FRCA Notes

Awake Tracheal Intubation

Awake tracheal intubation has yet to be a Final FRCA CRQ question, though the core curriculum asks us to know 'the indications for fibre-optic intubation and how awake intubation may be achieved'.

The intermediate curriculum follows suit, asking for knowledge of 'the risks associated with awake intubation'.

Resources

  • Induction of general anaesthesia carries risks and consequences with regards to difficult airway management
  • The risk and severity of adverse outcomes during difficult airway management is highlighted by the plethora of guidelines and cognitive aids for airway rescue

  • Asleep airway management strategies are fallible:
    • Plan A: difficult tracheal intubation 1.9 - 10%
    • Plan B:
      • Difficult SAD placement/ventilation 0.5 - 4.7%
      • Success rate of SADs after failed intubation as low as 65%
    • Plan C:
      • Difficult facemask ventilation 0.66 - 2.5%
      • Combined difficult facemask ventilation and tracheal intubation 0.3 - 0.4%
    • Plan D:
      • Requirement for emergency FONA 0.002 - 0.07%
      • Death due to failures of airway management: up to 0.04%

  • Awake tracheal intubation (ATI) should be considered in any patient with predictors of difficult airway management
  • It benefits from:
    • A high success rate of 98 - 99%
    • A low risk profile, as spontaneous ventilation and intrinsic airway tone are maintained
    • Being considered by some to be the gold standard in the management of the predicted difficult airway, yet is currently only used in 0.2% of tracheal intubations

  • Awake intubation must be considered in the presence of predictors of a difficult airway
  • A cognitive aid e.g. checklist is recommended before and during ATI
  • Supplemental oxygen should always be administered
  • Effective topicalisation should be established and tested (max dose lidocaine 9mg/kg LBW)
  • Cautious use of minimal sedation, administered by an independent practitioner
  • Limited to 3+1 attempts
  • Two point check of correct tracheal tube placement prior to inducing anaesthesia (capnography + visual confirmation)
  • All departments should support anaesthetists to attain competency and maintain skills in AFOI

  • (These were asked about explicitly in a practice CRQ, hence meriting their own section)

Indications

  • Should always be considered in the presence of predictors of difficult airway management
Indications for ATI
Patients with head and neck pathology e.g. malignancy, previous surgery, previous radiotherapy
Reduced mouth opening e.g. facial fractures, dental infections
Limited neck extension e.g. C-spine injury
Progressive airway compromise (but not emergency)
OSA or morbid obesity

Contraindications

  • Absolute: patient refusal
  • Relative:
    • LA allergy
    • Lack of adequate equipment or staff
    • Airway contamination e.g. bleeding, friable tumour, open abscess
    • Uncooperative patient
    • Impending airway obstruction (patient is at risk of 'cork in bottle' phenomenon)
    • Grossly distorted anatomy
    • Trauma: fractured base of skill, penetrating eye injury

Consent

  • Patient consent should follow the usual GMC guidance on decision making and consent
  • The process may seem daunting to patients, but in my own experience most patients are agreeable following:
    • A description of the asleep intubation process but why this cannot be performed in them e.g. trismus from infection, facial trauma etc.
    • An honest explanation of the degree of discomfort (most notably during railroading of the tube through the nose)
    • Reassurance that they'll be receiving some form of sedation (if appropriate)

General set up

  • Use of checklist before and during the procedure
  • ATI should be performed in the operating theatre environment, and if there is evidence of high-risk then it should be performed in theatre rather than anaesthetic room
  • Adequate IV access
  • Monitoring as per AAGBI

Feng shui

  • Workplace ergonomics should be optimised - there are nifty diagrams in the DAS guidelines as to suggested set-ups
  • Patient position should be optimised e.g. sitting up or semi-recumbent
  • Position of operators, screens and assistants relative to the patient should be ideal

  • Appropriate route for tracheal intubation should be selected:
    • Nasal e.g. for patients with limited mouth opening
    • Oral e.g. for patients having nasal surgery

Choice of device

  • ATI using videolaryngoscopy (VL) has a comparable success rate (98.3%) to ATI using a flexible bronchoscope (FB)
  • The choice of technique will depend on patient factors and operator factors

  • VL may be more appropriate e.g. if there is airway bleeding
  • FB may be more appropriate e.g. if there is limited mouth opening, fixed flexion deformity or large tongue
  • A combined approach (VAFI) is described too

  • In the above-linked meta-analysis, there was:
    • No significant difference in first-pass success rate between flexible bronchoscopes, videolaryngoscopes (channelled or un-channelled) or optical stylets
    • The shortest time to intubation was with optical stylets (e.g. Bonfils), then VL, then FB
    • No significant difference in the rate of most complications or side-effects

