Linking To And Excerpting From Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 2. Planning and implementing safe management of the patient with an anticipated difficult airway

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In addition to today’s resource, please review Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 1. Difficult airway management encountered in an unconscious patient. [PubMed Abstract] [Full-Text HTML[ [Full-Text PDF]. Can J Anaesth. 2021 Sep;68(9):1373-1404. doi: 10.1007/s12630-021-02007-0. Epub 2021 Jun 18.

Today, I review, link to, and excerpt from Canadian Airway Focus Group updated consensus-based recommendations for management of the difficult airway: part 2. Planning and implementing safe management of the patient with an anticipated difficult airway. [PubMed Abstract] [Full-Text HTML] [Full-Text PDF]. Can J Anaesth. 2021 Sep;68(9):1405-1436. doi: 10.1007/s12630-021-02008-z. Epub 2021 Jun 8.

All that follows is from the above resource.

Abstract

in English, French

Purpose: Since the last Canadian Airway Focus Group (CAFG) guidelines were published in 2013, the published airway management literature has expanded substantially. The CAFG therefore re-convened to examine this literature and update practice recommendations. This second of two articles addresses airway evaluation, decision-making, and safe implementation of an airway management strategy when difficulty is anticipated.

Source: Canadian Airway Focus Group members, including anesthesia, emergency medicine, and critical care physicians were assigned topics to search. Searches were run in the Medline, EMBASE, Cochrane Central Register of Controlled Trials, and CINAHL databases. Results were presented to the group and discussed during video conferences every two weeks from April 2018 to July 2020. These CAFG recommendations are based on the best available published evidence. Where high-quality evidence is lacking, statements are based on group consensus.

Findings and key recommendations: Prior to airway management, a documented strategy should be formulated for every patient, based on airway evaluation. Bedside examination should seek predictors of difficulty with face-mask ventilation (FMV), tracheal intubation using video- or direct laryngoscopy (VL or DL), supraglottic airway use, as well as emergency front of neck airway access. Patient physiology and contextual issues should also be assessed. Predicted difficulty should prompt careful decision-making on how most safely to proceed with airway management. Awake tracheal intubation may provide an extra margin of safety when impossible VL or DL is predicted, when difficulty is predicted with more than one mode of airway management (e.g., tracheal intubation and FMV), or when predicted difficulty coincides with significant physiologic or contextual issues. If managing the patient after the induction of general anesthesia despite predicted difficulty, team briefing should include triggers for moving from one technique to the next, expert assistance should be sourced, and required equipment should be present. Unanticipated difficulty with airway management can always occur, so the airway manager should have a strategy for difficulty occurring in every patient, and the institution must make difficult airway equipment readily available. Tracheal extubation of the at-risk patient must also be carefully planned, including assessment of the patient’s tolerance for withdrawal of airway support and whether re-intubation might be difficult.

Keywords: airway management; anticipated; difficult; guidelines; intubation; tracheal.

© 2021. The Author(s).

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Introduction

Significant morbidity related to airway management continues to be reported, with the failure to plan for difficulty a recurrent theme.1–3 Most published airway guidelines focus on management of the already-unconscious patient when difficulty with tracheal intubation is encountered. Although less frequently addressed, avoiding having to manage an unexpectedly difficult airway almost certainly has greater potential to prevent patient harm. Airway-related morbidity can be prevented by careful patient evaluation and formulation of an airway management strategy (a co-ordinated series of plans) before proceeding with airway management. Lack of an airway evaluation or the failure to change usual practice based on its findings has been associated with morbidity.1 Airway evaluation includes examination for anatomic predictors of difficulty with tracheal intubation, face-mask ventilation (FMV), supraglottic airway (SGA) use, and emergency front of neck airway access (eFONA). It should also include assessment of physiologic issues (e.g., apnea tolerance, aspiration risk, and altered hemodynamics) and the clinical context (e.g., case urgency, airway manager experience, equipment availability, and access to expert assistance). Airway evaluation should occur before starting airway management as well as before its discontinuation.

Video laryngoscopy (VL) has helped achieve more consistent glottic visualization and has improved first-attempt intubation success rates in the unconscious patient, especially in populations deemed to be at risk for difficult direct laryngoscopy (DL).4 Nevertheless, there remain patients who, based on thorough airway evaluation, would likely be more safely managed with awake tracheal intubation. This article addresses airway evaluation and provides recommendations to help formulate and implement a safe airway management strategy when difficulty is anticipated. In part 1 of these updated two-part recommendations,5 we address management of airway difficulties encountered in the unconscious patient, whether anticipated or not. Recommendations in both articles are meant to be broadly applicable to all specialties that have airway management in their practice mandate.

Definitions

The following definitions are used throughout the manuscript.

