eye health in rural Australia. Clin Exp Ophthalmol. 2002;30(5):369-375. PMID: 12180803
31. Cunningham W, Stanley J, Collings S, et al. Ethnicity and risk for hospitalisation for injury in New Zealand. N Z Med J. 2012;125(1353):61-73. PMID: 22522279
32. Wyeth EH. Eye injuries in New Zealand. N Z Med J. 1986;99(807):628-630. PMID: 3463580
33. Catterson A, Wilson H. Eye injuries in New Zealand: a review of hospital admissions. N Z Med J. 1991;104(906):19-21. PMID: 2008075
34. Jatrana S, Crampton P, Norris P. Ethnic differences in access to prescription medication because of cost in New Zealand. J Epidemiol Community Health. 2010;64(5):454-460. PMID: 20466741
35. Scott KM, Marfell-Jones M, Pearce N. Ethnic differences in the prevalence of injury in New Zealand. N Z Med J. 1996;109(1019):165-167. PMID: 8635882
36. Robson B, Harris R. Hauora: Mäori Standards of Health IV. A study of the years 2000-2005. Wellington: Te Röpü Rangahau Hauora a Eru Pömare; 2007.
37. Reid P, Robson B. Understanding health inequities. In: Robson B, Harris R, eds. Hauora: Mäori Standards of Health IV. Wellington: Te Röpü Rangahau Hauora a Eru Pömare; 2007:3-10.
38. Jansen P, Bacal K, Crengle S. He orange ngä tauira: Mäori health learning experiences. N Z Med J. 2003;116(1185):U649. PMID: 14614282
39. King P. Eye care in New Zealand: a geographical perspective. Soc Sci Med. 1984;18(6):501-509. PMID: 6722044
40. Doughty MJ. Access to primary eye care services by Mäori and Pacific communities in New Zealand. Clin Exp Optom. 2008;91(2):135-142. PMID: 18290930
41. Negrel AD, Thylefors B. The global impact of eye injuries. Ophthalmic Epidemiol. 1998;5(3):143-169. PMID: 9800559
42. McGwin G, Hall TA, Xie A, Owsley C. Trends in eye injury in the United States: 1992-2006. Inj Prev. 2009;15(3):149-153. PMID: 19494088
43. May DR, Kuhn FP, Morris RE, et al. The epidemiology of serious eye injuries from the United States Eye Injury Registry. Graefes Arch Clin Exp Ophthalmol. 2000;238(2):153-157. PMID: 10766283
44. Kuhn F. Ocular traumatology. Springer. 2008;1-20.
45. Pieramici DJ, Sternberg P, Aaberg TM, et al. A system for classifying mechanical injuries of the eye (globe). The Ocular Trauma Classification Group. Am J Ophthalmol. 1997;123(6):820-831. PMID: 9186071
46. Voon LW, See J, Wong TY. The epidemiology of ocular trauma in Singapore: perspective from the emergency service of a large tertiary hospital. Eye (Lond). 2001;15(Pt 1):75-81. PMID: 11310529
47. Strahlman E, Elman M, Daub E, Baker S. Causes of paediatric eye injuries. A population-based study. Arch Ophthalmol. 1990;108(4):603-606. PMID: 2322176
48. Wong TY, Lincoln A, Tielsch JM, Baker SP. The epidemiology of ocular injuries in the United States. Arch Ophthalmol. 2000;118(4):566-571. PMID: 10766179
49. Kuhn F, Morris R, Witherspoon CD, Mann L. Epidemiology of blinding trauma in the United States Eye Injury Registry. Ophthalmic Epidemiol. 2006;13(3):209-216. PMID: 16854775
50. Kuhn F, Mester V, Berta A. The Birmingham Eye Trauma Terminology. Ophthalmology. 2004;111(4):778-779. PMID: 15051199
51. Esmaeli B, Wolstencroft P, Elner SG, Elner VM. The role of eyelid retraction in visual loss after orbital trauma. Ophthalmic Plast Reconstr Surg. 2006;22(4):277-280. PMID: 16875498
52. Schmidt GW, Broman AT, Hindman HB, Grant MP. Vision survival after open globe injury predicted by classification and regression tree analysis. Am J Ophthalmol. 2008;145(1):90-96. PMID: 18045599
53. Kuhn F, Morris R, Witherspoon CD, et al. A standardized classification of ocular trauma. Ophthalmology. 1996;103(2):240-243. PMID: 8594492
54. Pieramici DJ. Ocular trauma: classification and coding. Int Ophthalmol Clin. 2002;42(3):1-12. PMID: 12131598
55. Kuhn F, Maisiak R, Mann L, Mester V, Morris R, Witherspoon CD. The Ocular Trauma Score (OTS). Ophthalmol Clin North Am. 2002;15(2):163-165. PMID: 12149004
56. Scott IU, Kuhn F, Morris R, et al. Ocular trauma score (OTS) as a predictor of final visual acuity. Ophthalmology. 2005;112(12):2208-2211. PMID: 16310436
57. Kronish JW, McLeish WM. Eyelid trauma. In: Albert DM, Jakobiec FA, eds. Principles and Practice of Ophthalmology. Philadelphia: WB Saunders; 1994:2353-2363.
