Tom Wade MD

In addition to today’s resource, please review *The Best Teaching Video of “Cricothyrotomy – Scalpel-Bougie-Tube technique” With Links To Additional Resources
Posted on July 16, 2024 by Tom Wade MD.

In addition to today’s resource, please review 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.

Today, I review, link to, and excerpt from 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.

All that follows is from the above resource.

Abstract

Purpose

Since the last Canadian Airway Focus Group (CAFG) guidelines were published in 2013, the literature on airway management has expanded substantially. The CAFG therefore re-convened to examine this literature and update practice recommendations. This first of two articles addresses difficulty encountered with airway management in an unconscious patient.

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 was lacking, statements are based on group consensus.

Findings and key recommendations

Most studies comparing video laryngoscopy (VL) with direct laryngoscopy indicate a higher first attempt and overall success rate with VL, and lower complication rates. Thus, resources allowing, the CAFG now recommends use of VL with appropriately selected blade type to facilitate all tracheal intubations. If a first attempt at tracheal intubation or supraglottic airway (SGA) placement is unsuccessful, further attempts can be made as long as patient ventilation and oxygenation is maintained. Nevertheless, total attempts should be limited (to three or fewer) before declaring failure and pausing to consider “exit strategy” options. For failed intubation, exit strategy options in the still-oxygenated patient include awakening (if feasible), temporizing with an SGA, a single further attempt at tracheal intubation using a different technique, or front-of-neck airway access (FONA). Failure of tracheal intubation, face-mask ventilation, and SGA ventilation together with current or imminent hypoxemia defines a “cannot ventilate, cannot oxygenate” emergency. Neuromuscular blockade should be confirmed or established, and a single final attempt at face-mask ventilation, SGA placement, or tracheal intubation with hyper-angulated blade VL can be made, if it had not already been attempted. If ventilation remains impossible, emergency FONA should occur without delay using a scalpel-bougie-tube technique (in the adult patient). The CAFG recommends all institutions designate an individual as “airway lead” to help institute difficult airway protocols, ensure adequate training and equipment, and help with airway-related quality reviews.

Keywords: guidelines, airway management, difficult, failed, intubation, tracheal

Disclaimer

These recommendations aim to reflect the latest published evidence regarding airway management. Where high-quality evidence is lacking, expert opinion and consensus is presented. The recommendations do not represent standards of care, and instead are suggestions for optimal practice. They should be applied with specific consideration of the individual patient’s characteristics, the clinical context, the airway manager’s skills, available resources, and local institutional policies.

Introduction

Morbidity related to airway management continues to be reported in closed legal claims1,2 and practice audits.3,4 When such adverse airway outcomes are subject to peer review and analysis, patterns of care are often found to be suboptimal.1–3 Common themes include persistence with one technique when tracheal intubation proves difficult; failure to recognize an evolving “cannot ventilate, cannot oxygenate” (CVCO) scenario and failure to perform timely emergency front-of-neck airway access (eFONA) when indicated. Failure of non-technical skills such as effective communication and good team dynamics have often also contributed to airway-related morbidity.1–3 With previous guidelines published in 19985 and 2013,6,7 this update to Canadian airway management recommendations reflects new evidence and opinion appearing in the literature. It applies to difficulty encountered with airway management in an unconscious and often apneic patient.

Significant difficulty with airway management in the unconscious patient can often be avoided by careful airway evaluation before the induction of general anesthesia. In part 2 of these updated recommendations,8 we have addressed decision-making and implementation of the planned airway strategy for the patient with an anticipated difficult airway. Recommendations in both articles are meant to be broadly applicable to all specialties involved in airway management.

Methods

The Canadian Airway Focus Group (CAFG) comprises 17 members (see Appendix), with representation from across Canada as well as one member each from New Zealand and Australia. The CAFG membership includes anesthesiologists, emergency physicians, and critical care physicians. Topics for review were divided among the members, with most assigned to two members. Members reviewed the literature published from 2011 onwards.

A medical librarian helped design and conduct the literature searches. Though not constituting a formal systematic review, databases searched included Medline, EMBASE, Cochrane Central Register of Controlled Trials, and CINAHL. Non-English and non-French, animal, manikin, and cadaver studies were excluded, as were case reports, editorials, and letters. Nevertheless, team members had discretion to include such material where relevant.

The CAFG met every two weeks via videoconference from April 2018 to July 2020 to review findings and arrive at consensus regarding recommendations. Similar to other airway management guidelines,9–12 we did not assign levels of evidence or strength of recommendation. This follows from a lack of what is considered high-level evidence seen in other medical fields. Randomized controlled trials of airway devices typically address efficacy (often in a population of low-risk elective surgical patients) but when critical events are uncommon (as with airway management), they are unable to evaluate the safety of techniques or decision-making.13 Information gleaned from large database studies is better able to capture uncommon events,13 but analysis is limited to association rather than causation, and the population studied may not represent all practice environments. Thus, although evidence-based to the extent possible, some of the recommendations that follow are based largely on expert consensus.