• Anticipated difficult airway. A difficult airway is predicted when the airway manager anticipates difficulty with any or all of FMV, tracheal intubation, SGA use, or eFONA.
• Awake tracheal intubation. Awake tracheal intubation (ATI) refers to tracheal intubation of a patient who is sufficiently conscious to maintain a patent airway unassisted, to maintain adequate gas exchange by spontaneous ventilation, and to protect the airway against the aspiration of gastric contents or other foreign material. Awake tracheal intubation can occur via the nasal, oral, or front of neck routes, and is facilitated by topical, regional, or local infiltrative airway anesthesia.
• At-risk tracheal extubation. The at-risk tracheal extubation is defined by the patient anticipated to be intolerant of tracheal extubation or who might be potentially difficult to re-intubate. Difficult re-intubation might be anticipated based on pre-existing or de novo conditions (e.g., neck fusion or immobilization; upper airway edema).

Prediction of difficulty with airway management

Predicting difficulty underlies the planning for safe airway management. Expert opinion appearing in audits of airway-related morbidity and closed legal claim studies suggest that the “failure to prepare for failure” by omitting, not documenting, or not acting on positive findings of an airway evaluation figures prominently in cases with poor outcomes.1–3 Canadian data,3 and that from the USA,2 reveal that most anesthesia airway-related closed claims involved patients presenting for elective surgery (78% and 63%, respectively).

Comprehensive airway evaluation includes physical examination of the patient and review of relevant physiologic and contextual issues, pertinent diagnostic imaging studies, and any available records of previous airway management. A history of previous difficulty is more often correctly predictive of difficulty than the bedside examination.11–15

Alone or in combination, the various bedside screening tests of anatomic features have been criticized for their poor performance in correctly predicting when difficulty will indeed occur with airway management.11,13,16 Nevertheless, the presence of certain anatomic features (Tables 1, ​,2,2, ​,3,3, ​,4,4, ​,5,5, ​,6,6, ​,7)7) should alert the airway manager to carefully consider the safest approach to airway management and which devices to have available; little downside will accrue if airway management turns out to be non-problematic. Conversely, when bedside screening suggests that no difficulty is expected, while more often correctly predictive of the actual outcome,11,16,17 unanticipated difficulty can still occur, such that the airway manager must be ready with a strategy to address difficulty in all patients. Performing and documenting an airway evaluation is standard of care, and furthermore, acts as a cognitive prompt18 to consider the potential for difficulty with every patient. The CAFG recommends that all patients undergo airway evaluation before the initiation of airway management and before the discontinuation of airway support (e.g., tracheal extubation).

Published predictors of difficult airway management

Predictors of difficult tracheal intubation by DL and VL and other devices appear in Tables 1–3. Predictors of difficult FMV and difficult SGA use appear in Tables 4 and ​and5,5, respectively. Predictors of difficult eFONA have not been prospectively studied but appear on a presumptive basis in Table 6. The likelihood of actually encountering difficulty with any modality increases in proportion to the number of anatomic predictors of difficulty.

There are currently few published studies looking at predictors of difficulty with tracheal intubation using VL; this is a gap in the literature that should be addressed. Physiologic and contextual factors that may also impact planning and implementation of airway management appear in Table 7.

The enhanced airway evaluation

Patients with obstructing airway pathology may have distortions of upper or lower airway anatomy that cannot be identified by regular bedside screening tests. For the patient with known or suspected obstructing glottic or supraglottic airway pathology, awake nasal endoscopy or oral VL performed under local anesthesia immediately before airway management can help clarify the extent and location of the problem.19 Subglottic pathology can be assessed by review of recent imaging studies.20 Point-of-care ultrasound is playing an increasing role in physiologic diagnosis and evaluation of targeted management of resuscitation before, during, or after airway management.21

Another aspect to enhancing the airway exam in patients with significantly altered anatomy is to identify the location of the cricothyroid membrane (CTM).22 If visual inspection or palpation fails to identify the CTM location with certainty, it should be identified using ultrasonography and marked,22,23 with the patient’s neck in an extended position. The patient can subsequently be positioned optimally for the intended airway technique; if eFONA is required, the patient can quickly be returned to the neck-extended position to utilize the previously made marking.24

Decision-making when difficult tracheal intubation is predicted

Few published studies or guidelines specifically address which patients with predictors of difficult tracheal intubation can safely be managed after the induction of general anesthesia. Nevertheless, cues can be taken from the UK’s NAP4 study1 and closed claims analyses.2,3 In NAP4, ATI was judged to have been underutilized in patients with known difficult airways. Eighteen cooperative patients with predictors of both difficult tracheal intubation and difficult FMV underwent intubation attempts after induction of general anesthesia. All suffered complications and two patients died.1

When difficulty is predicted, ATI enables patients to maintain their own airway patency, gas exchange, and protection of the lower airway against aspiration during tracheal intubation; thus, ATI potentially provides a safety benefit. Conversely, despite possessing predictors of difficult laryngoscopy or intubation, some patients might still be safely managed after induction of general anesthesia. When difficult laryngoscopy or intubation is predicted, deliberate consideration of the following four questions can help the airway manager decide whether ATI is indicated or if management might safely occur after induction (Fig. 1).

