2024.2 Day 1 VIVA 9

Airway Management

You are scheduled for an elective endoscopy list in Scenarioville. The next patient is a 60-year-old man booked for a gastroscopy and colonoscopy. He has a BMI of 39 and weighs 110 kg. Although medically complex, he has been cleared for sedation.

There is a known difficult airway alert from a previous intubation, but he has had surgery at a major teaching hospital since then without any reported issues.

Past Medical History:

  • Obesity (weight 170kg previously, 110kg now),

  • Hypertension,

  • Hypercholesterolaemia

  • Obstructive Sleep Apnoea (OSA)

Medications:

  • Olmesartan / Hydrochlorothiazide,

  • Rosuvastatin,

  • Aspirin,

  • Semaglutide - ceased 4 weeks ago.

What are the features of this case that may make airway management difficult?

Patient-Specific Risk Factors:

  • Obesity (BMI 39):

    • Increased risk of rapid desaturation during apnea (reduced FRC)

    • Difficult mask ventilation (poor seal, increased upper airway resistance)

    • Potential for difficult laryngoscopy (anterior larynx, excessive soft tissue)

  • OSA:

    • Higher likelihood of airway collapse under sedation

    • Increased sensitivity to respiratory depressants

  • Previous Difficult Airway Alert:

    • Mandates review of prior anaesthetic records for:

      • Grade of laryngoscopy (Cormack-Lehane)

      • Techniques attempted (videolaryngoscopy, bougie use)

      • Complications encountered (e.g., dental trauma)

  • Semaglutide Use:

    • Despite cessation, residual delayed gastric emptying risk (aspiration precautions needed)

  • Procedure-Specific Challenges:

    • Endoscopy Requirements:

      • Shared airway with endoscopist

      • Potential for gastric insufflation → regurgitation risk

    • Positioning Limitations:

      • Left lateral position may worsen airway mechanics

      • Limited ability to ramp obese patients on endoscopy table

  • Systemic Considerations:

    • Hypertension:

      • May exacerbate hemodynamic swings during induction

    • Aspirin Use:

      • Minor bleeding risk with nasal airway adjuncts

How would you specifically investigate his previous difficult airway?

Immediate Actions:

  • Contact the anaesthetic department where the previous difficult airway was documented to obtain:

    • Detailed anaesthetic chart including laryngoscopy grade (Cormack-Lehane), blade type used, and number of attempts

    • Documentation of any airway rescue techniques employed (e.g., bougie, Frova introducer, video laryngoscopy)

    • Any complications noted (dental damage, esophageal intubation)

  • Review the operative notes from his subsequent surgery at the teaching hospital to determine:

    • Whether standard intubation was successful and what techniques were used

    • Any perioperative airway complications

Physical Reassessment:

  • Compare current vs. previous anthropometric measurements:

    • Weight loss from 170kg to 110kg may improve airway mechanics but does not eliminate risk

    • Current neck circumference (if >40cm = higher risk)

  • Repeat bedside airway assessment (LEMON, Mallampati) to evaluate for changes

What objective measures would you use today to quantify his airway risk?

Structured Airway Assessment:

  • LEMON Method:

    • Look: Assess for facial trauma, beard, dentition (prominent incisors, loose teeth)

    • Evaluate 3-3-2 Rule:

      • Mouth opening <3 fingers breadth = difficult laryngoscopy

      • Thyromental distance <3 fingers = anterior larynx

      • Hyoid-mental distance <2 fingers = difficult alignment

    • Mallampati: Likely Class III/IV due to obesity and OSA

    • Obstruction: Assess for stridor, hoarseness, or paradoxical breathing

    • Neck Mobility: Limited extension increases difficulty

Ultrasound Assessment:

  • Measure skin-to-epiglottis distance (>2.5cm predicts difficult laryngoscopy)

  • Identify cricothyroid membrane preemptively for emergency access

Functional Tests:

  • "Upper Lip Bite Test" to assess mandibular protrusion

  • Assessment of tongue size relative to oropharyngeal space

How would your airway plan differ if he had severe retrognathia?