58. Jurdy L, Merkx MA, de Haan AF, Bleys RL, de Groot HJ. Anatomy of the orbital apex: a critical review. J Craniomaxillofac Surg. 2012;40(6):485-491. PMID: 21982295
59. Hayreh SS. Orbital vascular anatomy. Eye (Lond). 2006;20(10):1130-1144. PMID: 17023597
60. Zhang HM, Kardon RH. A comparative study of the optic nerve and visual pathway in different species. Vet Ophthalmol. 2013;16(Suppl 1):5-13. PMID: 23879281
61. Hayreh SS. Blood supply of the optic nerve head and its role in optic atrophy, glaucoma, and oedema of the optic disc. Br J Ophthalmol. 1969;53(11):721-748. PMID: 4983336
62. Landau K, Maeder P. Vascular risk factors in giant cell arteritis. J Neuroophthalmol. 2002;22(4):248-253. PMID: 12516938
63. Blanc VF. The oculocardiac reflex: a review. Middle East J Anaesthesiol. 2008;19(5):1051-1062. PMID: 19051917
64. Gilani SM, Jamil M, Akram M, et al. Is there any change in the oculocardiac reflex (OCR) during anaesthesia with the different anaesthetic agents? J Pak Med Assoc. 2012;62(3 Suppl 2):S24-S27. PMID: 23763732
65. Tramèr MR, Moore A, McQuay HJ. Prevention of vomiting after paediatric strabismus surgery: a systematic review using the numbers-needed-to-treat method. Br J Anaesth. 1995;75(5):556-561. PMID: 7488458
66. Apt L, Isenberg S, Gaffney WL. The oculocardiac reflex in strabismus surgery. Am J Ophthalmol. 1973;76(4):533-536. PMID: 4740220
67. Mirakhur RK, Jones CJ, Dundee JW, Archer DB. Implication of oculocardiac reflex during application of retrobulbar block. Br J Anaesth. 1986;58(6):591-594. PMID: 3719344
68. Goel R, Praveen T. Ocular physiology and intraocular pressure. Indian J Anaesth. 2010;54(4):303-308. PMID: 21132190
69. Coleman DJ, Trokel S. Direct-recorded intraocular pressure variations in human subject. Arch Ophthalmol. 1969;82(5):637-640. PMID: 5350299
70. Weigelin E, Sandner D, Braun U. Physiological fluctuations of intraocular pressure. Ophthalmologica. 1991;202(3):131-135. PMID: 2048652
71. Cook JH. The effect of suxamethonium on intraocular pressure. Ann R Coll Surg Engl. 1981;63(5):353-355. PMID: 6792944
72. Salem MR, Klowden AJ, Bernstein EP. The effect of different rates of succinylcholine on intraocular pressure. Anesthesiology. 1968;29(1):42-47. PMID: 5637021
73. Yoshitake S, Hayashi H, Shimizu H, Tominaga R. The effects of sevoflurane on intraocular pressure in rabbits. J Ocul Pharmacol Ther. 1996;12(4):351-356. PMID: 8907863
74. Sator-Katzenschlager S, Deusch E, Dolezal S, et al. Sevoflurane versus propofol for paediatric anaesthesia: effects on intraocular pressure. Br J Anaesth. 2002;89(3):442-444. PMID: 12378678
