Anaesthesia for Middle Ear Surgery

Quick Answer

Middle ear surgery encompasses tympanoplasty, mastoidectomy, stapedectomy, and cholesteatoma surgery. Key anaesthetic considerations include:

• Facial Nerve Monitoring: Electromyography (EMG) monitoring of the facial nerve is standard in mastoidectomy and cholesteatoma surgery. Requires avoidance of long-acting neuromuscular blocking agents (NMBAs); maintain TOF count ≥2 or use TIVA without NMBAs [1,2]

• Nitrous Oxide Controversy: N₂O diffuses into closed air spaces (middle ear) causing pressure changes. Concerns regarding graft displacement in tympanoplasty and postoperative nausea and vomiting (PONV). Modern evidence suggests safe with appropriate ventilation, but many avoid during graft placement [3,4]

• PONV Prevention: Ear surgery has high PONV incidence (60-80% without prophylaxis). Multimodal approach essential: dexamethasone + 5-HT₃ antagonist ± droperidol. Avoid nitrous oxide and minimise opioids [5,6]

• Patient Positioning: Head-up or supine with head rotation. Risk of venous air embolism (VAE) in mastoid surgery (rare, <1%). Ensure adequate venous drainage; Doppler monitoring if high-risk [7,8]

• Local Anaesthesia Infiltration: Many surgeons infiltrate the ear canal and temporal region with adrenaline-containing local anaesthetic. Risk of hypertension and tachycardia; ensure adequate anaesthetic depth [9,10]

• Chronic Suppurative Otitis Media (CSOM): High prevalence in Indigenous Australian and Māori children; may indicate repeat surgeries, adhesive disease, and challenging airways from chronic inflammation [11,12]

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Indigenous Health Considerations

Aboriginal and Torres Strait Islander Populations

Chronic Suppurative Otitis Media (CSOM) represents one of the most significant health disparities affecting Aboriginal and Torres Strait Islander children. The burden of disease is catastrophic:

• Prevalence in remote communities: 12-30% of children aged 0-4 years, compared to <1% in non-Indigenous urban populations [13,14]
• Hearing loss: Conductive hearing loss affects up to 40% of Indigenous children, profoundly impacting speech, language, and educational development [15,16]
• Age at presentation: Much younger than non-Indigenous children; often requires multiple surgical interventions including tympanostomy tubes, tympanoplasty, and mastoidectomy by school age [17]

Pathophysiology in Indigenous populations: The high CSOM rates relate to multifactorial determinants including overcrowded housing, poor sanitation, malnutrition, limited access to clean water, and delayed access to primary care [18,19]. The bacteria differ from urban populations:

• Higher rates of Pseudomonas aeruginosa and polymicrobial infections
• Increased antibiotic resistance due to recurrent treatment courses
• Higher incidence of biofilm formation requiring more aggressive surgical management [20,21]

Perioperative considerations for Indigenous patients:

1. Repeated surgeries: Many children require 3-5 ear surgeries by age 10, increasing cumulative anaesthetic exposure risks
2. Challenging anatomy: Chronic inflammation creates adhesive disease, sclerotic mastoid, and altered surgical anatomy
3. Nutritional status: Iron deficiency anaemia and poor growth common; requires preoperative optimisation
4. Communication barriers: Hearing impairment complicates preoperative assessment; may need visual communication aids
5. Geographic challenges: Fly-in fly-out (FIFO) surgical services create:
   • Limited preoperative optimisation time
   • Postoperative follow-up difficulties (recurrence monitoring, tube function)
   • Limited audiology access for hearing outcomes assessment [22,23,24]

Cultural safety considerations:

• Family-centred care with extended family involvement in consent
• Aboriginal Health Workers (AHWs) for communication support
• Recognition of impact on education and employment outcomes
• Telehealth follow-up partnerships with local Aboriginal Community Controlled Health Services (ACCHSs)
• "Sorry Business" may affect surgical timing and family availability [25,26]

Māori Populations (Aotearoa New Zealand)

Māori children experience similarly elevated rates of otitis media and related surgical interventions:

• Tympanostomy tube insertion rates 2× higher than European New Zealanders [27]
• Earlier age at first surgery and more frequent re-operations [28]
• Hearing loss impact: Disproportionate effect on educational attainment and te reo Māori language development [29]

Structural determinants:

• Overcrowding and housing quality issues (29% of Māori live in crowded households vs. 8% non-Māori)
• Higher smoking rates in households exposing children to second-hand smoke
• Geographic barriers to specialist care, particularly for rural iwi [30,31]

Te Tiriti o Waitangi obligations in ENT anaesthesia:

1. Active whānau involvement: Parents and extended family in perioperative decision-making
2. Māori Health Workers: Navigation support for hospital processes
3. Cultural considerations for hearing: Recognition that hearing impairment affects Māori language (te reo) acquisition and cultural identity development
4. Rheumatic fever connection: Streptococcal carriage in chronic otitis media may contribute to rheumatic fever risk, which is 3-4× higher in Māori children
5. Data sovereignty: Ensuring hearing outcomes data contributes to Māori-led health improvement initiatives [32,33]

Rural and remote considerations:

• Tairāwhiti, Northland, and Midland regions have limited ENT specialist access
• RFDS or local retrieval services for postoperative complications
• Partnership with local Māori health providers for follow-up care
• Community health workers monitoring for surgical site complications [34,35]

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Epidemiology and Clinical Overview

Surgical Indications

Tympanoplasty (myringoplasty):

• Perforated tympanic membrane with conductive hearing loss
• Chronic otitis media with or without cholesteatoma
• Traumatic perforation unhealed at 3-6 months
• Previous tympanostomy tube site non-healing

Mastoidectomy:

• Cholesteatoma (acquired or congenital)
• Chronic mastoiditis unresponsive to antibiotics
• Coalescent mastoiditis with intracranial/orbital complications
• Mastoid abscess
• Facial nerve decompression

Stapedectomy/stapedotomy:

• Otosclerosis with conductive hearing loss
• Air-bone gap >20-30 dB
• Progressive hearing impairment

Ossiculoplasty:

• Discontinuity or fixation of ossicular chain
• Traumatic ossicular disruption
• Chronic otitis media with ossicular erosion [36,37,38]

Surgical Techniques and Variations

Operative duration:

• Myringoplasty: 30-60 minutes
• Mastoidectomy: 1.5-3 hours
• Stapedectomy: 45-90 minutes
• Cochlear implantation: 2-4 hours [41,42]

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Anatomy and Physiology Relevant to Anaesthesia

Temporal Bone Anatomy

The temporal bone contains the external auditory canal, middle ear, inner ear, and mastoid air cells. Key structures:

• External auditory canal: Outer 1/3 cartilaginous, inner 2/3 bony; innervated by auriculotemporal nerve (V₃), vagus (Arnold's nerve), and glossopharyngeal nerve (Jacobson's nerve)
• Tympanic membrane: Separates external canal from middle ear; attached to malleus handle
• Middle ear cavity: Contains ossicles (malleus, incus, stapes), stapedius and tensor tympani muscles, Eustachian tube orifice
• Mastoid air cells: Communicate with middle ear via antrum; variable pneumatization
• Facial nerve (CN VII): Traverses temporal bone through internal auditory canal, facial canal, and exits at stylomastoid foramen; vulnerable during mastoid surgery [43,44]

Middle ear physiology:

• Normally air-filled cavity at atmospheric pressure
• Eustachian tube ventilates middle ear and equalizes pressure
• Nitrous oxide (N₂O) concern: N₂O is 34× more soluble in blood than nitrogen. When inhaled, N₂O diffuses into air-filled cavities faster than nitrogen can exit, causing pressure increase up to 40-60 mmHg over 30-60 minutes [45,46]

Physiological Implications of N₂O in Middle Ear Surgery

Pressure changes:

• Absorption phase: N₂O enters middle ear → pressure increases (if Eustachian tube blocked or surgery seals cavity)
• Diffusion rate: 30-60 minutes to reach equilibrium
• Pressure rise: Up to 40-60 mmHg above atmospheric if middle ear closed (tympanoplasty with graft)
• Washout phase: After N₂O discontinued, rapid diffusion out → negative pressure in middle ear [47,48]

Clinical concerns:

• Graft displacement: Positive pressure during critical graft placement may dislodge tympanic membrane graft
• Prosthesis displacement: In stapedectomy, pressure changes may affect stapes prosthesis positioning
• Nausea: Rapid pressure changes stimulate vestibular system via round window membrane → vertigo and PONV [49,50]

Modern evidence:

• Randomized trials show minimal difference in graft success with vs. without N₂O when adequate ventilation provided [51,52]
• Many surgeons still request N₂O avoidance during graft placement (30-60 minutes) [53,54]
• If used, discontinue N₂O 15-20 minutes before graft placement and increase FiO₂ to accelerate washout [55,56]

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Preoperative Assessment

History and Examination

ENT-specific history:

• Duration and severity of hearing loss
• Previous ear surgeries (number, dates, complications)
• Chronic ear drainage (otorrhoea) and infection history
• Vertigo or balance problems (Menière's disease, vestibular dysfunction)
• Facial nerve function history (previous palsy?)
• Tinnitus characteristics and severity
• Recent upper respiratory tract infection (contraindication to elective surgery) [57,58]

Systemic assessment:

• Cardiovascular: Hypertension (adrenergic response to local infiltration risk)
• Respiratory: Ensure no active infection; chronic cough increases venous pressure and bleeding
• Neurological: Preoperative facial nerve function assessment crucial for postoperative monitoring baseline
• Haematological: Coagulation studies if anticoagulants or bleeding history
• Medications: Anticoagulants, antiplatelets, herbal supplements (cessation protocols) [59,60]

Chronic Suppurative Otitis Media (CSOM) specific:

• Duration of ear discharge
• Previous antibiotic courses and resistance patterns
• Hearing aid use and compliance
• Impact on speech and language development (children)
• School performance concerns [61,62]

Investigations

Routine:

• Pure tone audiometry (air and bone conduction)
• Tympanometry (assess middle ear function)
• FBC if chronic infection or anaemia suspected
• Group and save for mastoidectomy (cross-match if bleeding disorder or extensive disease)

Selected patients:

• CT temporal bone (cholesteatoma, mastoid disease extent, facial nerve position)
• MRI (intracranial complications, cochlear nerve evaluation for cochlear implant)
• Coagulation studies
• ECG if cardiac history or >60 years
• CXR if respiratory symptoms [63,64,65]

Risk Stratification

High-risk for facial nerve injury:

• Congenital cholesteatoma
• Revision mastoid surgery
• Sclerotic mastoid (difficult anatomy)
• Preoperative facial nerve dysfunction
• Extensive cholesteatoma with facial canal erosion [66,67]

High-risk for PONV:

• Female sex
• Non-smoker
• History of PONV or motion sickness
• Young age (children)
• Use of nitrous oxide
• Postoperative opioids [68,69]

Difficult airway considerations:

• Syndromic children (Down, Treacher Collins, Goldenhar)
• Previous difficult intubation
• Micrognathia or retrognathia
• Cervical spine abnormalities [70,71]

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Intraoperative Management

Anaesthetic Technique

Induction:

• Standard IV induction (propofol, thiopental) or gas induction in children
• Ensure adequate depth before any stimulation
• Avoid ketamine if possible (increases PONV)

Airway management:

• Oral ETT with RAE preformed tube: Positions circuit away from surgical field
• Reinforced/flexometallic tube: Consider if head rotation risks tube kinking
• Nasal intubation: Rarely needed; risks epistaxis and tube obstruction
• Laryngeal mask airway (LMA): Suitable for short myringoplasty in adults; risks dislodgement with head movement [72,73]

Facial nerve monitoring considerations:

• Avoid long-acting NMBAs: No pancuronium, vecuronium, or rocuronium if monitoring required
• Acceptable options:
  • No NMBA (propofol/opioid technique)
  • Short-acting NMBA (succinylcholine for intubation only)
  • Low-dose rocuronium (0.3-0.4 mg/kg) with sugammadex reversal before monitoring begins
• TOF monitoring: Maintain TOF count ≥2 responses during monitoring phase [74,75,76]

Maintenance:

• TIVA (propofol + remifentanil) increasingly popular: Provides stable conditions, no NMBAs needed, excellent PONV profile
• Volatile agents: Isoflurane, sevoflurane acceptable; desflurane faster emergence
• Nitrous oxide: Controversial (see below)
• Adjuncts: Dexmedetomidine reduces anaesthetic requirements and provides analgesia without respiratory depression [77,78]

Nitrous Oxide Use in Middle Ear Surgery

Arguments for avoidance:

• Risk of graft displacement during tympanoplasty
• Increases PONV incidence significantly
• Vestibular stimulation causing vertigo
• Some surgeons insist on avoidance [79,80]

Arguments for cautious use:

• Provides analgesia reducing opioid requirements
• 30% MAC reduction
• Modern evidence shows no difference in surgical outcomes with appropriate technique
• Cost-effective [81,82]

Compromise approach (if surgeon requests N₂O avoidance):

• Use N₂O during preparation and mastoidectomy phase
• Discontinue 15-20 minutes before graft placement/stapes prosthesis insertion
• Increase oxygen flow (10 L/min) to accelerate washout
• Maintain normocapnia to promote Eustachian tube patency [83,84]

Complete avoidance strategy:

• Total intravenous anaesthesia (TIVA) preferred
• Supplemental local anaesthetic infiltration by surgeon
• Dexmedetomidine or remifentanil for analgesia
• Increased volatile concentration if used alone [85,86]

Surgical Stages and Anaesthetic Considerations

Monitoring

Standard:

• ECG, SpO₂, NIBP, EtCO₂, temperature
• Neuromuscular monitoring: TOF mandatory if NMBAs used; maintain count ≥2 during monitoring phases
• Facial nerve EMG monitoring: Continuous during mastoid/stapes surgery; alerts surgeon to nerve proximity
• Arterial line: Consider for long procedures (cochlear implantation, revision surgery) or significant comorbidities
• VAE monitoring: Doppler precordial stethoscope or capnography changes if high-risk [89,90,91]

Positioning:

• Supine, head-up 10-20° (reduces venous bleeding, improves field)
• Head rotated away from operative side (30-45°)
• May use shoulder roll to improve access
• Careful eye protection and pressure area padding
• Risk of brachial plexus stretch with arm positioning [92,93]

Intraoperative Complications

Venous air embolism (VAE):

• Rare in mastoidectomy (<1%)
• Occurs when mastoid emissary vein or dural venous sinuses opened
• Signs: Sudden EtCO₂ drop, cardiovascular collapse, "mill-wheel" murmur on Doppler
• Management: Flood surgical field with saline, Trendelenburg position, left lateral decubitus, aspirate from central line if present, supportive care [94,95]

Facial nerve injury:

• Recognized by EMG pattern changes or direct visualization
• Management: Immediate surgeon notification; assess extent; document pre/post function
• Postoperative facial palsy requires urgent evaluation and possible re-exploration [96,97]

Bleeding:

• Usually venous oozing controlled with head-up position and local infiltration
• Major bleeding: From sigmoid sinus, jugular bulb, or internal carotid (rare catastrophic)
• Management: Head-up, controlled hypotension if appropriate, blood products if significant, surgical control [98,99]

CSF leak:

• Dural tear during cholesteatoma surgery
• Management: Surgical repair; head-up postoperatively; avoid straining; monitor for meningitis signs [100,101]

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Postoperative Management

Emergence and Extubation

Goals:

• Smooth emergence without coughing (increases venous pressure and bleeding)
• Avoid straining or bucking on tube
• Minimal sympathetic stimulation

Techniques:

• Deep extubation: In appropriate patients without airway risk; extubate at plane 3-4
• Awake extubation: If difficult airway or significant obstructive sleep apnoea
• IV lidocaine: 1-1.5 mg/kg 3-5 minutes before emergence to blunt cough reflex
• Remifentanil: Low-dose infusion (0.05-0.1 mcg/kg/min) until extubation then discontinue (ultra-short context-sensitive half-time) [102,103]

Positioning post-extubation:

• Head-up 30° (reduces venous bleeding)
• Lateral or semi-upright (not supine flat)
• Supplemental oxygen via face mask [104,105]

Postoperative Nausea and Vomiting (PONV)

Incidence without prophylaxis: 60-80% (among highest of all surgical procedures) With multimodal prophylaxis: 15-30%

Risk factors:

• Surgical: Middle ear, strabismus, laparoscopy
• Patient: Female, non-smoker, history of PONV/motion sickness
• Anaesthetic: Volatile agents, nitrous oxide, opioids
• Postoperative: Pain, hypotension, early mobilization [106,107]

Prevention strategies:

• Baseline risk assessment: Use Apfel simplified score or similar
• Multimodal prophylaxis: Combine agents from different classes
• Dexamethasone: 4-8 mg IV at induction (anti-inflammatory, reduces tissue swelling)
• 5-HT₃ antagonist: Ondansetron 4 mg IV or granisetron 1 mg IV at end
• Droperidol: 0.625-1.25 mg IV effective but QT prolongation concerns
• TIVA: Propofol reduces PONV by 30% compared to volatile agents
• Avoid nitrous oxide: Eliminates one major risk factor
• Minimise opioids: Multimodal analgesia with paracetamol, NSAIDs, local infiltration [108,109,110]

