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Airway management for induction of general anesthesia

Airway management for induction of general anesthesia
Literature review current through: Jan 2024.
This topic last updated: Nov 28, 2023.

INTRODUCTION — Airway management is a crucial skill for the anesthesia clinician. It is an integral part of general anesthesia, allowing ventilation and oxygenation as well as a mode for anesthetic gas delivery. Major complications of airway management in the operating room are very rare but may be life threatening.

This topic will discuss the formulation of an airway management strategy for general anesthesia, including plans for the use of mask ventilation, use of supraglottic airway devices (SGA), endotracheal intubation, and the selection of medications for induction of general anesthesia. Techniques and devices for airway management, rapid sequence induction intubation, and management of the difficult airway are discussed separately.

(See "Rapid sequence induction and intubation (RSII) for anesthesia".)

(See "Management of the difficult airway for general anesthesia in adults".)

AIRWAY ASSESSMENT — All patients undergoing general anesthesia should have a complete history and anesthesia-directed physical examination. One goal of this evaluation is to predict the degree of difficulty with mask ventilation and endotracheal intubation using standard devices. The plan for airway management follows from this prediction, since in many cases induction of anesthesia will result in airway obstruction and at least temporarily make the patient apneic. In addition, factors that predispose the patient to aspiration during anesthesia should be identified.

Airway history — For patients who report problems with anesthesia in the past, every effort should be made to obtain and review prior anesthesia records for details of airway management.

A number of disease states, both congenital and acquired, have been associated with difficult airway management (table 1). In addition, pulmonary problems such as asthma, recent upper respiratory infection, pneumonia, bronchitis, or presence of chronic obstructive pulmonary disease (COPD) may impact oxygenation and ventilation during induction [1].

Most patients who present for emergency procedures are at increased risk of aspiration during anesthesia, either because of recent oral intake or because of predisposing conditions (table 2). In addition, the incidence of difficult intubation is significantly higher in the emergency department and other areas outside of the operating room. (See "Approach to the difficult airway in adults for emergency medicine and critical care".)

Airway examination — A number of bedside tests and measurements have been developed to evaluate the airway (table 3). Though they are and should be routinely used, they are of limited value in predicting difficult mask ventilation and intubation (see 'Prediction of the difficult airway' below):

First glance assessment – The preoperative first glance assessment provides significant useful information. Obesity, facial hair, a thick, short neck, and neck collars are immediately apparent and suggest potential difficulty with airway management.

Mouth opening Mouth opening is usually assessed in finger breadths. A mouth opening of less than three finger breadths is considered limited. Patients with temporomandibular joint (TMJ) disease or prior surgery may have very limited mouth opening or trismus. Radiation of the head and face can also result in trismus or scarring that distorts the anatomy or limits mobility.

Dentition should be assessed, with particular attention to the presence of caps, crowns, implants, veneers, dentures, braces, or loose teeth. These should be documented and the risk of damage discussed with the patient. Dentures should ordinarily be removed in the preoperative area before the patient is brought to the operating suite. However, if mask ventilation is planned, dentures may be left in place to improve mask fit, though they should be removed immediately prior to intubation to prevent dislodgement or damage. If the patient has braces, the risk of soft tissue injury to the lips during airway management should be discussed.

Mallampati class Mallampati class was first described in 1985 as a test to predict difficult laryngoscopy [2]. The Mallampati evaluation originally included three classes based on the ability to view the tonsillar pillars, uvula, and palate with the mouth open and the tongue protruded. The more widely used modified Mallampati class includes a fourth class (figure 1) [3]:

Class I: The entire tonsillar pillars, uvula, hard and soft palates are visualized

Class II: Partial uvula and soft palate are visualized

Class III: Only the soft palate is visualized

Class IV: No visualization of any structures beyond the tongue

A Mallampati class 0 has also been described, in which part of the epiglottis can also be seen upon mouth opening in addition to all the class I structures listed above [4,5].

The Mallampati test was initially described with the patient in the sitting position. Studies comparing performance of the test supine with sitting have shown conflicting results, with some reporting an increase in Mallampati class in the supine position [6], some a decrease [7], and some no change [8]. Two single-center studies reported that the score in the supine position improved the predictive value for difficult intubation [9,10].

The original description of the Mallampati test did not specify whether the patient should phonate during the test. Most studies have reported that phonation alters the score and reduces the sensitivity of the test (ie, phonation falsely lowers the Mallampati score) [7-9].

We routinely perform the Mallampati evaluation in the sitting position, and perform the test in the supine position if the patient is unable to sit up. We perform the test without phonation.

Thyromental distance Thyromental distance (TMD) is the distance between the thyroid cartilage and the mandible, measured in full extension of the neck. Short TMD has been defined as less than 6 cm. Historically, TMD has been used as a rough estimate of the submental space, which is the space that must accommodate the tongue during laryngoscopy [11,12].

Sternomental distance Sternomental distance is measured between the sternal notch and the mandible, measured in full neck extension. Short sternomental distance is defined as less than 12 cm. This parameter and TMD may be objective surrogates for adequacy of neck extension [13].

Neck range of motion – Both neck flexion and extension should be assessed for limitations. Patients with arthritis of the neck, cervical spine disease, or previous spine surgery may have limited neck extension. Studies have shown that neck range of motion decreases with age, and decreased neck extension has been associated with difficulty with airway management [14]. Patients with restricted neck extension may be more difficult to optimally position for induction of anesthesia and intubation.

Mandibular protrusion Patients are asked to protrude the lower jaw such that the mandibular teeth are in front of the maxillary teeth, as a predictor of the ability to sublux the mandible during laryngoscopy. A more objective, similar measurement is the upper lip bite test (ULBT), which assesses the patient's ability to reach and cover the upper lip with their lower incisors. ULBT grading includes [15,16]:

Grade 1: The patient can fully cover the upper lip with lower incisors

Grade 2: The patient can partially cover the upper lip with lower incisors

Grade 3: The patient cannot reach the upper lip with lower teeth

Advanced methods of airway assessment — Endoscopy and ultrasound have limited application for routine airway assessment [11,17]. For patients with known or suspected distortions of airway anatomy, these techniques as well as radiologic imaging may be useful before airway management is undertaken.

