Airway Management

Unanticipated Difficult Airway

The basic premise in an unanticipated difficult airway is that the goal of airway management is oxygenation, not intubation.
Management of difficult airway should be practiced and protocols exist to avoid task fixation and to enable practitioners to overcome the anxiety of performing front of neck access.
For resources on unanticipated difficult airway please refer to the Difficult Airway Society Guidelines as well as the VORTEX approach. For anticipated difficult airway, consider the ASA guidelines.

Anticipated Difficult Airway

There are many ways to manage an anticipated difficult airway but it is less well discussed in the literature compared to an unanticipated difficult airway.
An anticipated difficult airway is a difficult airway that is predicted based on the combination of history, examination and investigations. These patients require a different approach to airway management.
Refer to ANZCA Airway Assessment document for further reading on airway assessment and management, including discussions on three column theory.

Airway Assessment

Assess for:

1. Patient co-operation or consent
2. Aspiration risk
3. Difficult mask ventilation (MOANS)
  1. - Mask seal (facial hair)
    - Obesity (BMI > 26)
    - Age > 55 years
    - No teeth
    - Snoring (OSA)
    - Radiation therapy
4. Difficult LMA placement
5. Difficult laryngoscopy and Intubation
  1. - TMD and MP has 36% sens
    - According to three column model:
      - Anterior column (decreased volume/compliance)
        Limited mouth opening (inter-incisor distance <37 mm)
        MP 3/4
        TMD < 6.5 cm
        Limited jaw protrusion
        Large tongue
      - Middle column (History/CXR/CT/FNE)
        Epiglottitis/burns
        Foreign bodies
        Cancers
      - Posterior column
        Short neck
        Large neck circumference >43 cm
        Decreased neck mobility < 90 degrees
6. Difficult surgical airway

Airway Management

Consider airway options:
1. - BMV
  - LMA
  - ETT
  - Others
If intubating, consider the options of:
1. - Will an ETT solve the airway issue?
  - Awake intubation vs asleep
  - Non-invasive vs invasive techniques
  - Spontaneously breathing vs paralysed
Develop primary and alternative strategies, including plans for:
1. - Primary intubation (PLAN A)
  - LMA insertion (PLAN B)
  - Can ventilate, cannot intubate (PLAN C)
  - Cannot ventilate, cannot intubate (PLAN D)
The goal is to maintain oxygenation by ensuring the delivery supplemental oxygen throughout the process via facemask/HFNP or LMA.
Preparation (CIMADEP):
1. - Consent
  - IV Access
  - A: Brief assistant of plan, get second anaesthetist, get ENT
  - D: Emergency and non-emergency drugs drawn up.
  - E: Difficult airway trolled, Bronchoscope, Plan D kit checked, neck marked and prepped.
  - Pre-oxygenation
Consider intubating techniques depending on the problem by assessing the anterior, middle and posterior column issues:
1. - Anterior column
    - Optimise head and neck position
    - Straight laryngoscopes (Millers)
    - Videolaryngoscopes
    - Intubating LMA
    - Fibreoptic intubation
  - Middle column
    - Caution fibreoptic devices may be more difficult to use due to narrowing or upper airway and may lead to total airway occlusion
    - Direct laryngoscopy/videolaryngoscopy (consider spontaneous breathing techniques)
    - Intubating LMA
    - Awake tracheostomy
  - Posterior column
    - Videolaryngoscopes (especially hyperangulated blades CMAC-D)
    - Specialised laryngoscopes (e.g McCoy, etc)
    - Intubating LMA
    - Adjuncts (stylets, bougies)
    - Fibreoptic intubation

Key questions:

Inability to cooperate or unwilling to consent to awake
- Asleep
High aspiration risk:
- Asleep with RSI
- Awake techniques
Airway access
- Limited mouth opening
  - Nasal fibreoptic route
  - Surgical airway
- Glottic/supraglottic obstruction
  - Tracheostomy
- Base of skull fracture
  - Oral route
  - Surgical airway
Urgency
- Imminent airway loss
  - Asleep + full paralysis
  - Surgical airway
- Semi-elective
  - Spontaneous breathing/paralysis
  - Asleep > awake
  - Surgical airway
Easy BMV and:

1. Easy laryngoscopy
  1. Asleep techniques
  2. +/- Optiflow
2. Difficult laryngoscopy
  1. Videolaryngoscopy
  2. Fibreoptic
    1. Spontaneous breathing - asleep or awake, TIVA/volatile
    2. Paralysed
  3. Tracheostomy
  4. +/- Optiflow

Ease of supraglottic airway
In all cases, consider:

1. Location
2. Additional help from ENT/second anaesthetist/second anaesthetic nurse
3. Difficult airway trolley
4. Optiflow THRIVE
5. LMA rescue/conduit
6. Emergency surgical airway

Options:

Awake vs asleep intubation
1. Awake if likely difficult BMV and laryngoscopy, cooperative, airway not compromised or risk of aspiration present.
  1. Allows maintenance of ventilation and airway patency, some protection against aspiration, option to abort.
  2. AFOI
    1. Time consuming, may require sedation
    2. Patient refusal/non-compliant, bleeding airway, some tumours in upper airway may bleed and obstruct vision, allergy to LA
  3. Awake tracheostomy
    1. If AFOI likely difficult (presence of blood/pus in airway)
    2. If glottic or supra-glottic obstruction present
    3. If airway compromise a long term issue
2. Asleep
  1. Maintaining spontaneous ventilation via inhalational or Propofol TIVA if difficult BMV or laryngoscopy, un-cooperative, low risk of aspiration, airway not immediately compromised
    1. Maintenance of ventilation and oxygenation and option to wake-up.
    2. Risk of apnoea, laryngospasm, aspiration, airway collapse and time consuming
  2. Ablating spontaneous ventilation
    1. If BMV is expected easy but laryngoscopy/intubation difficult
    2. If at risk of aspiration = RSI
      1. Have plan A and B prepared
      2. Establish exit strategy (wake-up, facemask and surgical cricothyroidotomy)
Elective bypass/ECMO
1. If induction of anaesthesia likely leads to complete airway obstruction, difficult BMV, difficult laryngoscopy and intubation.
Worst case scenario:
1. Difficult BMV + laryngoscopy + intubation + aspiration risk + uncooperative patient
2. RSI + videolaryngoscopy/asleep FOB + THRIVE + ENT for cricothyrodotomy

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