[Literature reading] Why is awake endotracheal intubation still important?

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Why is it still important now? Awake intubation has been a cornerstone of difficult airway management ever since the use of awake intubation was advocated in the first guidelines published by the American Society of Anesthesiologists (ASA) Task Force on Difficult Airway Management
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Working group members cited the advantages of awake intubation—maintaining oxygenation and ventilation, maintaining upper airway muscle tone, and maintaining the position of oral, pharyngeal, hypopharyngeal, and laryngeal structures to minimize risk to the patient
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It is also recognized that awake intubation can cause patient discomfort and increase operative time, is complicated by airway obstruction during local anesthesia, and hypoxemia, hypercapnia due to concomitant use of sedative drugs and cardiovascular damage
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In addition, there have been many advances in airway management over the past few years, including the introduction of second-generation supraglottic devices and the widespread use of videolaryngoscopes
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Nonetheless, awake intubation still plays a role in modern airway practice
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A PubMed query for "Awake Tracheal Intubation" found 276 papers in the past 5 years, suggesting that awake intubation is still an important part of airway management and has academic interest
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In this review, we will provide a narrative overview of the recently published literature on awake intubation and demonstrate why it remains an important skill to master
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Risk of Adverse Events During Airway Management Airway management is complicated by emergencies of "no intubation, no oxygen and" which, if not rescued quickly, can lead to death or permanent brain damage
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In addition to those most catastrophic outcomes, airway injury or aspiration of gastric contents can occur during repeated, prolonged or challenging endotracheal intubation attempts
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Most elective surgical patients requiring airway management, as well as many emergency patients, initially present with adequate or at least minimal gas exchange
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These abilities are statically and phasically modulated by the central nervous system during awake and/or spontaneous breathing
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Induction of anesthesia makes these systems dependent on the ability of airway managers to maintain or restore their function
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Failure to do so could lead to disastrous results
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Therefore, the purpose of an airway manager's assessment of a patient's airway is to determine the risk of intubation failure
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However, airway assessment is an imprecise science
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Some assessments are less sensitive and less specific in their ability to identify high-risk patients
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Therefore, these authors suggest that the threshold for awake intubation for airway managers should be low when predictors of difficult airway management are present
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The ASA Difficult Airway Management Task Force has highlighted the need to consider awake intubation in its 2022 guidelines and added a decision tree tool to assist airway managers in routing
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This tool can help identify patients at high risk for airway management failure following induction of anesthesia (Figure 1)—those who may not be able to intubate quickly (for whatever reason) and who have one or more of the following: (1) Assessed as a risk of difficult mask or supraglottic airway ventilation; (2) as an increased risk of aspiration of gastric contents, (3) if gas exchange is disrupted and cannot be quickly corrected, rapid oxygen saturation or Risk of hemodynamic deterioration (ie "physiologically difficult airway"
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See Table 1 for clinical examples)
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When deciding whether to perform awake intubation, the 2022 guideline, compared with the previous version, emphasizes the risk of aspiration risk assessment and the risk of a physiologically difficult airway
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Figure 1 Pathways for awake endotracheal intubationTable 1 Risk factors for difficult airway management In the era of ubiquitous videolaryngoscopy, is awake intubation obsolete? The main means of Taoism management
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The fact that up to 7% of patients achieve unexpectedly poor laryngeal views with direct laryngoscopy, and the fact that this is greatly reduced with hyper-angle videolaryngoscopy is a strong basis for this argument
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In 2002, Ovassapian found that the main reason for the difficulty of direct laryngoscopy was the presence of hyperplastic lymphoid tissue at the base of the tongue
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Since the hyper-angle video laryngoscope bypasses the base of the tongue to create a view of the larynx, it is not surprising that these devices greatly reduce the difficulty of accidental intubation during direct laryngoscopy
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Furthermore, significant lingual tonsillar hyperplasia is not the only situation in which hyper-angle videolaryngoscopy excels in laryngeal visualization
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The use of videolaryngoscopes is helpful in obese patients, patients with higher-grade "modified Markovsky" views of the larynx, and other clinical situations
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In the opinion of these authors, the question of whether awake intubation is obsolete is reduced to the question of why it is a "difficult airway"
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As the saying goes, "difficult airway" refers to patients who are not difficult to use with endotracheal intubation and/or laryngeal mask/extraglottic ventilation, but experience unexpected difficulties in airway management
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With the widespread use of videolaryngoscopes, this type of "difficult airway" has certainly decreased
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But there are other causes of intubation difficulty, whether expected or not