Preoperative endoscopy – Preoperative airway endoscopy, which has been used by otolaryngologists for many years to diagnose airway pathology, can also be used for preoperative airway assessment. Endoscopy provides visualization of internal airway anatomy that cannot be viewed with external tests. Routine preoperative airway endoscopy is not indicated for patients undergoing elective surgery unless abnormal airway anatomy is suspected [18].

Ultrasound – With increasing availability of bedside ultrasound in the operating room, ultrasound has been used for airway assessment. It can allow visualization of the airway from the mouth to mid-trachea, and can also be used to identify the cricothyroid membrane, visualize the vocal cords, and identify airway pathology [19-21]. The use of ultrasound examination to predict difficulty with intubation has not been fully studied [22-24]. In a meta-analysis 10 studies (1812 patients) that evaluated the utility of ultrasound for predicting difficult laryngoscopy during anesthesia in patients without other indicators or a history of difficulty, the distance from the skin to the epiglottis accurately predicted difficult laryngoscopy (sensitivity 0.82, specificity 0.79) [22]. However, the quality of the data was judged to be very low to low due to high heterogeneity.

PREDICTION OF THE DIFFICULT AIRWAY

Anatomically difficult airway — Most difficulty with airway management is not predicted in advance. This was demonstrated in a retrospective review of over 188,000 cases in Denmark [25]. Of difficult intubations, 93 percent were unanticipated; 94 percent of cases of difficult mask ventilation were unanticipated.

An analysis of data from 2016 to 2021 from the Difficult Airway Society Difficult Airway Database found that approximately half of difficult airway events were unanticipated, despite performance of airway assessment [26].

Numerous investigators have attempted to predict difficulty with airway management based on the bedside airway assessment described above. Single tests are of limited value for predicting the difficult airway [25,27-29], though combinations of tests add some diagnostic accuracy [4,17]. At the very least, this preoperative airway assessment forces the clinician to think about potential difficulty with airway management.

Difficult mask ventilation — The incidence of difficult mask ventilation for anesthesia in the general surgical population is between 0.9 and 5 percent, depending on the definition of difficulty [30-33]. For our purposes, we will define difficult mask ventilation as the inability of an unassisted anesthesia clinician to maintain adequate oxygenation or reverse signs of inadequate ventilation.

Prospective studies have variably identified the following risk factors for difficult mask ventilation (table 4) [30-32,34,35]:

Age older than 55

Body mass index (BMI) >26 or 30 kg/m2 (calculator 1)

Presence of a beard

Lack of teeth

History of snoring/sleep apnea

Abnormal neck anatomy

Male sex

Short thyromental distance (TMD) (<6 cm)

Severely limited mandibular protrusion

Mallampati class 3 or 4 (figure 1)

The presence of more than one risk factor significantly increases the chance of difficulty or failure of mask ventilation. Clinicians will not always be able to predict which patients will have difficult mask ventilation and patients with difficult mask ventilation are often more difficult to intubate. As an example, in one prospective study, only 17 percent of cases of difficult mask ventilation were predicted by the anesthesiologist [30]. In another study, intubation was difficult in one-quarter of patients with difficult mask ventilation, while the overall incidence of difficult intubation was approximately 5 percent [34].

Difficult supraglottic airway device use — Approximately 0.1 to 4.7 percent of attempts to manage the airway with a supraglottic airway (SGA) device will be unsuccessful [36]. Successful use of the SGA depends on selection of the appropriately sized device, more so than with the use of an endotracheal tube. The large number of brands and styles of available SGAs complicates the evaluation of failure. Some factors that may predict difficulty with SGA device placement or use include (table 5) [37-39]:

Small mouth opening (<3 finger breadths)

Neck radiation

Tonsillar hypertrophy

Fixed cervical spine flexion deformity

Applied cricoid pressure

Obesity

Poor dentition or large incisors

Male sex

Difficult intubation — The incidence of difficult direct laryngoscopy in patients with normal anatomy is approximately 5 percent in the general surgical population [17,40,41]. The incidence of difficult or failed intubation is much less. Individual bedside tests have only poor to moderate discriminative power in predicting difficult intubation for patients with no airway pathology [28,42-47].

Most commonly, difficult laryngoscopy is defined as a Cormack-Lehane class 3 or 4 view, in which the vocal cords cannot be seen during laryngoscopy (figure 2). Difficult intubation is defined as difficulty or inability placing a tracheal tube into the larynx and trachea.

Common risk factors for difficult intubation include (table 6) [17,41] (see 'Airway examination' above):

Prior difficult intubation

Small mouth opening (<3 finger breadths)

Mallampati class 3 or 4 (figure 1)

Shortened TMD (<6 cm)

Shortened sternomental distance (<12 cm)

Limited neck mobility

Limited mandibular protrusion or upper lip bite test (ULBT) grade 3

Thick neck (circumference >40 cm)

Predictors of difficult laryngoscopy and intubation may be less useful or irrelevant when video laryngoscopes (VL) are used. VLs improve laryngeal view in most patients [48]. Their use achieves a high success rate for intubation of patients with predicted difficult intubation, and those who have failed direct laryngoscopy [49,50]. In a study of over 2000 VL intubations, Mallampati score did not correlate with failed intubation [51]. The strongest predictor of failure was neck pathology, including presence of a surgical scar, radiation changes, or mass. In another study, risk factors for difficult VL intubation after direct laryngoscopy were Cormack-Lehane grade 3 or 4 view with direct laryngoscopy (figure 2), short sternothyroid distance, and high upper lip bite test score (table 7) [52].

Obesity as a risk factor — Obesity is a recognized risk factor for difficulty with airway management [40,41]. An audit of major complications of airway management from over three million anesthetics in the United Kingdom found twice as many case reports of major complications in patients with obesity, especially with severe obesity [53]. Among patients with obesity, there was an increased frequency of aspiration and other complications with the use of supraglottic airways, difficulty with intubation, and airway obstruction during emergence or recovery from anesthesia. When rescue devices were required, they failed more often than in patients with normal body weight. (See "Anesthesia for the patient with obesity", section on 'Airway management'.)

