"At-risk extubation" defines a situation where there is some uncertainty as to whether or not the patient will stay extubated for any prolonged period of time. This state is characterised by the expectation of difficult reintubation or by the presence of incompletely met criteria for extubation, be it a full stomach, haemodynamic instablily, poor neurological performance or metabolic derangement.
"Difficult extubation" has no formal definition as such. Cavallone et al (2013) are the authors of the most sensibles-sounding article on this topic, and even they were unable to define it beyond using specific examples. It seems to be the inverse of difficult intubation, i.e. there is some sort of crude mechanical barrier to getting the tube out. In lay terms, the tube is stuck. This is weird and rare. Historically, case reports have included accidental stitching of the ETT into the trachea, transfixation of the ETT by a skeletal traction wire, failure of the cuff to deflate, formation of barbs along a lacerated tube, and the total disappearance of a shortened ETT into the depths of the patient's airway. Lang et al (1989) chronicle these and numerous other hilarious tracheal tube mishaps, completing the collection with the first case report of a nasotracheal tube being permanently affixed to the patient with a Luhr plate screw.
Both Question 11 from the second paper of 2011 and Question 2a from the second paper of 2004 asked the candidates to assess for extubation a 45 year old "intellectually handicapped man" who was intubated for the evacuation of an airway-obstructing dental abscess. Similarly, Question 26 from the second paper of 2020 presented the candidates with a borderline-awake cardiac arrest survivor. This sort of question takes emphasis away from normal ventilator weaning, but on the preparation for extubation failure, and for the possibility that reintubation will be difficult.
A good literature resource to answer these sorts of SAQs is the "Difficult Airway Society Guidelines for the management of tracheal extubation" ( Mitchell et al, 2012). This statement has informed most of the ensuing summary. The time-poor candidate could safely limit their reading to Lang et al (2013), who have published an excellent review of at-risk extubation and extubation failure.
Why do we make such a big deal of this reversible airway manipulation?
The normal criteria for extubation readiness are outlined below.
Basic pre-conditions |
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Airway protection assessment |
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Gas exchange criteria |
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Lung mechanics criteria |
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The extubation criteria are not carved in stone. On occasion, one may be tempted to extubate what might be described as a "borderline" patient, who may not be a hundred percent cooperative, or who may have impaired airway reflexes, or whose disease state may not have completely resolved.
In short, there are situations where intensivist has made the extubation difficult by virtue of their impatience.
In addition, the airway may be difficult, thus making this a "difficult re-intubation". The Difficult Airway Society propose the following problem domains to describe such an "at-risk" extubation:
One might view the following as an "extended" list of extubation criteria, specificaly relevant to the situation where one is concerned about post-extubation airway patency, and where one is not confident in one's ability to reintubate the patient in a hurry. A classical example is the head-and-neck radiotherapy patient who gets intubated for an elective occipitocervical spinal fusion, and is then discovered to have a rip-roaring dental infection which they failed to mention at the pre-admission clinic.
There are a few strange bedside tests and investigations which may be considered in specific circumstances, but which do not form a part of even the "extended" list of pre-extubation assessments. These were largely scraped together from Table 3 in the 2013 article by Lang et al.
Karmarkar, Swati, and Seema Varshney. "Tracheal extubation." Continuing Education in Anaesthesia, Critical Care & Pain 8.6 (2008): 214-220.
Mitchell, V., et al. "Difficult Airway Society Guidelines for the management of tracheal extubation." Anaesthesia 67.3 (2012): 318-340.
Kriner, Eric J., Shirin Shafazand, and Gene L. Colice. "The endotracheal tube cuff-leak test as a predictor for postextubation stridor." Respiratory care 50.12 (2005): 1632-1638.
Loudermilk, Eric P., et al. "A prospective study of the safety of tracheal extubation using a pediatric airway exchange catheter for patients with a known difficult airway." CHEST Journal 111.6 (1997): 1660-1665.
Sorbello, M., and G. Frova. "When the end is really the end? The extubation in the difficult airway patient." Minerva anestesiologica 79.2 (2013): 194-199.
Cavallone, Laura F., and Andrea Vannucci. "Extubation of the difficult airway and extubation failure." Anesthesia & Analgesia 116.2 (2013): 368-383.
LEE, CHINGMUH, SANDY SCHWARTZ, and MARTIN S. MOK. "Difficult extubation due to transfixation of a nasotracheal tube by a Kirschner wire." The Journal of the American Society of Anesthesiologists 46.6 (1977): 424-424.
Lang, Scott, et al. "Difficult tracheal extubation." Canadian Journal of Anaesthesia 36.3 (1989): 340-342.
Ding, L. W., et al. "Laryngeal ultrasound: a useful method in predicting post-extubation stridor. A pilot study." European Respiratory Journal 27.2 (2006): 384-389.