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Videolaryngoscopy may not be the preferred device for patients with severe trismus, extreme neck deformity, and masses in the tongue, pharynx, hypopharynx, and larynx that distort the axis from mouth to larynx
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Likewise, in patients with a history of difficult airway management for no apparent reason, there may be other reasons why videolaryngoscopy is not amenable to management
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Although some patients with anatomical lesions and deformities unsuitable for videolaryngoscopy intubation can still be managed after induction of anesthesia, several clinical examples help illustrate the possible longevity of awake intubation and the need for clinicians to maintain this skill Sexuality: Limited Oral Access: When access to intubation via the oral route is limited or impossible (eg, in trismus), few existing tools in modern airway devices are suitable
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Chief among these is the range of flexible intubation, although blind nasotracheal intubation and video probe-assisted nasotracheal intubation have been reported
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Nasal intubation is associated with longer operative time and higher incidence of airway contamination (ie, blood) airway masses: In a study of patients with airway masses, 61% had one or more airway masses Complications of tract management: 23% required multiple laryngoscopy, 68% experienced mask ventilation difficulties, and 35% had oxyhemoglobin saturation less than 95% (including 8 patients treated with awake intubation) of 4)
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Although all 44 enrolled patients were intubated, the authors caution that despite the modern weaponry of airway management tools, techniques and drugs, this patient population remains challenging
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Neck lesions: Patients with limited neck mobility, scarring in the neck, a history of radiation, or a mass in the neck are at increased risk for difficulty intubation, and hyper-angle videolaryngoscopy may not overcome these limitations
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As noted above, due to one or more of the above clinical examples, the airway may not be reliably and rapidly protected, and may be difficult to ventilate, may be at risk of aspiration, or in patients at risk of desaturation and/or cardiovascular reactions, The safest method is awake intubation
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There is some evidence that awake intubation is underutilized, possibly due to concerns about patient comfort (although this is often exaggerated by clinicians), or lack of experience with the technique
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Several studies still demonstrate the continued use of awake intubation techniques in patients assessed as at risk
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For example, the awake intubation rate remained consistent at 1.
06% despite the increasing use of hyper-angle videolaryngoscopy at a major Canadian teaching hospital over an 11-year period
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Awake intubation rates were very similar in other centers in the US and UK, both 1.
0-1.
7%
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In the largest review of awake intubation, including more than 1000 events, common reasons for choosing awake intubation included trismus, reduced neck mobility, and previous difficulty with intubation
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Cervical instability is consistent with the factors outlined in the ASA Practice Guidelines for Difficult Airway Management, and cervical spondylosis with risk of neurological injury is another reason why airway managers may choose awake intubation – all endotracheal intubation and mask or SGA ventilation techniques Both pose a risk to an unstable cervical spine
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Traditionally, awake bronchoscopy has been the technique of choice for airway management in patients with cervical instability due to acute injury or degenerative disease
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The benefits of this technique are minimal neck movement and the ability to perform neurological examinations after intubation and before induction of anesthesia
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However, the use of awake fiberoptic intubation in the setting of cervical instability may have decreased in recent years due to the increased use of videolaryngoscopes
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Evidence on neurological impairment from airway management is limited to case reports, mostly in the setting of direct laryngoscopy without linear stabilization
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However, a recent report describes a patient with ankylosing spondylitis and severe valgus deformity who developed an artificial C5-6 dislocation fracture during intubation using a videolaryngoscope, resulting in hemiparesis
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Given the rarity of neurological impairments associated with airway management, direct comparative studies between techniques are not possible
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These authors argue that awake bronchoscopic intubation remains an important technique in the setting of severe cervical instability.
In the era of sugammadex, the introduction of the neuromuscular block reversal agent sugammadex has facilitated its use.
Reduced need for awake intubation techniques
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It has been suggested that induction of general anaesthesia in patients at risk of difficulty with airway management, which is considered safe with the use of nondepolarizing neuromuscular blocking agents, can be reversed with sugammadex at 16 mg/kg
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This technique may result in a shorter duration of neuromuscular block than when using succinylcholine
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Although limited in number, case reports have demonstrated successful rescues using this strategy
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However, there are multiple considerations that make this approach inappropriate
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First, the duration of conventional sedation-induced apnea was longer than the duration of rocuronium-sugammadex neuromuscular blockade and reversal
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Second, the determination that a non-intubation/non-oxygen condition has occurred may delay the decision to reverse the neuromuscular block
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Sugammadex at 16 mg/kg may prolong apnea by more than 6 minutes
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Third, differences in pre-oxygenation adequacy, patient-safe apnea duration, and physiologic tolerance of apnea may put some patients at high risk (eg, obese patients and pregnant patients).
