The emerging role of awake videolaryngoscopy in airway management

Awake fibreoptic intubation has been considered the technique of choice when managing many types of predicted difficult airway. In principle, if a patient is maintaining the patency of their own airway, there is a margin of safety which is lost if general anaesthesia is induced before the trachea is intubated. Despite this, the Fourth National Audit Project of the Royal College of Anaesthetists (NAP4) reported that awake fibreoptic intubation was not used as the primary airway plan for many high-risk patients 1. However, awake fibreoptic intubation is a complex skill requiring regular practice to maintain competence. It is easy to see how this potentially difficult task, performed on a high-risk patient group, in departments where numbers of awake fibreoptic intubations may be low, may pose a problem; and in consequence, it is understandable that an anaesthetist might opt for a more familiar, but less appropriate, technique 1. It is of course also true that awake fibreoptic intubation is not suitable for tracheal intubation in all patients with airway problems, and it is not always successful; NAP4 demonstrated that it failed for a variety of reasons. Most commonly these were airway obstruction, lack of patient co-operation and difficulty recognising airway anatomy due to excess secretions, blood or suction failure 1. The NAP4 was published in 2011. However, anaesthetic practice is ever changing. In 2016, Ahmad and Bailey argued in this journal that awake fibreoptic intubation was becoming obsolete 2. Later that year, reviewing the revised Difficulty Airway Society's (DAS) guidelines on difficulties in intubation, Marshall and Pandit suggested that “if it is essential to maximise the first attempt success rate, and if it is the case that videolaryngoscopes yield higher success in visualising the glottis, then it follows that these should become first-line devices in most if not all tracheal intubations” 3. A Cochrane systematic review of videolaryngoscopy compared with direct laryngoscopy in adults concluded that “failed intubations were significantly fewer when videolaryngoscopy was used in participants with anticipated difficult airway.” 4, although a similar review found no evidence of benefit in children 5. In addition to this, the recent DAS guidelines on intubation in critically ill adults acknowledge the role of videolaryngoscopy 6, stating that “if difficult laryngoscopy is predicted then videolaryngoscopy should be considered from the outset”. However, these publications deal largely with the management of intubation in patients who are anaesthetised. This month's issue of Anaesthesia presents a systematic review comparing awake videolaryngoscopy and awake fibreoptic intubation in patients with anticipated airway difficulty 7. Using standard systematic review methodology, the authors included eight studies overall. One study could not be included in the quantitative meta-analysis, leaving data from 408 patients in the remaining seven trials for the primary outcome, which was the time taken to intubate the trachea 8. These numbers are small, and no trial sequential analysis was performed to establish whether a sufficient number of patients were present to be confident about the findings 9. Nevertheless, the results appear to show that awake videolaryngoscopy reduces the time to achieve intubation, and otherwise the techniques are broadly comparable. Understanding the details of the techniques used is vital not only in making sense of the systematic review, but equally in translating the review's findings into clinical practice. All studies used a remifentanil infusion with or without midazolam boluses as sedation for both awake videolaryngoscopy and awake fibreoptic intubation, except for the earliest study which used fentanyl and midazolam. Where recorded, a Ramsay sedation score of 2–3 was targeted. This raises the question how ‘awake’ patients undergoing these procedures truly are. The Ramsay sedation score describes a patient's response to sedation as a continuum: from level 1 where the patient is alert, anxious and agitated; to level 6, where the patient is unresponsive. It defines levels 1–3 as ‘awake’ and 4–6 as ‘asleep’ 10. This binary awake/asleep description is simple, but deeper sedation may reduce the safety margin offered by nominally ‘awake’ techniques. It is also important to note that very high levels of anxiety can also increase risk due to the physiological response to stress and the potential reduction in patient compliance during airway management. This concept of a theoretical target for an ‘awake’ patient (i.e. effective anxiolysis while the patient remains alert to their surroundings) perhaps highlights the benefits that target-controlled remifentanil infusions have provided in the management of these patients. All studies used topical lidocaine on the airway, adopting a range of techniques including: transtracheal injection 11; nebulised lidocaine 12; ‘spray as you go’ metered lidocaine spray 13 and the ‘Mackenzie technique’ 14. In this, lidocaine is injected into the side port of a standard intravenous cannula, directed into the airway through the mouth and connected to a supply of oxygen which then deposits the drug on the mucosa of the airway. Given the variety of such techniques, the number of different types of videolaryngoscopes used and the types of patients included in the studies, it is no surprise that a high level of heterogeneity was present in the meta-analysis 15. In response to this, the authors downgraded their assessment of the quality of evidence for the primary outcome. As mentioned above, the patient's experience must always be considered when an ‘awake’ airway management technique is used. When recorded, studies in the review that examined patient satisfaction found both techniques to be equally well received, with most patients rating their experiences as excellent 13, and hypothetically agreeing to the same technique should they need awake intubation again 16. In addition, although the primary studies were not powered to detect a difference in complications, there were no major problems. Levels of failed intubation, nasopharyngeal bleeding, sore throat, hoarseness and minor respiratory/cardiovascular compromise were rare in both groups and, perhaps predictably, not significantly