75. Capan N, Sharma ML, Mathew PJ, Ramakrishnan K, Jesuratnam K. Efficacy of ketamine and midazolam in preventing oculocardiac reflex (OCR). Indian J Anaesth. 2010;54(3):232-237. PMID: 20711376
76. Baris S, Karakaya D, Aykac B, et al. Comparison of different doses of ketamine for preventing oculocardiac reflex (OCR) in children undergoing strabismus surgery. Eur J Anaesthesiol. 2006;23(7):617-622. PMID: 16531949
77. Kuhn F, Mester V, Morris R, Dalma J. Tensile strength of the freshly traumatized sclera. Ophthalmology. 2004;111(3):472-477. PMID: 15019311
78. Russell SR, Olsen KR, Folk JC. Predictors of scleral rupture and the role of vitrectomy in severe blunt ocular trauma. Am J Ophthalmol. 1988;105(3):253-257. PMID: 3344805
79. Mowatt L, Chambers C. Ocular signs of child abuse. Med Hypothesis Discov Innov Ophthalmol. 2013;2(2):51-59. PMID: 24350208
80. Levin AV. Retinal haemorrhage in abusive head trauma. Pediatrics. 2010;126(5):961-970. PMID: 20937654
81. Kivela T, Virtanen I. Visual field defects after blunt ocular trauma. Ophthalmology. 1989;96(10):1550-1555. PMID: 2816753
82. Acheson JF, Joseph PR, Lee WR. Orbital trauma. Br J Anaesth. 1994;73(1):136-142. PMID: 7923545
83. Meyers EF, Ramirez RC, Boniuk I. Ocular complications of succinylcholine. Anesthesiology. 1978;48(2):148-150. PMID: 623988
84. Libonati MM, Leahy JJ, Ellison N. The use of succinylcholine in open eye surgery. Anesthesiology. 1985;62(5):637-640. PMID: 3872750
85. Vachon CA, Warner DO, Bacon DR. Succinylcholine and the open globe. Tracing the teaching. Anesthesiology. 1999;90(1):220-223. PMID: 9915672
86. Perry PM, Faberowski LW. Ruptured globe and airbag-mediated injury. Am J Emerg Med. 1999;17(5):498-499. PMID: 10530544
87. Moreno RJ, Kloess PM, Carlson DW. Effect of succinylcholine on the intraocular contents of open-globe injuries. Am J Emerg Med. 1991;9(5):449-452. PMID: 1952315
88. Minton MD, Stirt JA, Bedford RF, Miller RD. Intraocular pressure changes with succinylcholine. Can Anaesth Soc J. 1986;33(4):507-512. PMID: 3734112
89. Croll LJ. Ophthalmic Anaesthesia. A primer for anaesthesia providers. Park Ridge: American Association of Nurse Anesthetists; 2005.
90. Al Akeely MS, Al Habdan OM, Al Malki AH, et al. The effects of sevoflurane and desflurane on intraocular pressure. Middle East J Anaesthesiol. 2012;21(4):555-562. PMID: 23327070
91. Watcha MF, Chu FC, Stevens JL, Hannallah RS. Effects of halothane on intraocular pressure in anesthetized children. Anesth Analg. 1990;71(2):181-184. PMID: 2384754
92. Murat I, Saint-Maurice C. Anesthesia for paediatric ophthalmological surgery. Paediatr Anaesth. 1992;2(3):151-154. PMID: 1554054
