From variance to guidance for awake tracheal intubation

Awake tracheal intubation remains the gold standard for difficult airway management. Since the advent of the flexible fibreoptic endoscope, anaesthetists have learned to use this technique to safely secure tracheal tubes and avoid critical respiratory events. Newer modalities for asleep airway management such as videolaryngoscopes and supraglottic airway devices have further advanced safe airway management but have not replaced awake tracheal intubation. Since the 1980s, we have learned to perform this technique from those that taught us or from airway management courses. However, there has been no guidance from airway management guidelines on how this critical technique should be performed. In this issue of Anaesthesia, Ahmad et al., representing the Difficult Airway Society, offer much needed guidelines for this approach 1. The authors came to this guidance via a robust process. They followed recommended standards for conducting systematic reviews. In doing so, they evaluated the existing evidence and appropriately graded each recommendation based on the strength of that evidence. They met multiple times and utilised the Delphi technique to bring value and uniformity to each recommendation. Uniquely, they also engaged patients for input. This engagement is something often absent from anaesthetic guidance but vitally important to this procedure because the patient experience during awake tracheal intubation cannot be undervalued. Certainly, patients also want the safest approach to airway management, but no patient appreciates discomfort. Recognising this important patient perspective adds value to these recommendations. The most notable feature of these guidelines is the relative absence of the highest level evidence behind each recommendation. Although some guidance is supported by grade-A evidence from randomised trials, many of the recommendations are simply supported by the opinions of these experts (grade D). These guidelines stand in contrast to many other clinical care guidelines that are only formulated once the strength of evidence is so compelling that there is an urgent need to standardise care. These findings highlight that these guidelines should not represent standard care for every clinician, but rather a consideration for those unfamiliar with how to approach a step during awake tracheal intubation. So, why should we offer any guidance at all when the evidence is limited or non-existent? Certainly, many providers have learned to perform this technique and do not need these guidelines to safely care for their patients. However, standardised care does support patient safety. Adherence to clinical practice guidelines is associated with reduced mortality, reduced cost of care and hospitalisation when studied for cancer, cardiovascular or respiratory care 2-5. Bringing uniformity to a clinical approach that carries patient risk offers the advantage of making each step and subsequent outcome predictable. When the entire clinical care team has a robust understanding of equipment needs, set up and procedural steps, the most efficient help is offered as it is familiar to all. These team members are also more likely to identify abnormalities because we can clearly identify what is 'normal' when we standardise care. So, despite some limited evidence basis, we argue that the mere presence of guidelines for care supports patient safety and helps the infrequent user. Beyond safety and efficiency, standardised care offers another important advantage. It serves to advance the science of the care we provide. When we all approach awake tracheal intubation differently, we have limited understanding of what works and how we may improve. Instead, we have all heard things like, 'This is how I do it, and it works well'. We have no idea if that approach is what works, the providers' familiarity with their own approach or the individual provider's skill set and bed-side manner. With these guidelines, we now effectively have a control by which we can conduct clinical experiments. Defining this usual care serves future investigators' capacity to advance the science of awake tracheal intubation. Clinicians may find relief in the only controlled study on the patient's experience of the procedure 6. In the awake group, patients lightly sedated to a Ramsay sedation scale of 2 (co-operative, orientated and tranquil) or 3 (responding to commands only), only one in seven patients reported any discomfort. When the patients were asked what they feared the most (if they feared anything), almost twice as many (27%) answered that they feared the surgery compared with tracheal intubation (17%) 6. Procedural time may be trivial if the clinician becomes proficient with the procedure. The median time to perform awake tracheal intubation is only 8 min longer than for tracheal intubation after induction 7. However, time itself should not be the determining factor in cases where awake tracheal intubation is considered the safest approach, and the alternative, tracheal intubation attempt after induction of anaesthesia in a predicted difficult airway patient may well take longer, and bears the concomitant increased risk of having to revert to emergency front-of-neck access. These guidelines do not include detailed recommendations on which patient features or conditions merit awake tracheal intubation. Historically, bed-side examination features indicating a difficult direct laryngoscopy, such as a high Mallampati classification score, were common indications for awake tracheal intubation, but evidence suggests that asleep videolaryngoscopy may often overcome this barrier 8. One may suspect that this advancement has resulted in a reduction in the incidence of awake tracheal intubations performed, but these presumptions have not been supported by evidence to date 9. We opine that certain patient populations deserve routine consideration for awake tracheal intubation. First, the patient with neck pathology from tumour, previous surgery, obstructive lesions or radiation therapy is known to be at increased risk for failed facemask ventilation, direct laryngoscopy, videolaryngoscopy and potentially surgical airway 10, 11. It seems prudent to consider the nature of the pathology in these patients and come to a reassurance that asleep airway management is safe before induction of anaesthesia, and if not, then choose awake tracheal intubation. We also suggest that there may be haemodynamic indications for awake tracheal intubation: once the airway is secured it allows a gradual transition to positive pressure