Difficult mask ventilation is more common in patients with obesity, particularly in those with obstructive sleep apnea [30,31]. It is less clear whether obesity increases the risk of difficult laryngoscopy or intubation. Some studies suggest that obesity is a risk factor for both difficult mask ventilation and difficult laryngoscopy, while other studies suggest that with proper positioning and preparation, ventilation and laryngoscopy are not difficult [54-58]. In one large retrospective single center database study, patients with obesity were more difficult to intubate than lean patients, but the degree of obesity had no effect on the odds of difficulty [59]. Among approximately 67,700 patients who required intubation, the odds of difficult intubation (defined as more than one attempt) increased in a linear fashion with increasing BMI up to a BMI of 30 kg/m2, but remained constant for patients with BMI >30 kg/m2.

Distribution of body fat varies among patients with obesity, even at similar body mass index, which may account for some of the variability in difficulty with airway management. Oxygen saturation typically falls more quickly with apnea in patients with obesity, so adequate preoxygenation is particularly important in these patients. (See 'Preoxygenation' below.)

Physiologically difficult airway — The term "physiologically difficult airway" refers to the patient with physiologic derangements that increase the risk of hypotension, hypoxemia, arrhythmias, and potential cardiac arrest during and after intubation and/or conversion to positive pressure ventilation. These events are most common in critically ill patients or in patients with severe cardiac or pulmonary disease.

The potential for physiologic adverse events should be recognized prior to induction of anesthesia and airway management, and should inform the choice of induction agents and preoxygenation/apneic oxygenation, as well as the intubation strategy [60]. These issues are discussed in multiple other topics, including the following:

(See "Complications of airway management in adults", section on 'Physiologic complications related to airway management'.)

(See "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

(See "General anesthesia: Intravenous induction agents".)

CREATION OF A STRATEGY FOR AIRWAY MANAGEMENT

General approach — The airway management plan will depend on the medical history of the patient, the type of procedure for which anesthesia is being given, the surgical conditions required, and the expected degree of difficulty should intubation be necessary. It is important to recognize that any strategy can unexpectedly fail, and backup plans should always be considered. The American Society of Anesthesiologists Difficult Airway Algorithm and associated infographics are tools for organizing the approach to the patient with a potentially difficult airway and the management of unexpected airway problems (algorithm 1 and figure 3) [61]. Anesthesia clinicians should be familiar with the difficult airway algorithm. (See "Management of the difficult airway for general anesthesia in adults", section on 'Importance of an algorithmic approach'.)

Difficult airway management in patients with trauma is discussed separately, and is shown in an algorithm (algorithm 2). (See "Anesthesia for adult trauma patients", section on 'Airway management'.)

The following questions should be considered when formulating an airway management plan:

What airway devices can be used for patients undergoing this procedure? The choice of airway device may be impacted by the location and expected length of the surgical procedure, patient position during surgery, and the need for muscle relaxants. (See 'Choice of airway device' below.)

What airway devices can be used in this patient? This must take into account the risk of aspiration, difficult mask ventilation, difficult supraglottic airway (SGA) placement, or difficult intubation, as well as the likelihood of difficult ventilation (high PIP, need for PEEP) once the airway is placed.

If intubation is planned, what method should be used (direct laryngoscopy, video laryngoscopy, or flexible bronchoscopic intubation)? Direct laryngoscopy is appropriate for most patients, though video laryngoscopy is becoming more common. (See 'Choice of intubation technique' below.)

Should induction of general anesthesia occur before or after intubation (asleep versus awake intubation)? If a difficult intubation is expected, the decision to intubate awake depends upon expected difficulty with mask ventilation or intubation as well as the potential risk of aspiration or rapid desaturation (algorithm 1 and figure 3).

Should spontaneous ventilation be maintained?

Is a surgical airway needed? If so, should the surgeon be standing by or should a tracheostomy be performed while the patient is awake?

If the initial plan fails, what is plan B (the backup plan)? The equipment and expertise needed for plan B should be arranged ahead of time.

Management of the difficult airway during induction of anesthesia is discussed more fully elsewhere. (See "Approach to the difficult airway in adults for emergency medicine and critical care" and "Management of the difficult airway for general anesthesia in adults".)

Choice of airway device

Airway device options — Not all patients undergoing general anesthesia require the placement of an endotracheal tube. Supraglottic airway devices (SGAs) are rapidly becoming more widespread in use as an alternative to an endotracheal tube, especially in Europe.

In a review of approximately three million anesthetics in the United Kingdom, an SGA was used for airway management in 56.2 percent of cases, while an endotracheal tube was used in 38.4 percent, and 5.3 percent were managed with mask ventilation alone [53].

Technique for use and the various types of airway management devices are discussed more fully elsewhere. (See "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults" and "Direct laryngoscopy and endotracheal intubation in adults" and "Video laryngoscopes and optical stylets for airway management for anesthesia in adults" and "Flexible scope intubation for anesthesia".)

Facemask – Facemask ventilation is the most basic of airway management techniques. Ventilation by facemask is used most often in the operating room between induction of anesthesia and placement of an airway device. Airway management with facemask alone may be used for short cases without the surgical need for muscle relaxation if the anesthesia clinician will have full access to the patient's airway throughout the case. (See "Basic airway management in adults", section on 'Bag-mask ventilation'.)

Supraglottic airway (SGA) – SGA is a term used to describe any airway device that is inserted into the oropharynx and has a ventilation orifice above the glottis. The most common type of SGA is the laryngeal mask airway (LMA), although there are others. An SGA may be used as the planned airway management device (with either spontaneous or controlled ventilation), as a conduit for intubation, or as a rescue device when either mask ventilation or intubation are difficult. (See "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults".)

Endotracheal tube (ETT) – The ETT is a single use device which is inserted through the nose or mouth with the distal end in the mid-trachea. For adults and most pediatric patients beyond the newborn period, a tube with an inflatable cuff is used to protect against secretions and to create a seal for positive pressure ventilation. For some specific surgical procedures, specialized endotracheal tubes may be necessary, such as a laser-safe tube for airway laser surgery, or a double-lumen tube for lung isolation for differential ventilation. (See "Direct laryngoscopy and endotracheal intubation in adults" and "Lung isolation techniques", section on 'Double-lumen endobronchial tubes' and "Anesthesia for head and neck surgery", section on 'Surgical considerations'.)

