The case against preoperative endoscopic airway examination (PEAE) in the “ENT airway”

Airway management in anesthesiology continues to be the focus of much research, discussion, and development. It is considered one of the pillars, if not the major pillar, of what anesthesiologists do in the operating rooms and beyond. Awake intubation is a commonly used term to describe an endotracheal intubation while the patient is sedated and spontaneously breathing and the airway is tropicalized. This approach to the potential/anticipated and known difficult or critical airway1, has been developed and used successfully for decades. It is more frequently used in head and neck surgeries (the so called “The ENT Airway”) when airway anatomical derangements are encountered. These derangements could be due to either tumors, and/or as consequences to prior surgical (eg, resection and/or reconstruction) and/or therapeutic (eg, radiation) interventions. Anesthesiologists who are specialized in this field have known for years that the ENT airway should be managed with caution and “respect”. Forty percent of cases reported to the NAP4 project (4th National Audit Project in the United Kingdom that collected data on patients who suffered airway related complications in 2010) were head and neck surgery patients2. This is not at all surprising for obvious reasons related to the nature of the pathologies that these surgeries address and, regretfully, the new advances in airway management in the last 2 decades have not dramatically eased the ENT airway challenge. Specifically, videolaryngoscopes are known to fail on occasion, and among the cited reasons for failure are some of the frequently encountered pathologies in the head and neck field; neck radiation, airway masses, and prior flap reconstruction3. Moreover, neck masses and/or radiation are among the predictors of failed mask ventilation identified in a large database study4. In this issue McAvoy and colleagues5 described a case report in which the authors utilized a Preoperative Endoscopic Airway Examination (PEAE) to determine whether the patient’s airway was to be managed by postinduction (asleep) intubation versus awake intubation. While the report is well written, and the PEAE approach in general is unique and innovative, it is not without controversy and merits some contrarian discussion, which I will provide next. It is claimed that utilizing PEAE provides more valuable information than static computed tomography scan (CT) images, as it provides dynamic images of the airway6. Indeed static images cannot with certainty predict what the airway would look like before or after induction. Likewise, the PEAE findings in an awake spontaneously breathing patients and probably sitting upright, cannot predict what the airway would look like after induction of anesthesia in the supine position. Moreover, the criteria derived from PEAE findings based on which a decision to proceed with awake or asleep intubation are not yet evidence-based, or validated and so are prone to individual interpretation. Thus, it remains unknown whether the PEAE findings that are considered or thought of as being suggestive of an easy intubation are indeed predictive of the same after the induction of anesthesia. PEAE is meant to avoid “unnecessary awake intubations”6 proponents of this technique consider that as a favorable outcome and a huge advantage due to the alleged discomfort and suffering that the patient encounters during awake intubation. Such concerns certainly have some merit in inexperienced hands versus when performed properly by well trained and experienced anesthesiologists; however that does not mean that we should abandon awake intubation. One can make the argument that a planned awake intubation based on an airway evaluation combined with history and imaging studies suggestive of being potentially challenging is not something to be avoided, and in fact can be beneficial on many fronts. First, it is a safe approach, and it avoids the uncertainty with PEAE as discussed in #1 above. Second, it is an opportunity for the anesthesiologist to enhance his/ her experience with this technique that will be beneficial for this patient (and others) if they end up coming back for additional care, especially, if their airway pathology has progressed such that awake intubation is now a must. Such added experience will not only improve success rate with the technique, but also decrease the time it takes to almost the same time a standard anesthesia induction would take, and perfect the technique resulting in much improved patient comfort, and safety; from extensive personal and close colleagues’ experience practicing the technique almost on a daily basis and teaching it to hundreds of trainees over a span of 2 decades. In conclusion, there is no such a thing as unnecessary awake intubation when difficult intubation is highly suspected and/or anticipated such as the ENT airway. It is also claimed that the PEAE would save time, personnel and equipment wasted doing awake intubation6. The PEAE itself takes a couple of minutes according to McAvoy and colleagues5, and is recommended to be done in the preoperative/operating room holding areas. However, such areas, if available, are not usually as well equipped as an OR for handling emergencies, not to mention the lack of available staffing, at least in the majority of hospitals. Anesthesiologists are constantly engaged in some clinical activity; preoperative evaluation, intraoperative management, and postoperative follow up of coming, current and prior patients respectively. As for the equipment, cleaning and processing the scope used for PEAE is quite similar to that used for awake intubation, so no equipment savings can be perceived. On the contrary as in McAvoy and colleagues’ report5, another flexible scope and a videoscope were used to accomplish the successful