First-Line Strategy:

  • Awake Fibreoptic Intubation (FOI):

    • Topicalization:

      • Lidocaine 10% spray to oropharynx

      • Bilateral superior laryngeal nerve blocks (2ml 2% lidocaine per side)

      • Transtracheal block (3ml 4% lidocaine)

    • Sedation:

      • Dexmedetomidine infusion (0.5-1 mcg/kg/hr) for cooperative sedation

      • Avoid opioids to maintain respiratory drive

Positioning:

  • Head-up 25° to improve oxygenation

  • Neck flexion with head extension ("sniffing position") if possible

Backup Plans:

  • Videolaryngoscopy with Hyperangulated Blade:

    • GlideScope or C-MAC D-Blade with stylet-loaded ETT

    • Have bougie immediately available

  • Secondary Airway Device:

    • Intubating LMA (e.g., Fastrach) as conduit for intubation

Emergency Preparedness:

  • Pre-identify cricothyroid membrane with ultrasound

  • Have scalpel-bougie kit open and ready

What pre-oxygenation strategy would you use given his comorbidities?

Standard Pre-oxygenation:

  • 100% FiO2 via tight-fitting mask for 3-5 minutes of tidal breathing

  • Target end-tidal O2 >90% (or SpO2 100% for ≥3 minutes)

Augmented Techniques:

  • High-Flow Nasal Oxygen (HFNO):

    • 70L/min flow with FiO2 1.0 during apnea

    • Provides continuous oxygenation and some PEEP

  • Non-Invasive Ventilation (NIV):

    • CPAP 10 cmH2O + PS 5 cmH2O if cooperative

    • Particularly beneficial for OSA patients

Positioning:

  • 25° head-up ramp position to increase FRC

  • "Ear-to-sternal notch" alignment for optimal laryngoscopy

Monitoring:

  • Continuous capnography to confirm adequate pre-oxygenation

  • Pulse oximetry with plethysmographic waveform analysis

How would you mitigate aspiration risk given his semaglutide history?

Pharmacological Prophylaxis:

  • Sodium citrate 0.3M 30ml orally immediately pre-op

  • IV metoclopramide 10mg + pantoprazole 40mg

Mechanical Measures:

  • Rapid sequence induction (RSI) with cricoid pressure

  • Avoid mask ventilation between induction and intubation

Airway Strategy:

  • Prefer videolaryngoscopy for first-pass success

  • Have suction immediately available with Yankauer catheter

Postponement Considerations:

  • If recent food intake suspected, delay case 8 hours

  • Consider ultrasound gastric volume assessment if uncertain

How would you approach sedation versus general anaesthesia for this case?

Decision Framework:

  • Sedation (Propofol TCI):

    • Pros: Faster recovery, lower PONV risk

    • Cons: Higher risk of airway obstruction, hypoxia

    • Criteria: Only if able to maintain spontaneous ventilation + EtCO₂ <6 kPa

  • GA with ETT:

    • Indications: Anticipated prolonged procedure, severe OSA, or failed sedation

Airway Plan for GA:

  • Induction:

    • RSI with ketamine 2mg/kg + rocuronium 1.2mg/kg (avoid suxamethonium in obesity)

    • Backup: Second-generation SGA (i-gel) with gastric drain

  • Maintenance:

    • TIVA (propofol + remifentanil) to minimise respiratory depression

    • Pressure-controlled ventilation (PCV) with PEEP 10 cmH₂O

The patient develops laryngospasm during sedation. How would you manage this?