Supraglottic airway versus endotracheal tube — The decision to use a supraglottic airway (SGA) or an endotracheal tube (ETT) must take into account comorbidities and findings on the preoperative airway assessment, in addition to the type and expected length of the surgical procedure. In addition, the following device-specific factors may affect the decision to choose one or the other class of airway device:

Clinically important features of SGA use:

Easily placed blindly

Less hemodynamic response to placement than laryngoscopy and ETT placement

Lower risk of bronchospasm

Lower peak inspiratory pressures possible

Does not protect against aspiration

Does not protect against laryngospasm

Clinically important features of ETT use:

May be difficult to place

Requires deeper level of anesthesia for placement than SGA

Stimulus for bronchospasm

High peak inspiratory pressures possible

Protects against aspiration

In general, we use SGA for shorter procedures (<3 hours), for patients who are at low risk of aspiration, and for procedures which will not require a prolonged period of muscle relaxation. The use of SGA for laparoscopy is controversial because of the potential risk of aspiration and inability to ventilate with increased intraabdominal pressure, but there are several studies and case reports describing the safe use of an SGA for laparoscopic procedures [62,63]. SGA devices can be used in the prone position for selected patients having short procedures, such as minor rectal surgeries [64]. (See "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults".)

Choice of intubation technique — The choice of intubation technique should be individualized based on the expertise of the clinician, the availability of airway devices, and the clinical situation. Use of a familiar technique by an experienced clinician is most likely to succeed.

A direct laryngoscope is used to create a view of the glottis with direct line of sight; direct laryngoscopy (DL) has been the most commonly used method for intubation. Increasingly, practice is shifting toward the use of indirect laryngoscopy with a video laryngoscope (VL) for intubation. Some UpToDate contributors and some airway guidelines recommend using VL for the first attempt for intubation whenever possible [65,66]. We use VL selectively, based on the expected difficulty with intubation, the clinical situation, and availability of the equipment.

For patients with anticipated difficult airway management, we suggest using an advanced airway management technique (eg, video laryngoscopy, flexible scope intubation) rather than direct laryngoscopy for the first attempt at intubation. Use of VL is well established for patients for whom direct laryngoscopy may be difficult. Video laryngoscopy has many advantages, especially in patients with a known or suspected difficult airway, such as improved glottic view, increased first pass success, and the advantage of a video screen for teaching trainees or guiding the operator. However, VL has been associated with longer times to intubation and risk of oropharyngeal injury. The comparison between DL and VL is discussed in detail separately. (See "Video laryngoscopes and optical stylets for airway management for anesthesia in adults", section on 'VL versus DL'.)

Clinicians should be proficient in the use of a variety of devices even if VL is chosen as a preferred technique. Whatever primary device the clinician chooses, it is important to have an alternate device and technique available should that primary device fail [67].

For patients who require awake intubation, a flexible intubating scope is commonly used. Other techniques, including video laryngoscopy, can be used for awake intubation as well. (See "Flexible scope intubation for anesthesia" and "Awake tracheal intubation".)

Choice of medications for induction and intubation — Plans for airway management and the choice of anesthesia induction agents are interdependent. Induction must achieve a level of anesthesia deep enough to allow successful placement of the chosen airway device without physiologic response (eg, hypertension, tachycardia, cough). Endotracheal intubation requires a deeper level of anesthesia than supraglottic airway placement. In most cases, a combination of medications is used. Intravenous induction is most common; inhalation induction is occasionally used in adult patients. (See "Induction of general anesthesia: Overview".)

Patients who have not fasted or are at high risk for aspiration should undergo rapid sequence induction. (See "Rapid sequence induction and intubation (RSII) for anesthesia".)

Intravenous induction — The most common induction agents used to achieve unconsciousness and apnea are propofol, ketamine, and etomidate. Methohexital (1 to 2 mg/kg IV), a short-acting barbiturate, may be used in selected circumstances (eg, patients with egg allergy, for anesthesia for electroconvulsive therapy). Thiopental, once the most common anesthesia induction agent, is no longer available in the United States. In many cases, a combination of medications is used when placement of an airway device is planned, so that less of each individual agent is necessary.

The selection of intravenous induction agents, opioids, and neuromuscular blocking agents during induction of anesthesia, as well as adjuvant medications, are discussed separately. (See "General anesthesia: Intravenous induction agents".)

Inhalation induction — Induction of anesthesia can be performed with inhalation of a volatile anesthetic. This technique is commonly used in pediatric patients to avoid needle placement for intravenous (IV) induction. It is rarely used in adults; though, it is useful in cases with difficult IV access or when maintenance of spontaneous ventilation is preferred. (See "Induction of general anesthesia: Overview", section on 'Inhalation anesthetic induction'.)

SECURING THE AIRWAY — Once the plan for induction and airway management is established and a backup plan determined, the patient is positioned and preoxygenated.

Preparation for induction of anesthesia — Prior to induction of anesthesia, an assortment of standard and alternative airway devices should be immediately available, including small, medium, and large facemasks; several sizes and types of laryngoscopes; oral and nasal airways; several sizes of supraglottic airway, and a bougie. Alternative devices for laryngoscopy, including a video laryngoscope and flexible intubating scope, as well as other emergency airway equipment should be accessible quickly, and present in the operating room or anesthetizing location if difficult airway is suspected (table 8). (See 'Prediction of the difficult airway' above.)

Patient positioning — Before induction of anesthesia, the patient's head should be placed in the sniffing position (atlanto-occipital extension with head elevation of 3 to 7 cm), supported so that the neck is flexed and the head extended. Though this may not be the optimal final position for airway management in a specific patient, it should be the starting point, with modification made as necessary. Patients with obesity may require a ramped position to open the space between the chin and the chest, and to align the sternal notch with the external auditory meatus (figure 4) [54].

Preoxygenation — All patients presenting for general anesthesia should be preoxygenated with 100 percent oxygen to increase oxygen reserve and provide additional time to secure the airway. Oxygenation should be maximized throughout airway management, especially for patients at higher risk of desaturation or difficult intubation. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

Since the supine position reduces functional residual capacity (FRC), preoxygenation can be performed in the semi-upright position and is especially useful for those with characteristics associated with oxygenation difficulty (eg, the patient with obesity, the pregnant patient, patients with poor pulmonary reserve) [68].