Choice of tube

  • Tube size should factor in: shape | length | tip design | tube material

  • For ATI using flexible bronchoscopy, DAS recommend using either the Parker Flex-Tip or FastTrach ETT, as they are superior to standard PVC tubes
  • One should use the smallest diameter tube possible, as it may reduce incidence of impingement
  • One should position the tube:
    • With the leading edge along the nasal septum during the nasal part
    • With the bevel posteriorly during the remaining process

  • Use of an anti-sialogogue is an optional extra during ATI
Advantages Disadvantages
Reduced airway secretions improves view Tachycardia
Dry mucous membranes ↑ efficacy of topicalisation Increased anxiety 2° to tachycardia
  • Which agent?
    • Options include the standard anti-muscarinic trifecta of glycopyrrolate, atropine or hyoscine
    • The most widely recommended is glycopyrrolate

  • Which dose?
    • DAS suggest 100-200μg of glycopyrrolate 40-60mins pre-procedure
    • The Bristol recipe for ATI uses 3μg/kg
    • Other resources suggest 4μg/kg given an hour prior to the procedure

  • Supplemental oxygen should always be used; it should start on arrival in theatre and continue throughout
  • Ideally HFNO

  • The incidence of desaturation (SpO2 ≤90%) varies depending on oxygen techniques:
    • Low flow oxygen (<30L/min): 12 - 16%
    • High flow (30 - 70L/min), warmed and humidified oxygen: 0 - 1.5%

  • Effective topicalisation is required for successful ATI
  • No evidence that any one of the modes of topicalisation is superior to another:
    • Mucosal atomisation
    • 'Spray-as-you-go'
    • Transtracheal injection
    • Nebulisation
    • Glossopharyngeal and superior laryngeal nerve blocks (although higher LA toxicity and reduced patient comfort)
  • In view of this, each individual or institution may have its own 'recipe' e.g. the aforementioned Bristol recipe

  • However you choose to administer it, the maximum dose of lidocaine for airway topicalisation is 9mg/kg LBW (BJA, 2005) or 4.5mg/kg in paediatric patients

  • Following administration, atraumatically test the efficacy of topicalisation with a suction catheter, which both tests the bock and helps clear the airway
  • NB lidocaine wears off fairly quickly, so don't dally once the patient is topicalised

Nasal mucosa

  • Innervation: sphenopalatine ganglion via the maxillary (V2) division of the trigeminal nerve

  • Vasoconstriction is mandatory (Grade A evidence):
    • Xylometolazine
    • Co-phenylcaine i.e. 5mg/ml phenylephrine + 5% lidocaine
      • (Top tip: add otrivine (xylometolazine) to co-phenylcaine to increase vasoconstricting properties)
    • Moffat's solution (2ml 10% cocaine + 2ml 1% bicarbonate + 1ml 1:1000 adrenaline) is a theoretical option
      • Cocaine is not recommended as it is no more effective than co-phenylcaine but with a higher incidence of cardiovascular side effects
    • Adrenaline 1ml 1:1000 is another theoretical option

  • Local anaesthetic examples:
    • 2mls 2% lidocaine via mucosal atomisation device
    • Co-phenylcaine i.e. 5mg/ml phenylephrine + 5% lidocaine
    • 5mls 4% lidocaine via nebuliser
  • (Top tip: use a cotton swab stick to soak up any residual co-phenylcaine and use it to further topicalise the nasal passage of choice)

Tongue base & pharynx down to vallecular

  • Innervation: glossopharyngeal (IX) nerve

  • Local anaesthetic examples:
    • 10% lidocaine 0.1ml/spray via atomiser
    • 2% lidocaine via shaped atomiser device e.g. MADgic
  • (Top tip: ask the patient to gargle the local anaesthetic if possible)

Larynx above the vocal cords e.g. epiglottis, supraglottic mucous membranes

  • Innervation: superior laryngeal nerve, branch of vagus (X) nerve

  • Local anaesthetic examples:
    • 2% lidocaine via laryngotracheal atomiser device
    • 2% lidocaine 'spray as you go' via epidural catheter inserted into suction port of flexible bronchoscope

Larynx below the vocal cords (trans-tracheal)

  • Innervation: recurrent laryngeal nerve

  • 21 - 23G cannulae pierced through cricothyroid membrane
  • Aspiration of air to confirm tip of needle within trachea
  • Injection of lidocaine whilst patient exhales
  • Rapid removal of needle to ensure no trauma when the patient coughs