different between them. Again, the details of technique – not simply what is done, but how it is done – are important in reducing complications. Thus, awake videolaryngoscopy seems to be probably faster, and at least as safe, as awake fibreoptic bronchoscopy. The ‘big screen’ offered by awake videolaryngoscopy allows improved spatial awareness and a larger field of view, aiding the recognition of airway anatomy and direct observation of actions in the airway, such as application of local anaesthetic and suction. It avoids the ‘red out’ phenomenon which can occur with the fibrescope, where the tip of the fibrescope is pressed against tissue or debris in the airway. It also allows the passage of the tracheal tube through the vocal cords to be observed externally, which may be an advantage as this may be a ‘sticking point’ even when the fibrescope itself has been successfully passed through the cords. The upper airway can be examined after tube placement, which can be helpful in cases where the risk of bleeding is high, such as when there is a tumour in the upper airway. The presence of a fibrescope within the tracheal tube can also cause the ‘cork in the bottle’ effect sometimes seen in awake fibreoptic intubation. The sudden increase in impedance to air flow as the tube passes the vocal cords can cause dyspnoea and anxiety. Again, this is not a problem with awake videolaryngoscopy. Related to this is the ability to select different diameters of tracheal tube with awake videolaryngoscopy, especially useful when a narrow microlaryngoscopy tube is needed. Finally, gentle traction with the videolaryngoscope can create more space in the airway; this can be useful when an obstructing lesion is present, or when obesity compresses airway structures. Of course, no single airway management technique can be used for every patient. Videolaryngoscopy cannot be used when mouth opening is limited, and as such these patients were not included in the studies in the review by Alhomary et al. 7. In these cases, awake nasal fibreoptic intubation is still essential. However, awake videolaryngoscopy would be entirely appropriate in patients who were difficult to mask ventilate 17 and in the obese, as complications are frequent in those with a higher body mass index 18. Indeed, one of the studies included in Alhomary et al.'s review included only obese patients 13. It is still unclear what role awake videolaryngoscopy has in the management of suspected cervical spine injuries. One of the studies reviewed patients receiving elective cervical spine fixation, although the airway difficulty created by cervical immobilisation in patients with an acute spine injury might not be quite the same 12. The DAS is currently preparing guidance on the use of awake airway management techniques which we expect will be helpful in further defining the role of awake videolaryngoscopy. Anaesthetists, and in particular those in training, are finding videolaryngoscopy techniques of all kinds becoming more prevalent in their practice 19. The benefits of videolaryngoscopy seem to be apparent when used by expert anaesthetists 20, but even medical students can be instructed in their use 21. With higher levels of exposure and increasing use of videolaryngoscopy, one can see how this can inspire us to adopt these techniques in ‘awake’ patients. However, the adoption of a novel technique which is potentially easier to master poses an obvious counterpoint. Fibreoptic intubation is already underused and there is the danger that the greater use of awake videolaryngoscopy further erodes clinicians’ confidence and experience with awake fibreoptic intubation. Thus, although for most patients requiring awake intubation awake videolaryngoscopy might come to offer a more familiar technique, it potentially further mystifies awake fibreoptic intubation and makes it even more of a rarity. Will this put patients for whom awake fibreoptic intubation is the only choice for airway management at risk? This utilitarian issue of changing practice for the greater good, while leaving a smaller number of patients potentially disadvantaged, poses an ethical conundrum. One should, however, be careful not to polarise the argument and suggest that the two techniques are mutually exclusive. They are not; they both have their uses, and in fact can be used, if necessary, simultaneously in the same patient to optimise both oropharyngeal view and guided tube placement. There are a number of unanswered questions about the role of awake videolaryngoscopy in airway management. Could it be used instead of rapid sequence induction in the non-fasted patient? Topical anaesthesia to the airway seems to be safe during awake fibreoptic intubation and the same should hold for awake videolaryngoscopy, although it would still be possible to apply cricoid pressure if this were thought necessary. In patients with cardiovascular disease, expert topical airway anaesthesia and videolaryngoscopic intubation should, in principle, avoid the need for an unpredictable drop in arterial pressure with the induction agent and a similarly undesirable rise in pressure and heart rate on tracheal intubation. As mentioned previously, would awake videolaryngoscopy be appropriate for patients in the Emergency Department, especially those with cervical spine injury? Further research is definitely required to resolve these questions. What, then, are the implications for airway management policy and training? Although NAP4 recommended that: “all anaesthetic departments should provide a service where the skills and equipment are available to deliver awake fibreoptic intubation whenever it is indicated” 1, Marshall and Chrimes have “challenged the assumption that all anaesthetists need to possess the full range of technical skills for airway management”, suggesting instead that most anaesthetists should instead develop a “more limited repertoire of “core” techniques” 22. Although tracheal intubation is, of course, one of these techniques, they did not specify whether videolaryngoscopy might be used. Our personal opinion is that awake videolaryngoscopy should be a ‘core’ technique, and in fact we would go further and reiterate the previously expressed view that awake intubation using a videolaryngoscope should be a primary technique for novice anaesthetists 23. AFS is an Editor of Anaesthesia. No other competing interests declared.