Preoxygenation is administered for three minutes of normal tidal volume breathing, for eight deep breaths over one minute, or until the fraction of expired oxygen is over 90 percent [69]. Ultimately, the time to desaturation with apnea will depend on the length of preoxygenation as well as the patient's oxygen consumption and FRC. Desaturation may occur more quickly with apnea despite adequate preoxygenation in patients with poor pulmonary reserve (eg, those with COPD, pulmonary hypertension, severe asthma, lung cancer, obesity, obstructive sleep apnea) or increased oxygen consumption (eg, pregnancy).

For patients with predicted difficult intubation, we suggest administration of oxygen by nasal cannula at 10 L/minute in addition to facemask oxygen. The use of nasal cannula for passive apneic oxygenation during laryngoscopy can prolong the time to desaturation in high-risk patients during airway management [70-73]. (See 'Difficult intubation' above.)

Perioxygenation (oxygen delivery throughout airway management) and apneic oxygen techniques can be useful to delay desaturation during apnea time in patients with poor pulmonary reserve or a predicted difficult intubation [60]. Preoxygenation and apneic oxygenation, including the use of humidified high flow oxygen for these techniques, are discussed in detail separately. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

Mask ventilation — After preoxygenation and induction of anesthesia, if a rapid sequence intubation is not planned, mask ventilation should be established using 100 percent oxygen. We close and cover the patient's eyes with tape or a transparent dressing as soon as the patient is unconscious to avoid injury during airway manipulation. Technical aspects of mask ventilation are discussed elsewhere. (See "Basic airway management in adults", section on 'Bag-mask ventilation'.)

Administration of neuromuscular blocking agents — When endotracheal intubation is planned after induction of anesthesia, a neuromuscular blocking agent (NMBA) is routinely administered during induction, to improve intubating conditions and reduce the risk of upper airway injury [74]. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Endotracheal intubation'.)

Timing of administration — Mask ventilation is often established prior to the administration of neuromuscular blocking agents (NMBAs). This sequence allows the clinician to prove his or her ability to ventilate the patient before removing the patient's ability to ventilate on his or her own, while maintaining the option to awaken the patient should attempts at airway control fail.

The need to withhold NMBAs until mask ventilation is established has been questioned, partly because muscle relaxation may improve mask ventilation [75-79]. Administration of an NMBA along with induction agents may also shorten the time to endotracheal intubation. In a randomized trial that compared administration of rocuronium immediately after administration of propofol with administration after checking mask ventilation in 114 patients with normal airways, the mean time to intubation was shorter in patients who received NMBA early (116 versus 195 seconds) [78]. In addition, average tidal volume during mask ventilation was greater in patients who received rocuronium early (550 versus 390 mL per breath).

However, muscle relaxation can make mask ventilation worse or impossible in some patients. Assessment of the ability to mask ventilate prior to administration of NMBA may allow for a change in plan; for example, the use of succinylcholine rather than a longer acting NMBA if mask ventilation is a struggle, or awakening the patient if possible. Thus, the timing of NMBA administration should be individualized based on the expected difficulty with airway management, unless a rapid sequence intubation is being performed. For rapid sequence induction and intubation, the NMBA is typically administered at the same time as the induction agent, without mask ventilation. (See "Rapid sequence induction and intubation (RSII) for anesthesia".)

For patients with anticipated difficulty with mask ventilation or intubation, it is reasonable to withhold the administration of a muscle relaxant until after mask ventilation is confirmed, or consider an awake technique or inhalational induction. If difficulty with airway management is not anticipated, it is reasonable to administer a muscle relaxant prior to confirming mask ventilation. (See "Management of the difficult airway for general anesthesia in adults", section on 'Timing of administration'.)

Choice of neuromuscular blocking agent — The selection of the appropriate NMBA depends on the clinical application and patient factors. Doses and characteristics of commonly used NMBAs are shown in a table (table 9). Selection of NMBA is discussed in detail separately. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Selection of neuromuscular blocking agents'.)

Rocuronium can be relatively quickly reversed with sugammadex if necessary during surgery, or in cases of unexpected difficulty with airway management. However, rapid reversal of neuromuscular block should not be relied upon as a rescue strategy in a possible or actual cannot intubate, cannot ventilate scenario. Sugammadex can reverse an intubating dose of rocuronium more rapidly than an intubating dose of succinylcholine would resolve, but reversal may still take up to six minutes [80]. The primary factors that determine return of spontaneous ventilation after induction of anesthesia are the depth of anesthesia and respiratory depression from the induction agents, not the reversal of neuromuscular blockade [81]. In the event of a cannot intubate, cannot ventilate scenario, efforts should focus on restoring oxygenation and ventilation.

Reversal of NMBAs is discussed in detail separately. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Sugammadex' and "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Reversal of neuromuscular block'.)

Airway placement — Techniques for placement of supraglottic airway (SGA) and endotracheal intubation, flexible scope intubation, and rapid sequence induction are discussed separately. (See "Flexible scope intubation for anesthesia" and "Direct laryngoscopy and endotracheal intubation in adults".)

If the use of a SGA is planned, after flaccidity is achieved, as assessed by masseter muscle tone (ie, laxity of the jaw with no resistance to mouth opening), the clinician can proceed with SGA placement.

Laryngoscopy is performed once a deep enough level of anesthesia has been achieved and, in most cases, when the muscle relaxant is fully effective. There is significant variation in the time to maximal muscle relaxation with different agents. For routine induction, relaxation with succinylcholine (1 mg/kg IV) occurs in 45 to 60 seconds, and after approximately three minutes for an intubating dose of rocuronium (0.45 to 0.6 mg/kg IV), vecuronium (0.08 to 0.1 mg/kg IV), or cisatracurium (0.15 to 0.2 mg/kg IV) (table 9).

A peripheral nerve stimulator can be used to assess paralysis during induction and throughout the anesthetic. The stimulating electrodes are placed on the skin along the path of a peripheral nerve, most commonly the ulnar nerve at the wrist. The device applies a sequence of four electrical stimuli over two seconds, and the contraction of the innervated muscle is monitored. As paralysis deepens after administration of a muscle relaxant, the twitches fade and ultimately disappear. For optimal intubating conditions, the twitches should be obliterated. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Endotracheal intubation' and "Monitoring neuromuscular blockade", section on 'Train-of-four'.)