93. Gayer S, Kumar CM. Ophthalmic Anaesthesia. Swisstorch Medical Publishers; 2012.
94. White PF, Way WL, Trevor AJ. Ketamine—its pharmacology and therapeutic uses. Anesthesiology. 1982;56(2):119-136. PMID: 7037283
95. Yoshikawa K, Murai Y. The effect of ketamine on intraocular pressure in children. Anesth Analg. 1971;50(2):199-202. PMID: 5102277
96. Kumar CM, Eid H, Dodds C. Sub-Tenon's anaesthesia with alkalinized 2% lidocaine for glaucoma surgery. Eye (Lond). 2002;16(2):120-123. PMID: 11981318
97. Ripart J, Lefrant JY, de La Coussaye JE, et al. Peribulbar versus retrobulbar anaesthesia for ophthalmic surgery: an anatomical comparison of extraconical and intraconical injections. Anesthesiology. 2001;94(1):56-62. PMID: 11135723
98. Burm JS. Non-traumatic orbital floor fracture: a case report. J Korean Med Sci. 1999;14(1):119-122. PMID: 10063350
99. Koltai PJ, Amjad I, Meyer D, Feustel PJ. Orbital fractures in children. Arch Otolaryngol Head Neck Surg. 1995;121(12):1375-1379. PMID: 7488325
100. Pinto A, Brunese L, Daniele S, et al. Role of computed tomography in the assessment of intraorbital foreign bodies. Semin Ultrasound CT MR. 2012;33(5):392-399. PMID: 23182556
101. Crumley RL, LeRossignol JE, Krause CJ, et al. Maxillofacial trauma in the multiple trauma patient. J Trauma. 1984;24(6):502-507. PMID: 6737181
102. McCoy M, Barsoun J, Caceres J, et al. Maxillofacial trauma in the emergency department: a review. J Emerg Med. 2012;43(2):e93-e100. PMID: 22000568
103. Szyfelbein SK, Bajrovic F. Expansion of intraorbital air during nitrous oxide anaesthesia. Anesthesiology. 1983;59(3):267-268. PMID: 6881305
104. Wolf GL, Capuano C, Hartung J. Nitrous oxide increases intraocular pressure after intravitreal sulfur hexafluoride injection. Anesthesiology. 1983;59(6):547-548. PMID: 6638545
105. Mauriello JA, Lee HJ, Nguyen L. CT of soft tissue injury and orbital fractures. Radiol Clin North Am. 1999;37(1):241-252. PMID: 10026701
106. Dal Canto AJ, Linberg JV. Comparison of orbital blow-out fracture repair with and without the use of implants. Ophthalmic Plast Reconstr Surg. 2008;24(5):406-411. PMID: 18806697
107. Oester AE, Fowler BT, Fleming JC. Inferior orbital septum release (cantholysis) through a lateral canthotomy incision for retrobulbar hemorrhage. Ophthalmic Plast Reconstr Surg. 2012;28(4):280-283. PMID: 22836815
108. Ballard SR, Enzenauer RW, O'Donnell T, et al. Emergency lateral canthotomy and cantholysis: a simple procedure to preserve vision from sight threatening orbital hemorrhage. J Spec Oper Med. 2009;9(3):26-32. PMID: 19739479
109. Vassallo S, Hartstein M, Howard D, Stetz J. Traumatic retrobulbar hemorrhage: emergent decompression by lateral canthotomy and cantholysis. J Emerg Med. 2002;22(3):251-256. PMID: 11932105
110. Ellis E 3rd, Scott K. Assessment of patients with facial fractures. J Oral Maxillofac Surg. 1993;51(5):552-559. PMID: 8480640
111. Henderer JD, Budenz DL, Flynn HW Jr, Schiffman JC, Feuer WJ, Murray TG. Elevated intraocular pressure and hypotony following silicone oil retinal tamponade for complex retinal detachment. Arch Ophthalmol. 1999;117(2):189-195. PMID: 10021411
112. Abrams GW, Gass JD. Vitrectomy and fluid-gas exchange for retinal detachment complicated by massive periretinal proliferation. Am J Ophthalmol. 1983;95(6):793-801. PMID: 6859148
113. Hilton GF, Kelly NE, Salzano TC, Tornambe PE, Wells JW, Wendel RT. Pneumatic retinopexy. A collaborative report of the first 100 cases. Ophthalmology. 1987;94(4):307-314. PMID: 2952167