ventilation and a slow induction of anaesthesia for those who may suffer from increased risk of haemodynamic collapse. The patient with a large anterior mediastinal mass may meet such an indication. Further considerations are summarised in Table 1. The reader might get the impression from these guidelines that only two techniques exist for awake tracheal intubation: flexible bronchoscopy (FB) and videolaryngoscopy (VL) with brief mentioning of awake tracheal intubation via a supraglottic airway or guided by a lighted stylet. We highlight that grade-A evidence supporting comparable success rates of awake intubation with VL with FB are limited by study design to patient cohorts with relatively easy oral access who are often deeply sedated. We agree that awake tracheal intubation with FB and VL will cover the vast majority of situations, but these techniques are not equally applicable, and in many patients, awake VL will be difficult, or even impossible (e.g. insufficient mouth opening). We think that it is essential for anaesthetists to realise that all tracheal intubation techniques can be applied in the awake patient. The authors state that bleeding is a relative contra-indication for awake tracheal intubation – we strongly disagree! Yes, awake tracheal intubation with FB or VL may be difficult, or impossible, in the bleeding patient, but if the airway examination indicates an anatomically difficult airway then an awake approach, either awake tracheal intubation or awake front-of-neck access, is definitively as indicated as it would have been had the airway not been bleeding – or even more so 13. Awake tracheal intubation can still be achieved, even if severe bleeding impedes visibility with VL and FB, by using techniques that are relatively unaffected by the presence of blood 12. These techniques include retrograde-12, blind nasal-, light- or flexible-video/optical scope-guided tracheal intubation via a supraglottic airway device (provided the origin of the bleeding is above the supraglottic airway device); or awake front-of-neck access 12. Awake front-of-neck access remains the most conservative approach to difficult airway management and should always be considered. The authors state that there is no proven benefit of the oral or nasal route; however, it is obvious that some potentially severe complications as epistaxis can only happen if the nasal route is chosen. We thus suggest the oral route to be chosen as the first choice, all other indications being equal. The authors have given in to the understandable temptation to use a well-sounding acronym 'sTOP' to highlight the steps for awake tracheal intubation, but we believe that it can be misleading. Here 'sTOP' stands for 'sedation, topicalisation, oxygenation and performance' and may prompt the clinician to perform the tasks in that sequence which could become dangerous because both sedation and topicalisation can cause apnoea and obstruction and thus must be preceded and accompanied by distribution of oxygen. Furthermore, sedation, if to be used at all, should come before topicalisation because topicalisation may be equally uncomfortable for the patient as tracheal intubation itself, and therefore should be preceded by sedation. So, from a clinical point of view, and as a help for the infrequent user, the sequence should be: 'oxygenation, sedation, topicalisation and performance' (OsTP). However, as it has been shown that abbreviations 14 and acronyms 15 in medicine and science are often counterproductive and may present an imminent disaster 14, we suggest using words spelt out in full. Additionally, this would also prevent confusion with the use of the word 'sTOP' in the 'unsuccessful awake tracheal intubation' part of the guidelines, where it actually means stop! The guidelines define an unsuccessful attempt at awake tracheal intubation as "unplanned removal of flexible bronchoscope, videolaryngoscope or tracheal tube from the airway". The guidelines state that if a total of three to four attempts at awake tracheal intubation have failed and if abandoning tracheal intubation is not an option and awake front-of-neck access is inappropriate or unsuccessful then 'the only remaining option is a high-risk anaesthetic' involving induction of anaesthesia despite the prediction of the considerable likelihood of failure. We do not agree that a 'high-risk anaesthetic' is the only option. Following the definition above, withdrawal of the flexible scope due to secretions four times would prompt the team to abandon awake tracheal intubation. If the attempts have been gentle and atraumatic then additional optimised attempts by an alternative technique/operator/sedation can still be the answer and may very well be safer than the risky induction of anaesthesia with apnoea. Furthermore, there is an additional option in this scenario: deep sedation or general anaesthesia with preserved spontaneous ventilation which bears several advantages over managing the difficult airway of an apnoeic patient (see Table 1). In this setting, induction and maintenance with ketamine 16 can be favourable. If the 'high-risk anaesthetic' is chosen, then this should only occur after the trachea and the cricothyroid membrane are identified and properly marked, if necessary with the aid of ultrasonography 17. With the advent of simulators that can simulate both pathology in the airway and the patients' reaction to tracheal intubation attempts, it is now possible to train for awake tracheal intubation even in the absence of patients whose airways are difficult to manage. Training with these simulators has been shown to improve tracheal intubation success (at least in anaesthetised patients 18). These simulators have proven their validity 19 and we encourage their incorporation into training programmes for residents and for achievement and maintenance of skills for anaesthetists. New adjuncts, like an emitter of infrared blinking light placed on the skin on the cricothyroid membrane, resulting in visible light emerging from the trachea as guidance for the flexible scope 20, may further support the safe application of awake intubation for the infrequent user. This editorial is intended to help get the most out of these guidelines with their impressive attention to detail and clinical usefulness. We encourage all airway practitioners, both novice and expert, to scrutinise and use these guidelines for improvement of personal readiness and capability to perform awake tracheal intubation. We further encourage regional and departmental standards based on these guidelines and commentary. No competing interests declared.