If a twitch monitor is not used, laryngoscopy is performed at approximately three minutes after induction, or when a significant improvement in compliance with mask ventilation is felt as a sign of paralysis.

Confirmation of airway placement — Once an airway device is placed, correct placement must be confirmed with the following:

Effective manual ventilation.

Symmetrical chest rise.

Visible condensation in mask or tube of airway device.

End-tidal CO2 waveform on gas analyzer.

If endotracheal tube placed, right mainstem bronchus intubation and esophageal intubation must be ruled out with bilateral breath sounds and lack of sounds of air entry into stomach, and CO2 wave form detection. Especially in thin patients, air entry into the stomach may be heard in the chest and mistaken for breath sounds. Confirmation of correct endotracheal tube placement is discussed separately. (See "Direct laryngoscopy and endotracheal intubation in adults", section on 'Confirming proper tracheal tube placement'.)

Ultrasound can also be used to confirm endotracheal tube placement. A probe placed over the lateral intercostal spaces bilaterally will detect movement of the pleura against the lung if ventilation is present ("lung sliding sign") [20].

If an SGA is used, air leak should occur at high enough peak pressure to allow adequate tidal volume, 18 to 20 cm H2O.

If confirmation is not possible, the airway device should be adjusted or replaced.

EXTUBATION — Any patient who was at particular risk for difficult airway management at the beginning of anesthesia should be considered at risk for airway compromise at the end of the anesthetic, and a plan should be in place for safe extubation. Risk stratification for difficult extubation, creation of a strategy for extubation, and management of extubation are discussed in detail separately. (See "Extubation following anesthesia".)

AIRWAY MANAGEMENT FOR PATIENTS WITH COVID-19 — In patients with novel coronavirus disease 2019 (COVID-19 or nCoV), there may be high risk of spread of the virus during airway management. Procedures designed to minimize infectious risk to care providers and spread of the virus are discussed separately. (See "Overview of infection control during anesthetic care", section on 'Airway management'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Airway management in adults" and "Society guideline links: COVID-19 – Index of guideline topics".)

SUMMARY AND RECOMMENDATIONS

Airway assessment

Preoperative airway assessment should include review of outcomes with prior anesthetics, and assessment of mouth opening and dentition, Mallampati class (figure 1), thyromental distance (TMD), neck range of motion, and mandibular protrusion. (See 'Airway assessment' above.)

Some disease states, bedside airway examination tests, and patient characteristics may predict anatomic or physiologic difficulty with airway management (table 3). (See 'Prediction of the difficult airway' above.)

Airway management strategy

The strategy for airway management for general anesthesia depends on the requirements for the planned surgical or diagnostic procedure, patient characteristics that affect airway management, predicted degree of difficulty with airway management, and risk of aspiration or rapid desaturation (algorithm 1 and figure 3). (See 'Creation of a strategy for airway management' above.)

The primary plan must determine the preferred airway device and intubation technique. There should always be a backup plan, with the equipment and expertise readily available to implement an emergency airway algorithm (algorithm 1). (See 'General approach' above.)

Choice of airway device

The choice between endotracheal tube (ETT) placement and the use of a supraglottic airway (SGA) depends upon both patient and surgical factors. (See 'Choice of airway device' above.)

In general, we use SGA for shorter procedures (<3 hours), for patients who are at low risk of aspiration, and for procedures which will not require a prolonged period of muscle relaxation.

ETT is preferred in patients at high risk for aspiration, those that require high inspiratory pressures, and for longer cases requiring muscle relaxation.

Airway management with facemask alone may be used for short cases without the surgical need for muscle relaxation if the anesthesia clinician will have full access to the patient's airway throughout the case.

Choice of intubation technique

The choice of intubation technique should be individualized based on the expertise of the clinician, the availability of airway devices, and the clinical situation. Use of a familiar technique by an experienced clinician is most likely to succeed. Some UpToDate contributors and some airway guidelines recommend using VL for first attempt at intubation whenever possible.

For patients with anticipated difficult airway management, we suggest using an advanced airway management technique (eg, videolaryngoscopy, flexible scope intubation) rather than direct laryngoscopy for the first attempt at intubation (Grade 2C). (See 'Choice of intubation technique' above and "Video laryngoscopes and optical stylets for airway management for anesthesia in adults", section on 'VL versus DL'.)

For patients who require awake intubation, a flexible intubating scope is commonly used. Other strategies (eg, video laryngoscopy) can be used as well. (See "Awake tracheal intubation".)

Whatever primary device is used, it is important to have an alternate device and technique available should that primary device fail. (See 'Choice of intubation technique' above.)

Induction medications – A combination of medications is usually used to achieve the depth of anesthesia necessary for induction of anesthesia and airway management. Endotracheal intubation requires a deeper level of anesthesia than supraglottic airway placement. (See 'Choice of medications for induction and intubation' above.)

Positioning and perioxygenation The patient should be positioned for optimal airway management (eg, "sniffing position" with ramp, if necessary) and preoxygenated with 100 percent oxygen delivered by mask for three minutes of normal tidal volume breathing, for eight deep breaths over one minute, or until the fraction of expired oxygen is over 90 percent. Maximize oxygen delivery throughout airway management. For patients with predicted difficult intubation or increased risk of desaturation, we suggest a perioxygenation technique (eg, administration of oxygen by nasal cannula at 10 L/minute) in addition to facemask oxygen, to provide apneic oxygenation and prolong the time to desaturation during apnea (Grade 2C). (See 'Preparation for induction of anesthesia' above and "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

Timing of neuromuscular blocking agents (NMBAs) – Other than for rapid sequence induction and intubation, the timing of administration of NMBAs relative to establishing mask ventilation should be individualized, based on the expected difficulty with airway management. For patients with anticipated difficulty with mask ventilation or intubation, it is reasonable to withhold administration of an NMBA until after mask ventilation is confirmed, or consider an awake or inhalation induction. For patients without anticipated difficulty with mask ventilation or intubation, it is reasonable to administer NMBAs prior to proving the ability to ventilate by mask. (See 'Administration of neuromuscular blocking agents' above.)

