Awake Fiberoptic Intubation in the ICU

Created on Sun, 06/12/2016 - 07:47
Last updated on Tue, 06/28/2016 - 03:12

AFI is the gold standard of management for the difficult airway, and is found at the end of most algorithms which describe elective difficult intubation. Along with awake laryngscopy, this techniqye avoids the drama of an anaesthetic, with the patient remaining awake and breathing spontaneously up until their airway gets a cuffed tube into it. Its major disadvantages are the need for fiddly preparation, the reliance on patient cooperation and the risk of vomiting and aspiration with an insufficiently topicalised airway.

Question 13 from the first paper of 2016 and the identical Question 21 from the first paper of 2011 were the only questions to ever discuss AFI. It posed a situation where a hypoxic patient with ankylosing spondylitis requires a semi-elective awake fiberoptic intubation. This question separated the dual trainees in ICU and anaesthetics from those who don't routinely have their hands on an intubating bronchoscope. The college model answer to this question was actually quite good, and was reinterpreted into the Discussion section with minimal modification (only verbal pruning).

As far as publications go, one cannot go past the excellent LITFL page on this topic, which features hilarious videous (including one of Michael Bailin intubating himself). For most people this is enough. For those who instead wish to submerge into detail, Stephen Collins has written an excellent free article (Respiratory Care, 2014) which extends all the way to a discussion of bronchoscope engineering and the development of bronchoscopic technology. Practical details for airway topicalisation and bronchoscope steering can be found at frca.co.uk.

Rationale for awake fiberoptic intubation

Why would you want to do this? Specifically, why do the various international societies recommend this procedure as the "gold standard" of difficult airway management? Well.

  • Mortallity in difficult airway management occurs when the patient is anaesthetised, stops breathing, and no avenue of ventilation is available.
  • The failure and "loss" of the airway during intubation occurs when the anaesthetised patient cannot be intubated because the vocal cords cannot be visualised.
  • Thus, if one remains awake and breathing spontaneously during the intubation, one should not become hypoxic from apnoea.
  • Similarly, the use of a  fiberoptic bronchoscope to intubate insures that the cords can be visualised and the trachea reliably intubated.
  • The flexible fiberoptic bronchoscope is the best-tolerated vehicle for intubation because it is narrow and flexible, offering more patient comfort than other options.
  • It also offers the opportunity to visually inspect the airway anatomy, which could be useful if there has been burns, airway trauma, inhalational injury, caustic ingestion, etc.
  • Airway reflexes may be blunted with local anaesthetic, or they can be left as they are to reduce the risk of aspiration 

Videolaryngoscopy as an alternative

One may also use the same rationale to justify awake videolaryngoscopy. Rosenstock et al randomly allocated 93 adult difficult airway patients to be intubated either with a flexible bronchoscope or using the McGrath videolaryngoscope. For the AFI, first-attempt success rate was 79%, versus 71% for the McGrath. However, the McGrath group got their tubes in faster (at a median time of 62 seconds, instead of 80 seconds with the bronchoscope). Weirdly, one patient could not be intubated with the AFI and was successfulyl intubated with the McGrath (wait, which  was the gold standard again?). Of course, all of these patients were reasonably healthy elective outpatients. The authors concluded that ultimately there is no difference between techniques, or at least if there is such a difference then their study was underpowered to find it (to detect an 8% difference in intubation success with 80% power they would have needed n=1000).

Indications for awake fiberoptic intubation

The following indications are composed of widely held beliefs and non-factual expert opinion. However, they make some sense. Here, they have been categorised according to which part of conventional intubation is made impossible by the patient factors.

