Newsletter June 2021: Clinical corner - The quest for a smooth extubation!

Marcelo Sperandio Ramos
marcelosperandioramos@yahoo.com

Clinical corner – The quest for smooth extubation! – I banned air from the ETT cuff for good…

It is known for a fact that tracheal extubation is associated with a significant risk of complications, – The Difficult Airway Society (DAS) developed a guideline for the management of tracheal extubation in 2012. While the DAS guideline provides an excellent starting point in developing strategies for achieving successful extubation, it does not provide a distinction between successful extubation and smooth extubation. The concept of smooth emergence was mentioned in the DAS guideline as desirable for the success of certain surgical procedures, but it did not specify which procedures. Despite much of the discussion regarding extubation techniques in the literature, there is no precise definition of “smooth extubation”. Coughing during emergence from general anaesthesia affects 40 to76% of intubated patients. Among the physiological sequelae of peri-extubation coughing, we can cite complications as neck haematoma after thyroidectomy or carotid endarterectomy, wound dehiscence after laparotomy, and intracerebral haemorrhage after intracranial surgery. As such, the ”quest for a smooth extubation” has been pursued in the literature, as I do so in my practice. Multiple medications have been shown to reduce emergence coughing in isolation, such as lidocaine (I.V., intracuff, topical, and tracheal routes), dexmedetomidine, fentanyl, and remifentanil. Beyond the humanitarian aspect the ”smooth extubation” should be a goal to be pursued even in ordinary anaesthesia, because it is a potentially avoidable source of complications for any patient. It is uncertain; however, which combination of measures and/or medication is the most effective for reducing this adverse event. Studies are limited by small sample sizes and heterogenous medication dosages. These limitations are also reflected in the published systematic reviews and meta-analyses. , . Importantly, studies are sparse with a meaningful head-to-head comparison of medications. As such, the comparative effects of these medications to reduce perioperative cough are unknown.

It should be noted that the COVID-19 pandemic has heightened the importance of developing our knowledge of effective techniques to achieve smooth emergence. In an effort to reduce the transmission of COVID-19 to healthcare workers, smooth extubation may contribute to primary prevention by reducing coughing, bucking, and aerosolisation.

Among methods used to apply a local anaesthetic to the mucosa, intracuff lidocaine, in addition to the local anaesthetic effect and suppressing complications during extubation, prevents diffusion of nitrous oxide into the ETT cuff without delaying awakening. Coughing during emergence from general anaesthesia is a common clinical problem. Inflation of the endotracheal tube cuff with lidocaine would create a reservoir of local anaesthetic, which might diffuse across the cuff membrane to anaesthetize the mucosa and attenuate tracheal stimulation. Lidocaine efficacy has long been known since was evaluated in a Cochrane review in 2009. Lidocaine administered as a cuff inflation medium reduces sensitive input from the tracheal mucosa through its continuous topical anaesthetic effect. Alkalinised lidocaine could have a potential advantage over its non-alkalinised variety, with a quicker onset, duration, and quality of the block, despite the possibility of completely losing its anaesthetic action due to precipitation if a minimal error in the addition of bicarbonate occurs.

By filling the cuff with lidocaine, diffusion of the uncharged base form of the drug occurred across the hydrophobic PVC walls of the ETT cuff. Lidocaine binds avidly to the respiratory mucosa, where it exerts its action blocking the sensitive input from the tracheal mucosa. The absorption characteristics of the mucosa, epithelial thickness, number of membrane pores and tissue pH also serve to delay absorption. Thus, the tracheal mucosa in direct contact with the ETT cuff wall can be anaesthetised locally with a longer than expected effect of lidocaine and with intact supraglottic reflexes, preventing aspiration in these patients even though buffered lidocaine could achieve better results – even plain 2% lidocaine injected into the ETT cuff, not only reducing the incidence of a sore throat but also enables improved ETT tolerance and helps in producing smooth extubation in patients with hyperactive airways.

Based on all the mentioned literature and my observation during my clinical practice, I switched room air for lidocaine into the cuff since 2000, and since then I have been employing lidocaine for filling the cuffs for good.

References

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