asleep intubation in addition to the nasal scope used for the PEAE, which sums up to a much higher cost than using a single flexible or a rigid videoscope for an awake intubation approach. We have learned quite a bit from the NAP 4 study2,7. While the authors recommended the performance of preoperative nasendoscopy evaluation, they meant it for evaluation and appreciation of the anatomical relations of airway lesions and degree of obstruction and I might add if that was not obvious from what is discovered from history, airway examimnation and available imaging studies, and not as means to avoid “unnecessary awake intubations.” They further recommended against managing such airways away from the operating rooms, as suggested by PEAE adopters. One major argument against PEAE is that if the anesthesiologist has already tropicalized the nasal passages and was able to advance the scope to visualize the vocal cords, one can easily make the case for using a longer intubating scope and intubating this patient and not having to worry about making a decision regarding proceeding with or without awake intubation, especially given that the consequences of making a wrong assumption or decision can be grave. The original description of the PEAE6, and the current case report in this issue are authored by well-recognized airway management expert anesthesiologists with extensive expertise in the ENT airways so I trust that if they encounter difficulty with the intubation after a decision of inducing before securing the airway versus an awake intubation, they have the skills to manage the airway safely. On the other hand this may not apply to less experienced clinicanss7, who may not be specialized in or are used to dealing with complex “ENT airways” on a daily basis and thus may put some patients at risk. Therefore awake intubation may prove to be safer in those instances. The plethora of new airway devices namely videolaryngoscopes, and their documented benefits in improving laryngeal view, and intubation rates8 may explain the observed drop in the rates of difficult and failed intubation in the recent years9. However that rate is not zero: according to a large retrospective data base analysis, the current rate of difficult intubation is ∼1.6/1000, and failed intubation is 0.6/1000. Schechman et al10 reported a relatively high incidence of difficulty to intubate and 0.5% failure with GlideScope (Saturn Biomedical Systems, Burnaby, BC, Canada). This has been attributed for the most part to failure/difficulty to pass the tube despite adequate glottic view. As long as the rate is not zero, awake intubation technique should still be considered and utilized to mitigate this risk at least in the anticipated difficult ENT airway. Instead of proposing exploring the utility of PEAE to avoid “unnecessary awake intubations,” I would propose exploring performing more awake intubations, to enhance patients’ safety and improve experience with it. This can be accomplished by expanding the list of indications, to address some of the concerns with the physiologically difficult airway11, for example, in patients with very low pulmonary reserve, requiring high FiO2 supplementation (high oxygen delivery requirements, and or noninvasive ventilation) to maintain reasonable oxygen saturations, as they may not tolerate even a very brief period of apnea after induction of anesthesia. Another clinical conundrum that awake intubation can be helpful at is how to mitigate the aspiration risk in patients with full stomach. This is very relevant as the efficacy of the cricoid pressure as a part of the rapid sequence induction technique to avoid aspiration has been questioned12, and the aspiration rate as a complication of intubation is reported to be 0.04%9. Protective reflexes against aspiration include the glottic closure reflex13, which is only diminished and not abolished by topicalization14, and the cough reflex mediated by the rapidly adapting receptors (pulmonary irritant receptors) abundantly available in extra, and (mainly) intrapulmonary airways including the trachea and the main bronchi15. In the author’s experience and that of other airway experts that the standard airway topicalization does not block this protective cough reflex. Furthermore, the author limits topicalization to the oro/nasopharynx and does not perform transtracheal injection of local anesthetics out of extra caution to maintain most of the protective cough reflex and enable the patient to protect own airway in case aspiration occurs in the process. So perhaps one should consider awake intubation as the preferred technique in patients with very high risk for aspiration, such as post esophagectomy/stomach pull through and those with bowel obstruction, in order to avoid such a complication. It is worth noting that awake intubation does not have to be accomplished using a flexible fiberoptic/digital video scope, as it can be done with a variety of airway devices, like videolaryngoscopes. However, flexible scopes are tolerated the best among different airway intubation devices, and arguably the most successful in the ENT airway as they offer the capability of navigating around different tumors to get to the laryngeal inlet. However, when the flexible scope is used, the passage of the tube over the scope into the larynx is a blind maneuver and thus it may cause airway bleeding of friable tumor tissue, a generally accepted complication for securing a challenging airway. In conclusion, it might be beneficial to err on the side of safety and choose the awake intubation approach when a difficult airway is highly anticipated or suspected, especially when it comes to the difficult “ENT Airway.” Conflict of interest disclosures The author declares that there is no financial conflict of interest with regard to the content of this report.

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