Immediate Management:

  • Call for assistance and prepare difficult airway trolley

  • 100% O2 with tight mask seal + two-handed jaw thrust

  • Continuous positive airway pressure (CPAP) at 15-20 cmH2O

Pharmacological Intervention:

  • IV propofol 20-50mg boluses to deepen sedation

  • If severe: Suxamethonium 0.5-1 mg/kg IV (prepare for full intubation)

Advanced Maneuvers:

  • Consider nasopharyngeal airway insertion

Post-resolution:

  • Reduce sedation depth by 30%

  • Consider switching to secured airway if recurrent

How would you adjust ventilation during pneumoperitoneum for colonoscopy?

Ventilator Settings:

  • Change to pressure-controlled ventilation (PCV) mode

  • Increase PEEP to 12-15 cmH2O to prevent atelectasis

  • Reduce tidal volumes to 6 mL/kg predicted body weight

  • Permissive hypercapnia (target EtCO2 <8 kPa)

Monitoring:

  • Continuous airway pressure monitoring (peak pressure <35 cmH2O)

  • Regular arterial blood gases if prolonged procedure

Dynamic Strategies:

  • Recruitment maneuvers every 30 minutes (40 cmH2O for 10 seconds)

  • Adjust I:E ratio to 1:1.5 to improve CO2 elimination

What monitoring is essential for safe procedural sedation?

Core Monitoring (ANZCA Minimum Standards):

  • Continuous waveform capnography (nasal cannula or mask sampling)

  • Pulse oximetry with plethysmograph and low-perfusion algorithm

  • ECG with ST-segment analysis

  • Non-invasive blood pressure (3-minute intervals)

Advanced Monitoring:

  • Bispectral Index (BIS) or entropy monitoring for sedation depth

  • Transcutaneous CO2 monitoring in OSA patients

  • Peripheral nerve stimulator if muscle relaxants used

Special Considerations:

  • Direct observation of chest wall movement

  • Continuous communication with patient when possible

The endoscopist requests deeper sedation. How would you respond?

Safety Assessment:

  • Verify airway patency (clear capnography waveform)

  • Check SpO2 (>95%) and EtCO2 (<6 kPa) trends

  • Assess respiratory rate and pattern

Pharmacological Options:

  • Increase propofol TCI target by 0.5 mcg/mL increments

  • Add low-dose remifentanil infusion (0.025-0.05 mcg/kg/min)

Airway Considerations:

  • Insert nasopharyngeal airway prophylactically

  • Have supraglottic airway device prepared

Communication Strategy:

  • Explain risks/benefits to endoscopist

  • Suggest procedural pauses if needed

How would you manage SpO2 dropping to 85% during the procedure?

Immediate Actions:

  • Call for help and activate difficult airway protocol

  • 100% O2 via non-rebreather mask

  • Two-handed jaw thrust with oropharyngeal airway

  • Suction oropharynx under direct vision

Stepwise Escalation:

  • Insert nasopharyngeal airway (size 6.0-7.0mm)

  • Place second-generation SGA (i-gel or LMA Supreme)

  • If ineffective: proceed to endotracheal intubation

Rescue Ventilation:

  • Consider manual ventilation with PEEP valve

  • Limit peak pressures to <20 cmH2O if possible

Post-resuscitation:

  • ABG to assess for hypercapnia/hypoxia

  • Consider ICU admission if prolonged desaturation

Outline your extubation and recovery plan.

Extubation Criteria:

  • Full reversal: TOF ratio >0.9, sustained tetanus, head lift >5 seconds

  • Respiratory: SpO₂ >95% on FiO₂ 0.4, EtCO₂ <6 kPa

  • Hemodynamic: MAP within 20% baseline

High-Risk Extubation Protocol:

  • Positioning: 45° head-up + left lateral tilt

  • Equipment:

    • HFNO at 50L/min post-extubation

    • Second-generation SGA at bedside

  • Pharmacological:

    • IV dexamethasone 8mg to reduce edema

    • Lidocaine 1mg/kg to suppress cough

How would you modify extubation with significant airway edema?