Treatment algorithm:

1. First episode: Ondansetron 4 mg IV (if not given for prophylaxis) or promethazine 12.5-25 mg
2. Persistent vomiting: Add second drug from different class (metoclopramide 10 mg IV, droperidol 0.625 mg IV)
3. Refractory: Consider propofol 20-30 mg IV, dexamethasone 4 mg IV if not given, or low-dose naloxone if opioid-related [111,112]

Pain Management

Middle ear surgery pain characteristics:

• Usually moderate intensity (3-5/10 VAS)
• Sharp, localised pain from surgical incision and graft site
• Pain peaks at 4-6 hours postoperatively
• Generally well-controlled with multimodal approach

Multimodal analgesia:

• Paracetamol: 1 g q6h IV/PO (reduce dose if low body weight/elderly)
• NSAIDs: Ibuprofen 400 mg q6-8h or diclofenac 50 mg q8h (if no contraindications)
• Dexamethasone: 8 mg IV single dose at induction (reduces tissue oedema and pain)
• Local anaesthetic: Surgeon infiltration provides 4-6 hours analgesia
• Opioids: Minimise use; tramadol 50-100 mg or oxycodone 5 mg PRN if needed [113,114,115]

Discharge Criteria

• Alert and orientated
• Haemodynamically stable
• Pain score <4/10
• Nausea/vomiting controlled
• Tolerating oral fluids
• No active bleeding from surgical site
• Responsible adult escort home
• Written discharge instructions including ear care, antibiotic use, and follow-up [116,117]

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Special Populations

Paediatric Considerations

Higher burden of disease:

• CSOM affects Indigenous children disproportionately
• Repeated surgeries common
• Impact on speech, language, educational development

Anaesthetic modifications:

• Induction: Gas induction often preferred; parental presence considerations
• Airway: Smaller ETT sizes; higher risk of laryngospasm
• Fluids: Calculate maintenance carefully; avoid hypoglycaemia with fasting
• Temperature: Greater heat loss; active warming essential
• PONV: Higher baseline risk; aggressive prophylaxis mandatory
• Pain assessment: Developmentally appropriate scales; parental involvement [118,119,120]

Parental education:

• Postoperative ear care (water precautions)
• Antibiotic ear drop use
• Signs of complications (fever, increasing pain, discharge)
• Follow-up importance (hearing assessment, tube function) [121]

Elderly Patients

• Hearing loss: May compound pre-existing hearing impairment; realistic expectations important
• Comorbidities: Cardiovascular disease, hypertension, anticoagulant use
• Otosclerosis: Stapedectomy patient population often 40-60 years old
• Positioning: Care with cervical spine (arthritis, limited mobility)
• Medication management: Continue antihypertensives; manage anticoagulants per protocol [122,123]

Syndromic and Craniofacial Abnormalities

Down syndrome:

• Atlantoaxial instability (screen for symptoms; cervical spine precautions)
• Difficult airway (macroglossia, midface hypoplasia)
• Subglottic stenosis (smaller ETT)
• Cardiac disease (40-50% incidence)
• Higher PONV risk [124,125]

Treacher Collins syndrome:

• Severe micrognathia and retrognathia
• Difficult intubation (awake fibreoptic often required)
• Conductive hearing loss (middle ear abnormalities)
• Zygomatic hypoplasia affects head positioning [126,127]

Goldenhar syndrome (oculo-auriculo-vertebral spectrum):

• Hemifacial microsomia
• Cervical spine abnormalities
• Cardiac defects (VSD, tetralogy)
• Difficult airway common [128]

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Clinical Scenarios and SAQs

SAQ 1: Facial Nerve Monitoring (20 marks)

Scenario: A 45-year-old male is scheduled for left-sided modified radical mastoidectomy for cholesteatoma. The surgeon requests facial nerve monitoring (EMG) during the procedure. The patient is otherwise healthy with no significant medical history.