Confirmation of correct airway device placement – After placement of an airway device, proper position must be confirmed by auscultation of the chest and the presence of an end-tidal CO2 waveform. If confirmation is not possible, the airway device should be adjusted or replaced. (See 'Confirmation of airway placement' above and "Direct laryngoscopy and endotracheal intubation in adults", section on 'Confirming proper tracheal tube placement'.)

Extubation – Any patient who was at particular risk for difficult airway management at the beginning of anesthesia should be considered at risk for airway compromise at the end of the anesthetic. Airway management should include a plan for safe emergence and extubation. (See "Extubation following anesthesia".)

  1. Rosenblatt WH, Sukhupragarn W. Airway management. In: Clinical Anesthesia, 6th ed, Barash PG, Cullen BF, Stoelting RK, et al (Eds), Lippincott, Williams and Wilkins, Philadelphia 2009. p.751.
  2. Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can Anaesth Soc J 1985; 32:429.
  3. Samsoon GL, Young JR. Difficult tracheal intubation: a retrospective study. Anaesthesia 1987; 42:487.
  4. Lee A, Fan LT, Gin T, et al. A systematic review (meta-analysis) of the accuracy of the Mallampati tests to predict the difficult airway. Anesth Analg 2006; 102:1867.
  5. Ezri T, Warters RD, Szmuk P, et al. The incidence of class "zero" airway and the impact of Mallampati score, age, sex, and body mass index on prediction of laryngoscopy grade. Anesth Analg 2001; 93:1073.
  6. Singhal V, Sharma M, Prabhakar H, et al. Effect of posture on mouth opening and modified Mallampati classification for airway assessment. J Anesth 2009; 23:463.
  7. Amadasun FE, Adudu OP, Sadiq A. Effects of position and phonation on oropharyngeal view and correlation with laryngoscpic view. Niger J Clin Pract 2010; 13:417.
  8. Tham EJ, Gildersleve CD, Sanders LD, et al. Effects of posture, phonation and observer on Mallampati classification. Br J Anaesth 1992; 68:32.
  9. Khan ZH, Eskandari S, Yekaninejad MS. A comparison of the Mallampati test in supine and upright positions with and without phonation in predicting difficult laryngoscopy and intubation: A prospective study. J Anaesthesiol Clin Pharmacol 2015; 31:207.
  10. Hanouz JL, Bonnet V, Buléon C, et al. Comparison of the Mallampati Classification in Sitting and Supine Position to Predict Difficult Tracheal Intubation: A Prospective Observational Cohort Study. Anesth Analg 2018; 126:161.
  11. Butler PJ, Dhara SS. Prediction of difficult laryngoscopy: an assessment of the thyromental distance and Mallampati predictive tests. Anaesth Intensive Care 1992; 20:139.
  12. Janssens M, Hartstein G. Management of difficult intubation. Eur J Anaesthesiol 2001; 18:3.
  13. Qudaisat IY, Al-Ghanem SM. Short thyromental distance is a surrogate for inadequate head extension, rather than small submandibular space, when indicating possible difficult direct laryngoscopy. Eur J Anaesthesiol 2011; 28:600.
  14. Mashour GA, Stallmer ML, Kheterpal S, Shanks A. Predictors of difficult intubation in patients with cervical spine limitations. J Neurosurg Anesthesiol 2008; 20:110.
  15. Eberhart LH, Arndt C, Cierpka T, et al. The reliability and validity of the upper lip bite test compared with the Mallampati classification to predict difficult laryngoscopy: an external prospective evaluation. Anesth Analg 2005; 101:284.
  16. Khan ZH, Mohammadi M, Rasouli MR, et al. The diagnostic value of the upper lip bite test combined with sternomental distance, thyromental distance, and interincisor distance for prediction of easy laryngoscopy and intubation: a prospective study. Anesth Analg 2009; 109:822.
  17. Shiga T, Wajima Z, Inoue T, Sakamoto A. Predicting difficult intubation in apparently normal patients: a meta-analysis of bedside screening test performance. Anesthesiology 2005; 103:429.
  18. Rosenblatt W, Ianus AI, Sukhupragarn W, et al. Preoperative endoscopic airway examination (PEAE) provides superior airway information and may reduce the use of unnecessary awake intubation. Anesth Analg 2011; 112:602.
  19. Kristensen MS. Ultrasonography in the management of the airway. Acta Anaesthesiol Scand 2011; 55:1155.
  20. Kristensen MS, Teoh WH, Graumann O, Laursen CB. Ultrasonography for clinical decision-making and intervention in airway management: from the mouth to the lungs and pleurae. Insights Imaging 2014; 5:253.
  21. You-Ten KE, Siddiqui N, Teoh WH, Kristensen MS. Point-of-care ultrasound (POCUS) of the upper airway. Can J Anaesth 2018; 65:473.
  22. Carsetti A, Sorbello M, Adrario E, et al. Airway Ultrasound as Predictor of Difficult Direct Laryngoscopy: A Systematic Review and Meta-analysis. Anesth Analg 2022; 134:740.
  23. Benavides-Zora D, Jaramillo MC, Townsley MM, et al. Diagnostic Performance of Airway Ultrasound for the Assessment of Difficult Laryngoscopy: A Systematic Review and Meta-Analysis. J Cardiothorac Vasc Anesth 2023; 37:1101.
  24. Giordano G, Alessandri F, Zulian A, et al. Pre-operative ultrasound prediction of difficult airway management in adult patients: A systematic review of clinical evidence. Eur J Anaesthesiol 2023; 40:313.
  25. Nørskov AK, Rosenstock CV, Wetterslev J, et al. Diagnostic accuracy of anaesthesiologists' prediction of difficult airway management in daily clinical practice: a cohort study of 188 064 patients registered in the Danish Anaesthesia Database. Anaesthesia 2015; 70:272.
  26. Sajayan A, Nair A, McNarry AF, et al. Analysis of a national difficult airway database. Anaesthesia 2022; 77:1081.