Staged Extubation Approach:

  • Perform leak test around ETT cuff (positive if >25cmH2O pressure)

  • Insert airway exchange catheter (AEC) before extubation

  • Maintain AEC with O2 insufflation (15L/min) for 24 hours

Pharmacological Support:

  • Nebulised adrenaline (5mg in 5ml saline)

  • IV dexamethasone 8mg every 8 hours

Monitoring Plan:

  • ICU admission for continuous monitoring

  • Prepare for possible re-intubation

What are your criteria for PACU discharge?

Modified Aldrete Score ≥9:

  • Activity: Moves all extremities voluntarily

  • Respiration: SpO2 >94% on room air

  • Circulation: BP within 20% of baseline

  • Consciousness: Fully awake and oriented

  • Pain: Score <3/10

OSA-Specific Requirements:

  • No desaturation episodes (<90%) for 30 minutes

  • Able to maintain upright position

  • Observation for 60 minutes after last opioid dose

How would you manage postoperative hypertension (BP 180/100)?

First-Line:

  • Labetalol 5-10mg IV aliquots every 5 minutes

  • Esmolol infusion if tachycardia present

Second-Line:

  • GTN infusion (start at 1mg/hr) if CAD suspected

  • Hydralazine 5-10mg IV if peripheral resistance high

Special Considerations:

  • Avoid beta-blockers in acute cocaine intoxication

  • Monitor for postoperative bleeding if hypertensive

What specific instructions would you give recovery staff?

Monitoring Protocol:

  • Continuous SpO2 with low threshold for CPAP

  • Hourly respiratory rate and pattern assessment

  • Regular sedation scores (e.g., RASS)

Positioning Requirements:

  • Strict 45° head elevation at all times

  • Lateral recovery position encouraged

Escalation Pathway:

  • Immediate anaesthetist review if:

    • SpO2 <90% for >1 minute

    • Respiratory rate <8 or >30

    • New stridor or airway obstruction

How would you manage his OSA overnight?

Positive Airway Pressure Therapy:

  • Mandatory CPAP at preoperative settings if known

  • Auto-titrating CPAP if first-time diagnosis

  • BiPAP if hypercapnic (IPAP 12, EPAP 8 cmH2O)

Monitoring Strategy:

  • High-dependency unit admission

  • Continuous capnography if available

  • ABG at 6 hours post-op

Medication Adjustments:

  • Avoid long-acting opioids

  • Regional analgesia preferred

  • Limit benzodiazepines

Key Learning Points

  1. Obesity and OSA exponentially increase the risk of airway obstruction and rapid desaturation, making both preoxygenation and airway securing strategies critical.

  2. A prior difficult airway mandates thorough review of previous anaesthetic records and tailored planning, including reassessing any changes in weight or anatomy.

  3. Semaglutide use, even if ceased, poses a residual aspiration risk due to delayed gastric emptying, requiring pharmacologic and mechanical prophylaxis.

  4. Awake fibreoptic intubation is the gold standard for anticipated extremely difficult airway, especially in cases of severe retrognathia or significant anatomical distortion.

  5. High-flow nasal oxygen (HFNO) and non-invasive ventilation (NIV) improve apnoea tolerance and preoxygenation efficacy in obese and OSA patients.

  6. During procedural sedation, vigilant monitoring with capnography and readiness to secure the airway are essential, as airway obstruction and laryngospasm are high-risk events.

5 Key Phrases

  1. "This is a shared airway case in a physiologically high-risk patient — planning must be meticulous and multi-tiered."

  2. "My approach is guided by prior records, current anatomy, and structured bedside assessment — including LEMON and airway ultrasound."

  3. "Given the aspiration risk, I would implement a modified rapid sequence induction with videolaryngoscopy as first-line."

  4. "Preoxygenation in a 25-degree head-up position with high-flow nasal oxygen improves both safety and margin for apnoea."

  5. "Intraoperatively, my threshold for transitioning to a secured airway would be low, particularly with any signs of obstruction or desaturation."

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