How about awake videolaryngoscopy? Fiberoptic bronchoscopy is the most commonly used device for awake intubation, but alternative techniques include videolaryngoscopy, optical >
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Of note, nearly all studies comparing awake videolaryngoscopy excluded patients with restricted mouth opening, and few patients with oropharyngeal masses were included
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Therefore, the results of pooled analyses of these trials cannot be applied to these clinical situations
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Furthermore, given the overall success rate of awake intubation of 98-99%, even a meta-analysis with 355 participants was not large enough to detect awake intubation using a collapsible intubation scope versus videolaryngoscopy or other Differences between technology failure rates
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How about the combined technique of awake intubation? A combined videolaryngoscope and bronchoscopy intubation technique case report describes successful awake intubation using a combination of videolaryngoscopy and bronchoscopy when each fails when used independently
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This combination may be useful in the most challenging situations and creates a path for fiberoptic cannulation, as well as guiding fiberoptics
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Awake supraglottic airway-guided bronchoscopic intubation in 20 patients with morbid obesity plus 3 risk factors for difficult airway management (ie, 3 of the following: Mallampati grade 3 or 4, neck circumference ≥ 40 cm, thyroid distance < 6 cm, limited cervical spine mobility, limited mouth opening, limited mandible, missing teeth, beard or history of snoring)
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Another case series involving 10 supraglottic airway-guided flexible endoscopic intubations included patients with a history of difficult intubation, head and neck lesions, and/or limited cervical spine mobility
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In this regard, the proposed benefit of the supraglottic airway is to open the upper airway and clear the passage of secretions and blood
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The authors of these case series suggest that further studies should be conducted to determine whether this technique improves the first-time success rate of fiberoptic intubation in 93-96% of cases
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Disadvantages of this technique may include trauma from supraglottic airway insertion, complicating further attempts at airway management, the need for adequate mouth opening, and the inability to use for nasal intubation
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These authors believe that further research is needed before awake supraglottic airway-guided fiberoptic intubation is selected as the primary technique in routine settings
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Skills to Gain and Stay Awake Intubation Are Awake Intubation Safe in the Age of COVID? The first case report on awake intubation of a patient suspected of COVID-19 was published online in early May 2020
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The group described sedation with target-controlled infusion of propofol and remifentanil to minimize cough, followed by topical treatment of the nasopharynx with a 2.
5ml co-benzcaine spray, administered via a mucosal nebulizer.
Topical treatment of the oropharynx with 10% lidocaine
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Two subsequent case reports described other topical approaches
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In October 2021, the Airway Management Association issued a statement on difficult airway management in patients with COVID-19
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The statement discusses awake endotracheal intubation, recognizing that the increased time and complexity of awake intubation may increase the risk of oxygen desaturation in the patient and exposure to infectious bacteria of the team performing the intubation
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Therefore, they recommend that awake intubation is warranted by a provider experienced in advanced airway techniques
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If determined to be necessary, anti-salivary medication should be administered followed by judicious sedation to reduce coughing under local anesthesia
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Topical treatment techniques with which the operator is most familiar should be used
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Further recommendations include the use of disposable plastic intubation scopes when available, suction through the working channel in oxygen deficient conditions, and transoral intubation where feasible
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Notably, these recommendations are based on expert opinion rather than high-level evidence, but they provide practical guidance for awake endotracheal intubation in the risky setting of the COVID-19 pandemic
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SUMMARY Despite the advent of new airway devices and techniques, the literature is still replete with descriptions of the use of awake intubation to treat patients with difficult airways
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The criteria set forth in the 2022 ASA guidelines instruct airway managers to consider the awake intubation approach based on their own experience and practice environment
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Two clinicians, each with different skills and experience, may correctly choose different paths
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Awake intubation is successful in 98-99% of cases and remains a reliable method of airway management in the presence of trismus, oropharyngeal masses, and cervical immobilization
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Newer techniques have been described in the literature over the past few years, including awake videolaryngoscopy, combined videolaryngoscopy-bronchoscopy, and combined supraglottic airway-bronchoscopy
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More research is needed to determine the patient populations and settings best suited for these techniques
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Notes/AwakeIntubationTechniquesAndWh.
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