Key Facts

Airway management is the primary responsibility of the anaesthetist. Failure to maintain the airway is the leading cause of anaesthesia-related mortality. Structured assessment, planning, and use of algorithms are essential for safe practice.

Epidemiology

NAP4 (4th National Audit Project, 2011) found that airway complications accounted for approximately 60% of anaesthesia-related deaths. CICO events occurred in approximately 1 in 50,000 anaesthetics. Poor airway management in ICU was highlighted as a significant contributor to adverse outcomes.

Aetiology

Difficult airway situations arise from:

• Anatomical factors: Obesity, short neck, receding mandible, large tongue, limited mouth opening, cervical spine immobility
• Pathological factors: Head/neck tumours, previous radiotherapy, burns, trauma, infection (Ludwig's angina, epiglottitis)
• Physiological factors: Pregnancy (oedema, reduced FRC), obesity (rapid desaturation)

Pathophysiology

The upper airway functions as a conduit for ventilation. During anaesthesia, loss of muscle tone causes posterior displacement of the tongue and epiglottis, obstructing the airway. The goal of airway management is to maintain a patent airway for oxygenation and ventilation while protecting the lungs from aspiration.

Airway Assessment (Pre-operative)

• Mallampati score (I-IV): Assess oropharyngeal view
• Thyromental distance: <6.5cm suggests difficult intubation
• Mouth opening: <3 finger-breadths concerning
• Neck mobility: Reduced extension limits intubation
• Body habitus: BMI, neck circumference
• Dental assessment: Loose teeth, prominent incisors, dental prosthetics

Signs of Airway Obstruction

• Snoring, gurgling, stridor
• See-saw (paradoxical) breathing
• Use of accessory muscles
• Desaturation
• Absent or reduced breath sounds

Airway Devices (Escalation)

1. Basic manoeuvres: Head tilt-chin lift, jaw thrust
2. Oropharyngeal (Guedel) or nasopharyngeal airway
3. Supraglottic airway device (SGA/LMA)
4. Endotracheal tube (ETT)
5. Emergency front-of-neck access (cricothyroidotomy)

Red Flags

• Rapid desaturation despite airway manoeuvres - escalate immediately
• Cannot intubate, cannot oxygenate - declare CICO, perform eFONA
• Stridor pre-operatively - suggests significant airway compromise
• Expanding neck haematoma - secure airway urgently before complete obstruction

Bedside

• Airway assessment: Mallampati, thyromental distance, mouth opening, neck extension, dentition
• Capnography (ETCO2): Gold standard for confirming ETT placement - trace confirms tracheal position
• SpO2: Continuous monitoring during airway management
• Auscultation: Bilateral chest and epigastrium after intubation

Bloods

• Not specific to airway management

Imaging

• Neck X-ray/CT: If cervical spine injury or retropharyngeal abscess suspected
• CT neck: Pre-operative planning for known difficult airway (tumour, tracheal deviation)
• CXR: Post-intubation to confirm ETT position (tip at T2-T4 level)
• Nasendoscopy: For anticipated difficult airway - ENT assessment of upper airway anatomy

Special Tests

• Fibreoptic intubation: Awake fibreoptic nasotracheal intubation for anticipated difficult airway
• Point-of-care ultrasound: Identify cricothyroid membrane, assess airway anatomy

Non-pharmacological

• Positioning: Ramped position (ear-to-sternal notch alignment) - improves laryngoscopy, essential in obese patients
• Pre-oxygenation: 100% O2 for 3 minutes (or 8 vital capacity breaths) - extends safe apnoea time
• Apnoeic oxygenation: Nasal high-flow O2 (THRIVE) during laryngoscopy - extends safe apnoea time

Pharmacological

• Induction: Propofol 2-3mg/kg or thiopental 3-5mg/kg
• Neuromuscular blockade: Rocuronium 0.6-1.2mg/kg or suxamethonium 1-1.5mg/kg (RSI)
• Sugammadex 16mg/kg: Immediate reversal of rocuronium in CICO/failed intubation scenarios
• Topical LA: 4% lidocaine spray for awake intubation
• Antisialagogue: Glycopyrrolate 200mcg IV for awake fibreoptic intubation

Surgical/Interventional

• Scalpel cricothyroidotomy (eFONA): For CICO - DAS recommends scalpel-bougie-tube technique
• Surgical tracheostomy: Planned or emergency for prolonged ventilation or known difficult airway
• Percutaneous tracheostomy: ICU - typically at 7-10 days of intubation

Referral Criteria

• Known or anticipated difficult airway - senior anaesthetist planning, ENT standby
• Failed intubation - follow DAS algorithm, consider wake-up or alternative plan
• CICO event - critical incident reporting, post-event debrief, psychological support for team

• NAP4 findings: Airway complications are responsible for ~60% of anaesthesia-related deaths
• CICO frequency: ~1 in 50,000 anaesthetics; eFONA success rate >90% when performed promptly
• Failed intubation: Occurs in ~1 in 2,000 routine anaesthetics; higher in obstetrics (~1 in 400)
• Aspiration: Mortality ~5% when it occurs; risk factors include emergency surgery, obesity, pregnancy
• Videolaryngoscopy: Reduces failed intubation rates by 50% compared with direct laryngoscopy

Mallampati Classification

DAS Failed Intubation Algorithm (Simplified)

Cormack-Lehane Grading