Fig. 1

Flow diagram: Decision-making when difficult tracheal intubation is predicted. ATI = awake tracheal intubation; DL = direct laryngoscopy; FMV = face-mask ventilation; SGA = supraglottic airway; VL = video laryngoscopy.

A. Does the patient clearly need awake tracheal intubation?

Significant and obvious anatomic deformities or pathologic alterations of the head and neck are often most safely managed with ATI. Examples include (but are not limited to) the patient with very limited mouth opening, a fixed flexion deformity of the head and neck, or a pathologically enlarged tongue. In such patients, there is often no chance that standard techniques such as DL, Macintosh blade video laryngoscopy (Mac-VL) or hyper-angulated blade VL (HA-VL) are feasible. Alternatives to these standard techniques are likely to be less familiar to the airway manager or take longer to use, especially in the context of distorted anatomy. Thus, if managing the airway in apneic conditions after induction of general anesthesia, this could put the patient at risk of significant hypoxemia. In addition, anatomy altered to this extent will often also predict difficulty with fallback modes of ventilation such as FMV or SGA use (see next section). For these reasons, ATI is a safer option.

B. Is difficulty also predicted with fallback ventilation options?

When difficult tracheal intubation is predicted, no matter how effective the primary device chosen to facilitate tracheal intubation may be, all have a failure rate. When this occurs, FMV or SGA ventilation will be needed between attempts. Unfortunately, when difficult or failed tracheal intubation has occurred, difficult FMV is more likely,55–57 and vice versa.46,57 Similarly, failed SGA ventilation is associated with a higher incidence of difficult FMV.49,52 This phenomenon has been referred to as the “composite failure of airway management”.55 Tracheal intubation and FMV are reported to have predictors of difficulty common to both modalities44 (Table 4). Thus, when difficulty is predicted with one mode (e.g., tracheal intubation), the airway manager must be especially vigilant in assessing the patient for predicted difficulty with other modes (e.g., FMV, SGA ventilation, or front of neck airway access [FONA]). When significant difficulty is predicted with two or more modes, (e.g., tracheal intubation and FMV), ATI should be strongly considered as a potentially safer option.

C. Is there any physiologic compromise?

Physiologic compromise (Table 7) complicates and distracts from difficult airway management.53,54 It is also accentuated by induction of anesthesia that additionally risks hypoxemia, aspiration, or hemodynamic instability in those at risk. Separation of difficult airway management from induction of anesthesia is therefore of value; thus, ATI is likely the optimal choice for both safety and controlling the cognitive load of the airway manager.

Rarely, physiologic issues might be the sole indication for ATI, without any anatomic predictors of difficulty with airway management, as with a critically ill patient with significant lung parenchymal disease and a high shunt fraction.58

D. Are there any complicating contextual issues?

Contextual issues (Table 7) might also favour ATI when difficult tracheal intubation is predicted. For example, when an airway manager is practicing in a resource-austere setting without access to expert assistance or VL, the use of ATI for the predicted difficult airway patient might improve the margin of safety if patient transfer to a more fully equipped facility is not an option.

As indicated in Fig. 1, if all of the preceding questions are answered in the negative, airway management after induction of general anesthesia may be considered. Nevertheless, it must be emphasized that this decision remains one of clinical judgement and that the algorithm based on these questions has not been validated in a randomized-controlled trial. An airway manager’s individual threshold for performing ATI or other patient or system factors might also impact the decision. Conversely, if the pathway through the Figure 1 flow diagram has suggested that ATI might be a safer option, a fifth question must then be addressed, as follows.

Can the patient cooperate with ATI and is there time?

Proceeding with ATI generally requires both a cooperative patient and time for its completion. If these are lacking, options become more limited. In some critically ill patients, physiologic disturbances or an alteration in sensorium can make compliance with ATI challenging. This may guide the airway manager towards tracheal intubation after the induction of general anesthesia if airway management must proceed at that time (Fig. 1). Under these circumstances, regardless of how the induction of general anesthesia proceeds (e.g., with or without an attempt to maintain spontaneous ventilation), “double set-up” (Table 8) preparations for eFONA are recommended in case of need. This decision must be balanced against the benefit of delaying tracheal intubation in favour of less invasive approaches for ventilation/oxygenation or further medical management, if this is an option.