FRCA Notes

Airways in Critical Care

Resources

  • 25% of difficult airways occur in critical care (NAP4)
  • 45% of critically ill patients experience at least one major adverse event during intubation (INTUBE study, 2018), of which cardiovascular instability is the most frequent
  • A number of factors increase the risk of difficult intubation in critically unwell patients
Factor Notes
Difficult airway Airway assessment may be challenging
May require MILS or other C-spine immobilisation
Limited time for airway manipulation due to hypoxia
Airway trauma or oedema
No ability to wake patient up if failed intubation
Environmental factors Improper positioning
Unfamiliar or missing equipment
Human factors Ad-hoc teams & unfamiliarity
Deviation from standard protocols
Aspiration risk Uncertain or inadequate starvation status
Effect of critical illness, trauma etc. on gastric stasis
Gastric distension from NIV or HFNO
Respiratory pathology Shunt from disease process
Significant hypoxaemia despite pre-oxygenation due to shunt
Cardiovascular pathology Hypotension e.g. from sepsis may contribute to V/Q mismatch
Generally unstable, which limits time
Neurological impairment Agitation or confusion may impair preoxygenation


  • Airway assessment carries low PPV and specificity, and is even more difficult in the critically unwell for a variety of factors
  • The only airway assessment tool validated in the critically ill is the MACOCHA score:
Factor Description Score
Mallampati score III or IV 5
OSA Present 2
C-spine Reduced mobility 1
Mouth Opening <3cm 1
Coma Present 1
Hypoxaemia Sats <80% 1
Non-Anaesthetist As airway operator<80% 1
  • A score ≥3 predicts difficult intubation

  • Other assessment may be warranted e.g.:
    • Nasendoscopy in suspected laryngeal pathology
    • Laryngeal handshake or ultrasound to identify the cricothyroid membrane

  • The above-linked guideline contains significantly more information on the process, but for those wanting abridged notes:

Preparation

  • Use a checklist
  • Optimise positioning and ensure monitoring is in situ
  • Use of HFNO or NIV to pre-oxygenate patients may be beneficial, particularly for those with hypoxaemia
    • In any case pre-oxygenate to end-tidal oxygen concentration >85%
    • If HFNO are used, continue apnoeic oxygenation following induction

Laryngoscopy

  • A failure of 1st pass success (up to 30%) is associated with an increased risk of complications e.g. hyoxaemia (25%), CV instability (25%), cardiac arrest (2%) or death

  • One systematic review found VL did not reduce time to intubation or increase first-pass success, and may even be associated with a higher rate of complications
  • Conversely:
    • A Cochrane systematic review and meta-analysis found VL reduces the number of attempts and the risk of complications
    • A sub-analysis of the INTUBE study found VL was associated with a higher first-pass success rate
    • A recently published multicentre RCT (NEJM, 2023) found VL to have a much higher first-pass success rate, but no difference in complication rate vs. DL

  • Guidelines do not necessarily recommend VL as first-line, but do suggest:
    • Using VL if difficult intubation is anticipated (e.g. MACOCHA ≥3)
    • If initial attempts are with DL and fail, use VL
    • If VL is used as a rescue device, use hyper-angulated VL

Post-intubation

  • Post-intubation recruitment manoeuvres (Pinsp 30-40cmH2O for up to 30s) may improve hypoxia without adverse incidents