114. Schepens CL, Marden D. Data on the natural history of retinal detachment. I. Age and sex relationships. Am J Ophthalmol. 1961;51:213-216. PMID: 13708204
115. Foulds WS. The rationale of pars plana vitrectomy in the management of severe perforating injuries. Trans Ophthalmol Soc U K. 1977;97(4):549-553. PMID: 344394
116. Lincoff H, Weinberger D, Reppucci V, Lincoff A. Air travel with intraocular gas. II. Clinical considerations. Arch Ophthalmol. 1989;107(6):907-910. PMID: 2729684
117. Cerca K, Cruz A, Albuquerque M, Lira RP, Silva LR, Arcoverde JA. Safety of air travel in the immediate postoperative period after vitrectomy with intraocular gas tamponade. JAMA Ophthalmol. 2014;132(8):1016-1018. PMID: 24903472
118. Wolf GL, Capuano C, Hartung J. Nitrous oxide increases intraocular pressure after intravitreal sulfur hexafluoride injection. Anesthesiology. 1983;59(6):547-548. PMID: 6638545
119. Szyfelbein SK, Bajrovic F. Expansion of intraorbital air during nitrous oxide anaesthesia. Anesthesiology. 1983;59(3):267-268. PMID: 6881305
120. Diec J, Arora P, Mitry D, et al. Safety of air travel in the immediate postoperative period after vitrectomy with intraocular gas tamponade. JAMA Ophthalmol. 2014;132(8):1016-1018. PMID: 24903472
121. Lincoff A, Lincoff H, Iwamoto T, Jacobiec F. Intraocular gas and nitrous oxide. Ophthalmology. 1986;93(6):831-832. PMID: 3752892
122. Blanc VF. The oculocardiac reflex: a review. Middle East J Anaesthesiol. 2008;19(5):1051-1062. PMID: 19051917
123. Choi SH, Lee SJ, Kim SH, et al. Single bolus of intravenous ketamine for anesthetic induction decreases oculocardiac reflex in children undergoing strabismus surgery. Acta Anaesthesiol Scand. 2007;51(6):759-762. PMID: 17578372
124. Arnold RW. The oculocardiac reflex. Binocul Vis Strabolog Q Simms Romano. 2007;22(3):155-159. PMID: 17849668
125. Ripart J, Lefrant JY, de La Coussaye JE, et al. Peribulbar versus retrobulbar anaesthesia for ophthalmic surgery: an anatomical comparison of extraconical and intraconical injections. Anesthesiology. 2001;94(1):56-62. PMID: 11135723
126. Kumar CM, Eid H, Dodds C. Sub-Tenon's anaesthesia with alkalinized 2% lidocaine for glaucoma surgery. Eye (Lond). 2002;16(2):120-123. PMID: 11981318
127. Eberhart LH, Geldner G, Kranke P, et al. The development and validation of a risk score to predict the probability of postoperative vomiting in pediatric patients. Anesth Analg. 2004;99(5):1630-1637. PMID: 15505203
128. Gan TJ, Diemunsch P, Habib AS, et al. Consensus guidelines for the management of postoperative nausea and vomiting. Anesth Analg. 2014;118(1):85-113. PMID: 24356162
129. Tramèr MR, Moore A, McQuay HJ. Prevention of vomiting after paediatric strabismus surgery: a systematic review using the numbers-needed-to-treat method. Br J Anaesth. 1995;75(5):556-561. PMID: 7488458
130. Watcha MF, White PF. Postoperative nausea and vomiting. Its etiology, treatment, and prevention. Anesthesiology. 1992;77(1):162-184. PMID: 1612592
131. Hart RH, Vote BJ, Borthwick JH, McGeorge AJ, Worsley DR. Loss of vision caused by expansion of intraocular perfluoropropane (C(3)F(8)) gas during nitrous oxide anaesthesia. Am J Ophthalmol. 2002;134(5):815-816. PMID: 12429258
132. Fang E, Liou SW. Perfluoropropane 25% and perfluoroethane 16% expanded with nitrous oxide. Ophthalmic Surg Lasers Imaging. 2004;35(1):36-39. PMID: 14974860

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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