  • Benefits of leaving a wide-bore cannula in situ include:
    • Could be used for rescue oxygenation
    • Could be used as a conduit for a guidewire, facilitating Seldinger tracheostomy in cases of failed intubation or airway obstruction

  • ATI can be performed without sedation, however cautious sedation can be beneficial
  • It should be administered by an independent practitioner, to reduce the risk of over-sedation and its sequelae
  • Suggestions from DAS:
    • Single-agent strategy as it is safest
    • Remifentanil (or dexmedetomidine) as they are associated with high satisfaction and low risk of over-sedation/obstruction
    • Propofol is not recommended as there is greater risk of over-sedation, coughing and airway obstruction
Sedation options for ATI
No sedation
Remifentanil TCI Minto Ce 1-3ng/ml
Dexmedetomidine inf. 0.2-1μg/kg/hr
Midazolam 0.5-1mg bolus
Propofol TCI Marsh Ce 0.5-1μg/ml


  • Top tips
    • Lubricate the tube with spare 10% xylocaine, rather than optilube, as it tends not to be rubbed off as easily
    • Clean the tip of the scope with an alcohol steret prior to insertion
    • Lingering briefly at the nares rather than plunging straight in with the scope can help the patient become accommodated to having your hands and the scope near their face
    • If the scope tip gets muddied by secretions, optilube etc. then asking the patient to swallow can help clear the tip
    • A slow twizzling of the tube as you advance it (i.e. not necessarily corkscrewing; more gentle) can help find the correct orientation for easiest navigation

  • Patient movements:
    • Asking patient to protrude their tongue opens the oropharynx
    • Asking the patient to make an 'eeh' sound brings the epiglottis into view
    • Asking the patient to take a deep breath opens the glottis

  • Manage complications as below
  • Maximum 3 + 1 attempts

  • Only induce anaesthesia after a two-point check confirming ETT position; both visual and capnographic
  • Visual confirmation is of the ETT either through the vocal cords (VL) or in the trachea (FB)

Post-procedure

  • Document interventions as standard
  • Patients who underwent ATI due to predicted difficult airway are at high risk of complications at extubation, so your extubation strategy should be appropriately planned

  • Patients should be NBM for 2hrs post-topicalisation for ATI as lidocaine has a terminal elimination half-life of 2hrs

  • The overall rate of complication during ATI is quoted as 18%, though this encompasses a wide range of both minor and major complications

Minor complications

  • Sore throat (35%) - often resolves within 24-48hrs
  • Epistaxis (1.5 - 10%)
  • Nasal stuffiness (7%)
  • Dysphonia (5%)
  • 'Flu-like symptoms or cough (4%)
  • Feeling faint (2.5%)
  • Nausea or vomiting (1.5%)
  • Headache (3%) - a smaller percentage have a severe headahce (0.5%)

Issues with topicalisation

  • Pain / coughing / gagging may indicate a failure of topicalisation, and further LA up to the maximum dose can be applied
  • Topicalisation can cause laryngospasm
  • Local anaesthetic toxicity
    • In one study, 37% of participants experienced symptoms which may indicate early LAST
    • These included:
      • Light-headedness (14%) or dizziness (4%)
      • Drowsiness (5%), euphoria (3%) or dysphoria (5%)
      • Circumoral tingling (3%)
      • Paraesthesia (3%), some severe (0.5%)
      • Dysphagia (1%)

Issues with oxygenation

  • Hypoxia can occur, although less commonly with high-flow techniques
    • SpO2 <90% occurs in up to 1.5% according to DAS
    • SpO2 <80% occurred in 1.5% of those undergoing ATI in one study
  • Obstruction, inc. a 'cork in bottle' phenomenon caused by the 'scope/ETT
  • Hypoventilation

  • Management of oxygenation issues includes:
    • Clearing any airway obstruction
    • Increasing FiO2 or changing mode of oxygen delivery (e.g. HFNO if not already using)
    • Reducing or reversing sedation

Issues with sedation

  • Over-sedation should be managed by reducing sedation levels or reversing effects with reversal agents e.g. naloxone, flumazenil
  • Under-sedation should prompt review of the sedation regimen
  • Vomiting or aspiration

Cardiovascular complications

  • Increased BP ≥20% (23%)
  • Increased HR ≥20% (58%)
  • Dysrhythmia - often self-resolving e.g. nodal rhythm (3%)

Procedural complications

  • Multiple attempts at intubation; should follow DAS's 'failed ATI' algorithm if 3+1 unsuccessful attempts
  • Failed ATI i.e. other technique required
  • Airway trauma as with any airway instrumentation