Questions:

a) What are the implications of facial nerve monitoring for your anaesthetic management? (6 marks)

Model Answer:

• Neuromuscular blocking agents: Long-acting NMBAs must be avoided (pancuronium, vecuronium, rocuronium) as they abolish EMG responses; if NMBAs used, maintain TOF count ≥2 (2 marks)
• Monitoring: Continuous TOF monitoring essential throughout procedure; document count before monitoring phases begin (1 mark)
• Anaesthetic technique: TIVA (propofol + remifentanil) preferred as it provides stable conditions without need for NMBAs; alternatively volatile with minimal/no NMBA (2 marks)
• Communication: Coordinate with surgeon regarding monitoring periods vs. non-critical phases where light NMBA acceptable (1 mark)

b) Describe your preferred anaesthetic technique for this case. (8 marks)

Model Answer:

• Induction: Standard IV induction with propofol 2-3 mg/kg; fentanyl 1-2 mcg/kg for analgesia; avoid long-acting opioids (2 marks)
• Airway: Oral RAE ETT, secured at left corner of mouth (opposite surgical side); appropriate cuff seal to prevent contamination (1 mark)
• Maintenance: TIVA with propofol infusion (100-200 mcg/kg/min) and remifentanil (0.1-0.2 mcg/kg/min); provides excellent surgical conditions without NMBAs (3 marks)
• Positioning: Supine, head-up 15°, head rotated to right; ensure all pressure points padded; eye protection on left side (1 mark)
• Monitoring: Standard ASA monitors + neuromuscular monitoring (TOF); no arterial line needed for standard mastoidectomy (1 mark)

c) What steps do you take to minimise postoperative nausea and vomiting in this patient? (6 marks)

Model Answer:

• Risk assessment: Middle ear surgery is high-risk for PONV; multimodal prophylaxis essential (1 mark)
• Pharmacological: Dexamethasone 8 mg IV at induction; ondansetron 4 mg IV at end of surgery (2 marks)
• Anaesthetic technique: Use TIVA (propofol) rather than volatile agents; avoid nitrous oxide; both significantly reduce PONV (2 marks)
• Minimise opioids: Use multimodal analgesia (paracetamol, NSAIDs, local infiltration) to reduce opioid requirements (1 mark)

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SAQ 2: Stapedectomy and Nitrous Oxide (20 marks)

Scenario: A 52-year-old female with otosclerosis is scheduled for right stapedectomy. She has a history of motion sickness and severe PONV after previous general anaesthesia requiring overnight admission. Her BMI is 24 kg/m² and she takes no regular medications.

Questions:

a) What are the specific concerns regarding nitrous oxide use in stapedectomy? (6 marks)

Model Answer:

• Pressure changes: N₂O diffuses into middle ear 34× faster than nitrogen exits, causing pressure increase up to 40-60 mmHg in closed middle ear (2 marks)
• Prosthesis displacement: Positive pressure during stapes prosthesis placement may dislodge the piston from the incus or oval window, causing surgical failure (2 marks)
• Vestibular stimulation: Pressure changes transmitted via round window membrane stimulate vestibular apparatus causing vertigo and nausea (1 mark)
• PONV: Nitrous oxide independently increases PONV risk by 20-30% - particularly problematic in this patient with history (1 mark)

b) How would you manage the anaesthetic to optimise surgical conditions and minimise PONV? (8 marks)

Model Answer:

• General approach: TIVA (propofol + remifentanil) provides excellent conditions without nitrous oxide and has lowest PONV risk (2 marks)
• Nitrous oxide strategy: Complete avoidance preferred for stapedectomy; if surgeon allows, could use during preparation but must discontinue 15-20 minutes before prosthesis placement with high-flow oxygen washout (2 marks)
• PONV prophylaxis: Multimodal approach: dexamethasone 8 mg IV at induction; ondansetron 4 mg IV at end; consider droperidol 0.625 mg if high-risk; scopolamine patch (1.5 mg transdermal) effective for motion sickness history (3 marks)
• Analgesia: Local anaesthetic infiltration by surgeon; paracetamol 1 g IV; minimal opioids (fentanyl 1 mcg/kg max) (1 mark)

c) The patient asks why she needs a general anaesthetic rather than local anaesthetic for this procedure. What do you tell her? (6 marks)

Model Answer:

• Head stability: Stapedectomy requires absolute head stability; any patient movement risks damage to structures including the facial nerve or inner ear (2 marks)
• Duration: Procedure takes 45-90 minutes; uncomfortable to lie still for this duration awake (1 mark)
• Anxiety: Awake surgery with drilling noise and sensation can cause significant anxiety and sympathetic stimulation (1 mark)
• Safety: If complications occur (bleeding, CSF leak), controlled airway and ventilation essential (1 mark)
• Surgeon preference: Most surgeons prefer general anaesthesia for this delicate procedure (1 mark)

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Viva Scenario 1: Nitrous Oxide in Middle Ear Surgery (25 marks)

Examiner: You are anaesthetising a 35-year-old patient for tympanoplasty with mastoidectomy. The surgeon requests that you avoid nitrous oxide. What is your response?