Cannot move the C-spine

  • Ankylosing spondylitis
  • Unstable C-spine fracture
  • Fusion of C-spine vertebra, eg. Pierre Robin syndrome (or surgical fusion) 

Cannot open mouth wide enough for the laryngoscope blade

  • Mandible fracture
  • Congenital abnormality
  • Submandibular infection, eg. abscess

Airway anatomy is very abnormal

  • Macroglossia
  • Head and neck cancers
  • Airway-involving injuries

Should not / cannot lie down to be intubated

  • Severe orthopnoea
  • Morbid obesity

Cricothyroidotomy is not an option

  • Morbidly obese, short neck
  • Abnormal anatomy (weird larynx)
  • Infected anterior neck

Risk and logistics do not favour other techniques

  • History of difficult direct laryngoscopy (for whatever reason)
  • No videolaryngoscope available
  • Patient meets various predictive criteria for difficult intubation

Relative contraindications for awake fiberoptic intubation

  • Severe airway infection:  A closed claims analysis of AFI fuckups had identified 12 claims with a mortality rate of 75%. Upper airway obstruction developed after minimal sedation or airway instrumentation, and resulted in death. Of these cases, the majority were associated with some sort of airway abscess.
  • Operator ineptitude: you need to do these regularly to remember how to do it, otherwise one may develop lifethreatening complications.
  • High risk of vomiting and aspiration: even though you topicalise, there is a chance of aspiration; and the topical agents are usually nauseatingly foul-tasting.
  • Fractured base of skull (nasal AFI is contraindicated)
  • Impending airway failure - AFI takes too long to prepare, and the patient will be dead without immediate action. In this category one might also place the patient experiencing a cardiac arrest.
  • Grossly contaminated airway will make mockery of bronchoscopy, as filth gets caked on to the bronchoscope lens.
  • Allergy to local anaesthetic agents without which the AFI is essentially impossible.

A brief checklist of preparatory steps

  • Preparation of equipment
    • bronchoscope is cleaned and checked
    • monitoring equipment is attached
    • Plan B equipment is at the ready (eg. cricothyroidotomy kit)
    • drugs are ready, including local anaesthetics, general anaesthetics, sedatives, opiates, muscle relaxant
  • Preparation of staff
    • skilled staff are available, and briefed about the procedure
    • backup is available, in the form of a senior anaesthetist
  • Preparation of patient
    • get consent
    • explain procedure
    • position the patient comfortably
    • administer mild sedative (eg. small dose of midazolam)
  • Preparation of airway
    • administer glycopyrrolate or atropine to dry secretions
    • spray 10% lignocaine with phenylephrine using atomiser

A technique for awake oral fiberoptic intubation

  • Position the patient: supine if they can, seated if they cannot.
  • For oral intubation, a suitable airway introducer is used. 4 nebulised puffs of 10% lignocaine/phenylephrine spray are administered to the throat (2 each side, tonsillar pillows and back of throat) totalling 40mg of lignocaine.
  • Use the directed nozzle to spray more atomised lignocaine into the posterior pharynx
  • Alternatives include using a "spray as you go" approach through the bronchoscope, or using transtracheal injection of lignocaine (into the cricothyroid membrane) which gets spread around by the resulting cough.
  • Once the airway is well topicalised, load the ETT on to the bronchoscope
  • Advance the bronchoscope to the mid-trachea
  • Advance the well-lubricated ETT over the bronchoscope, using a gentle rotating motion. Watch the carina the whole time, to prevent dislocation of the bronchoscope tip out of the trachea.

 

References

Walsh, Mary E., and G. D. Shorten. "Preparing to perform an awake fiberoptic intubation." The Yale journal of biology and medicine 71.6 (1998): 537.

Rosenstock, Charlotte V., et al. "Awake Fiberoptic or Awake Video Laryngoscopic Tracheal Intubation in Patients with Anticipated Difficult Airway ManagementA Randomized Clinical Trial." The Journal of the American Society of Anesthesiologists 116.6 (2012): 1210-1216.

Leslie, David, and Mark Stacey. "Awake intubation." Continuing Education in Anaesthesia, Critical Care & Pain (2014): mku015.

Peterson, Gene N., et al. "Management of the Difficult AirwayA Closed Claims Analysis." The Journal of the American Society of Anesthesiologists 103.1 (2005): 33-39.

Ramkumar, Venkateswaran. "Preparation of the patient and the airway for awake intubation." Indian journal of anaesthesia 55.5 (2011): 442.

Collins, Stephen R., and Randal S. Blank. "Fiberoptic intubation: an overview and update." Respiratory care 59.6 (2014): 865-880.