After review by the CAFG, draft documents were sent to several international airway experts (see Acknowledgments) for informal review and comment.

Definitions

The following definitions are used throughout the manuscript:

• Difficult airway. A difficult airway exists when an experienced airway manager anticipates or encounters difficulty with any or all of laryngoscopy or tracheal intubation, face-mask ventilation (FMV), supraglottic airway (SGA) use, or eFONA. The airway extends from the nostrils and lips to the alveoli, and anatomical variation or pathological distortion anywhere along its length may cause difficulty. Physiologic or contextual issues may compound difficulty with airway management.
• Difficult and failed face-mask ventilation. Difficulty with or the failure of FMV can be described according to the four-grade scale presented in Table 1.14,15 Grades 3 and 4 correspond to difficult and failed ventilation, respectively. The CAFG does not include the number of hands used for a mask seal (i.e., 1 vs 2) in its definition of difficulty, recognizing that the use of two hands may simply reflect clinician preference or the need to optimize a seal to minimize patient exhalation/air leak to the environment.

• Difficult and failed supraglottic airway use. Supraglottic airway use is difficult when more than one attempt at insertion is required, or the resulting ventilation is inadequate. Failed use of an SGA is defined by inadequate ventilation and oxygenation after a maximum of three attempts. As with FMV, this will be reflected by an absent or severely attenuated capnography trace.

• Difficult and failed supraglottic airway use. Supraglottic airway use is difficult when more than one attempt at insertion is required, or the resulting ventilation is inadequate. Failed use of an SGA is defined by inadequate ventilation and oxygenation after a maximum of three attempts. As with FMV, this will be reflected by an absent or severely attenuated capnography trace.
• Difficult and failed direct or video laryngoscopy. The view obtained during direct laryngoscopy (DL) or video laryngoscopy (VL) is typically quantified using the Cormack-Lehane16 grade or one of its modifications17,18 (Table 2). Secretions, blood, emesis, and fogging or illumination issues can also cause difficulty with laryngoscopy. Difficult laryngoscopy is generally described as a Cormack–Lehane grade 2b or 3a view and does not necessarily imply that difficult or failed tracheal intubation will follow. Grade 3b and 4 views define failed DL or VL.

• Difficult and failed tracheal intubation. Tracheal intubation is considered difficult if more than one attempt at optimized laryngoscopy and tracheal tube passage is made, a more experienced operator is required, or a change is made in technique/device. Tracheal intubation has failed if the patient is not intubated after a maximum of three attempts by an experienced airway manager. The definition of failed intubation exists not to be pejorative, but to serve notice to the airway manager that help should be sought and an alternate course of action pursued.
• “Cannot ventilate, cannot oxygenate”. The CVCO situation has occurred if attempts to ventilate the patient with all three of tracheal intubation, FMV, and an SGA have failed (i.e., cannot ventilate), resulting in imminent or current hypoxemia (i.e., cannot oxygenate). After much discussion, the CAFG has chosen to introduce the term CVCO rather than referring to “cannot intubate, cannot oxygenate” (CICO) for two reasons. First, it helps de-emphasize what may have been an inappropriate focus on tracheal intubation given that the physiologic endpoints of ventilation and oxygenation are the more important goals. Historically, this might have led to persistence with multiple futile attempts at tracheal intubation in the imminently or already hypoxemic patient and may have failed to prompt an attempt at ventilation using an SGA. Secondly, it acknowledges that the absent or severely attenuated waveform capnography that accompanies each of failed tracheal intubation, FMV, and SGA use (i.e., cannot ventilate) will sometimes precede significant oxygen desaturation, especially in the well pre-oxygenated patient (or possibly, when apneic oxygenation is in use). This window of imminent hypoxemia, between the recognition of the “cannot ventilate” situation and the onset of severe hypoxemia offers the best opportunity for a good patient outcome by promptly performing eFONA.
• Emergency front-of-neck airway access*. This refers to emergency access to the trachea via the front of the neck by either cricothyrotomy or tracheotomy. In the hands of non-surgeons, eFONA most often occurs in the adult patient by cricothyrotomy and is considered difficult if it requires more than one attempt.

*The Best Teaching Video of “Cricothyrotomy – Scalpel-Bougie-Tube technique” With Links To Additional Resources
Posted on July 16, 2024 by Tom Wade MD

Incidence of difficult and failed airway management

Table 3 outlines data from studies in various contexts reporting the frequency of difficult and/or failed FMV, SGA use, tracheal intubation, and eFONA. The studies from which these data are taken are heterogeneous, with inconsistent variables such as patient population, airway manager experience, definitions of difficulty or failure, and the use of neuromuscular blockade. This is likely to explain some of the table’s wide-ranging numbers.

Response to difficulty with airway management in the unconscious patient

Airway managers should be ready with a pre-planned, stepwise approach to managing difficulty with FMV, SGA use, or tracheal intubation.

Response to difficult FMV

Difficult FMV is challenging to reliably predict,19 and is often indicated by an attenuated waveform capnography trace.15,71 Options for responding to difficult FMV are presented in Table 4.

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