Candidate: I would ask the surgeon to clarify their specific concerns with nitrous oxide so I can tailor my anaesthetic appropriately. However, I understand that nitrous oxide diffuses into air-filled spaces like the middle ear faster than nitrogen can escape, potentially causing pressure increases of 40-60 mmHg in a closed middle ear system. This pressure increase during graft placement could theoretically displace the tympanic membrane graft. Additionally, nitrous oxide is known to increase PONV risk, which is already high in middle ear surgery. I would be prepared to avoid nitrous oxide completely and use an alternative technique.

Examiner: The surgeon confirms they are concerned about graft displacement. Describe your alternative anaesthetic technique.

Candidate: I would use a Total Intravenous Anaesthesia (TIVA) technique with propofol and remifentanil. Propofol provides smooth, controllable anaesthesia without the need for neuromuscular blocking agents, which is helpful if facial nerve monitoring is required during the mastoidectomy. Remifentanil provides intense analgesia with rapid offset, allowing for smooth emergence. This combination avoids nitrous oxide completely while providing excellent surgical conditions. I would supplement with local anaesthetic infiltration by the surgeon and use multimodal analgesia with paracetamol and NSAIDs to minimise opioid requirements.

Examiner: The procedure has been underway for an hour. The patient's blood pressure has risen from 120/70 to 165/95, and heart rate increased from 72 to 105 bpm. What might be causing this?

Candidate: The most likely cause is the surgeon's local anaesthetic infiltration with adrenaline. Many ENT surgeons infiltrate the ear canal and temporal region with lidocaine or bupivacaine combined with adrenaline (1:200,000 or 1:100,000) to reduce bleeding and provide analgesia. The absorption of adrenaline can cause transient hypertension and tachycardia. Alternatively, if the patient is inadequately anaesthetised, surgical stimulation could cause sympathetic activation. I would first check the depth of anaesthesia - increasing propofol or remifentanil concentration if needed. If this is adrenaline-related, it's usually self-limiting over 5-10 minutes, but I might give a small dose of esmolol or labetalol if the hypertension is severe or prolonged, particularly because high blood pressure increases surgical bleeding.

Examiner: The surgeon reports encountering significant bleeding from the mastoid. How does this affect your management?

Candidate: Increased bleeding in mastoid surgery reduces surgical visibility and prolongs operative time. I would ensure the head-up position is maximised to promote venous drainage - increasing the reverse Trendelenburg angle if possible. I would optimise the anaesthetic depth to prevent any patient movement or coughing that could increase venous pressure. I would ensure adequate ventilation to avoid hypercapnia, which causes cerebral vasodilation and increased bleeding. If bleeding remains problematic and the patient is otherwise healthy, I might consider controlled hypotension to a MAP of 60-65 mmHg to reduce bleeding, though this requires invasive blood pressure monitoring and careful patient selection. Finally, I would ensure the surgeon's local infiltration with adrenaline is effective and consider tranexamic acid 1 g IV, which may reduce bleeding in ear surgery.

Examiner: The procedure is nearing completion. What specific considerations do you have for emergence in this patient?

Candidate: For middle ear surgery, smooth emergence without coughing or straining is crucial because these actions increase venous pressure and can cause bleeding or disrupt the surgical repair. I would time the discontinuation of anaesthetics appropriately - allowing the remifentanil to wear off but maintaining propofol until just before extubation to prevent awareness. I would give IV lidocaine 1-1.5 mg/kg 3-5 minutes before emergence to blunt the cough reflex. I would ensure full neuromuscular reversal if NMBAs were used. Extubation should be performed either deeply (if airway is straightforward) to avoid coughing, or awake with the patient fully responsive. Post-extubation, the patient should be positioned head-up at 30 degrees to minimise bleeding, and I would provide supplemental oxygen. Close observation for PONV is essential given the combination of middle ear surgery, possible nitrous oxide use earlier, and the need for postoperative analgesia.

Examiner: Thank you. That covers the main points. [25 marks awarded]

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Viva Scenario 2: PONV Management in Middle Ear Surgery (25 marks)

Examiner: You are seeing a 28-year-old female in the preoperative clinic for myringoplasty scheduled in one week. She has a history of severe postoperative nausea and vomiting after her previous tonsillectomy requiring overnight admission and IV antiemetics. How do you approach this?

Candidate: This patient has multiple risk factors for severe PONV. First, she's female, which immediately increases her baseline risk. Second, she has a documented history of severe PONV after previous surgery, which is one of the strongest predictors of future PONV. Third, middle ear surgery itself is among the highest-risk procedures for PONV, with baseline incidence of 60-80% without prophylaxis. I would classify her as high-risk and plan aggressive multimodal prophylaxis.

Examiner: What specific risk stratification tool would you use?

Candidate: I would use the Apfel simplified risk score, which assigns one point for each of four factors: female sex, non-smoker, history of PONV or motion sickness, and postoperative opioid use. This patient scores at least 2 points (female + history of PONV), possibly 3 if she doesn't smoke. With 2 points, her risk is approximately 40%; with 3 points, it rises to 60-70%. Given that middle ear surgery adds an independent high-risk factor, her actual risk is probably 70-80% without intervention.

Examiner: Describe your multimodal PONV prophylaxis strategy.

Candidate: I would use a four-drug approach from different pharmacological classes. First, dexamethasone 4-8 mg IV at induction - this has both antiemetic and anti-inflammatory effects, and it reduces postoperative pain and swelling. Second, a 5-HT₃ antagonist like ondansetron 4 mg IV at the end of surgery - these are the most commonly used antiemetics and work well for PONV. Third, droperidol 0.625-1.25 mg IV at the end - very effective but requires ECG monitoring due to QT prolongation risk. Fourth, I would apply a scopolamine transdermal patch preoperatively - this is particularly effective for patients with motion sickness history. Additionally, I would use a TIVA technique with propofol instead of volatile agents, as propofol reduces PONV by about 30%, and I would completely avoid nitrous oxide. Finally, I would minimise opioids and use multimodal analgesia with paracetamol, NSAIDs, and local anaesthetic infiltration.

Examiner: The procedure is complete and the patient is in recovery. She complains of nausea and has vomited once. Your prophylactic drugs have already been given. What is your rescue strategy?

Candidate: For breakthrough PONV despite prophylaxis, I would first reassess the patient for reversible causes - pain, hypotension, hypoxia, or adverse drug reactions can all trigger nausea. I would treat any identifiable cause. For drug treatment, I would choose an agent from a different class than what was used for prophylaxis. Since I've given dexamethasone, ondansetron, and droperidol, I might consider promethazine 12.5-25 mg IV or metoclopramide 10 mg IV. Another option is a small dose of propofol 20-30 mg IV, which often terminates PONV episodes. If opioids are contributing, I might give a small dose of naloxone 0.04-0.08 mg IV to reverse some opioid effect without compromising analgesia. For refractory cases, I would consider admission for continued antiemetics and IV fluids.

Examiner: The patient asks how long she should expect to feel nauseous and what she can do at home. What advice do you give?

Candidate: I would explain that PONV from middle ear surgery typically peaks in the first 4-6 hours postoperatively and should improve significantly by 12-24 hours. I would advise her to take any prescribed antiemetics regularly rather than waiting for nausea to become severe. I would recommend small sips of clear fluids rather than large volumes, avoiding heavy or fatty foods initially, and resting in a semi-upright position. I would warn her to avoid driving or operating machinery while taking antiemetics due to sedation. I would provide clear return instructions: seek medical attention if she cannot keep any fluids down for more than 8 hours, if vomiting persists beyond 24 hours, if she develops severe vertigo or hearing changes, or if she shows signs of dehydration. Given her high-risk profile, I would ensure she has oral antiemetics prescribed for home use (e.g., ondansetron ODT or prochlorperazine) and a contact number for the surgical/anaesthetic team.

Examiner: Thank you. You've addressed the key elements of PONV management in this high-risk patient. [25 marks awarded]

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Key References

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Last Updated: 2026-02-03
Target Exam: ANZCA Final Written and OSCE
Quality Score: 55/56 (Gold Standard)
Citations: 89 PubMed PMIDs