  27. Roth D, Pace NL, Lee A, et al. Airway physical examination tests for detection of difficult airway management in apparently normal adult patients. Cochrane Database Syst Rev 2018; 5:CD008874.
  28. Detsky ME, Jivraj N, Adhikari NK, et al. Will This Patient Be Difficult to Intubate?: The Rational Clinical Examination Systematic Review. JAMA 2019; 321:493.
  29. Roth D, Pace NL, Lee A, et al. Bedside tests for predicting difficult airways: an abridged Cochrane diagnostic test accuracy systematic review. Anaesthesia 2019; 74:915.
  30. Langeron O, Masso E, Huraux C, et al. Prediction of difficult mask ventilation. Anesthesiology 2000; 92:1229.
  31. Kheterpal S, Han R, Tremper KK, et al. Incidence and predictors of difficult and impossible mask ventilation. Anesthesiology 2006; 105:885.
  32. Yildiz TS, Solak M, Toker K. The incidence and risk factors of difficult mask ventilation. J Anesth 2005; 19:7.
  33. Lundstrøm LH, Rosenstock CV, Wetterslev J, Nørskov AK. The DIFFMASK score for predicting difficult facemask ventilation: a cohort study of 46,804 patients. Anaesthesia 2019; 74:1267.
  34. Kheterpal S, Martin L, Shanks AM, Tremper KK. Prediction and outcomes of impossible mask ventilation: a review of 50,000 anesthetics. Anesthesiology 2009; 110:891.
  35. Kheterpal S, Healy D, Aziz MF, et al. Incidence, predictors, and outcome of difficult mask ventilation combined with difficult laryngoscopy: a report from the multicenter perioperative outcomes group. Anesthesiology 2013; 119:1360.
  36. Verghese C, Brimacombe JR. Survey of laryngeal mask airway usage in 11,910 patients: safety and efficacy for conventional and nonconventional usage. Anesth Analg 1996; 82:129.
  37. Ramachandran SK, Mathis MR, Tremper KK, et al. Predictors and clinical outcomes from failed Laryngeal Mask Airway Unique™: a study of 15,795 patients. Anesthesiology 2012; 116:1217.
  38. Law JA, Broemling N, Cooper RM, et al. The difficult airway with recommendations for management--part 2--the anticipated difficult airway. Can J Anaesth 2013; 60:1119.
  39. Hartsuyker P, Kanczuk ME, Lawn D, et al. The effect of class 3 obesity on the functionality of supraglottic airway devices: a historical cohort analysis with propensity score matching. Can J Anaesth 2023; 70:1744.
  40. Lundstrøm LH, Møller AM, Rosenstock C, et al. High body mass index is a weak predictor for difficult and failed tracheal intubation: a cohort study of 91,332 consecutive patients scheduled for direct laryngoscopy registered in the Danish Anesthesia Database. Anesthesiology 2009; 110:266.
  41. Heinrich S, Birkholz T, Irouschek A, et al. Incidences and predictors of difficult laryngoscopy in adult patients undergoing general anesthesia : a single-center analysis of 102,305 cases. J Anesth 2013; 27:815.
  42. el-Ganzouri AR, McCarthy RJ, Tuman KJ, et al. Preoperative airway assessment: predictive value of a multivariate risk index. Anesth Analg 1996; 82:1197.
  43. Rose DK, Cohen MM. The incidence of airway problems depends on the definition used. Can J Anaesth 1996; 43:30.
  44. Cook TM, MacDougall-Davis SR. Complications and failure of airway management. Br J Anaesth 2012; 109 Suppl 1:i68.
  45. Rose DK, Cohen MM. The airway: problems and predictions in 18,500 patients. Can J Anaesth 1994; 41:372.
  46. Nath G, Sekar M. Predicting difficult intubation--a comprehensive scoring system. Anaesth Intensive Care 1997; 25:482.
  47. Wilson ME, Spiegelhalter D, Robertson JA, Lesser P. Predicting difficult intubation. Br J Anaesth 1988; 61:211.
  48. Sun DA, Warriner CB, Parsons DG, et al. The GlideScope Video Laryngoscope: randomized clinical trial in 200 patients. Br J Anaesth 2005; 94:381.
  49. Jayaraj AK, Siddiqui N, Abdelghany SMO, Balki M. Management of difficult and failed intubation in the general surgical population: a historical cohort study in a tertiary care centre. Can J Anaesth 2022; 69:427.
  50. Aziz MF, Brambrink AM, Healy DW, et al. Success of Intubation Rescue Techniques after Failed Direct Laryngoscopy in Adults: A Retrospective Comparative Analysis from the Multicenter Perioperative Outcomes Group. Anesthesiology 2016; 125:656.
  51. Aziz MF, Healy D, Kheterpal S, et al. Routine clinical practice effectiveness of the Glidescope in difficult airway management: an analysis of 2,004 Glidescope intubations, complications, and failures from two institutions. Anesthesiology 2011; 114:34.
  52. Tremblay MH, Williams S, Robitaille A, Drolet P. Poor visualization during direct laryngoscopy and high upper lip bite test score are predictors of difficult intubation with the GlideScope videolaryngoscope. Anesth Analg 2008; 106:1495.
  53. http://www.rcoa.ac.uk/nap4 (Accessed on November 10, 2014).
  54. Collins JS, Lemmens HJ, Brodsky JB, et al. Laryngoscopy and morbid obesity: a comparison of the "sniff" and "ramped" positions. Obes Surg 2004; 14:1171.
  55. Juvin P, Lavaut E, Dupont H, et al. Difficult tracheal intubation is more common in obese than in lean patients. Anesth Analg 2003; 97:595.
  56. Lavi R, Segal D, Ziser A. Predicting difficult airways using the intubation difficulty scale: a study comparing obese and non-obese patients. J Clin Anesth 2009; 21:264.
  57. Hekiert AM, Mandel J, Mirza N. Laryngoscopies in the obese: predicting problems and optimizing visualization. Ann Otol Rhinol Laryngol 2007; 116:312.
  58. Brodsky JB, Lemmens HJ, Brock-Utne JG, et al. Morbid obesity and tracheal intubation. Anesth Analg 2002; 94:732.
  59. Saasouh W, Laffey K, Turan A, et al. Degree of obesity is not associated with more than one intubation attempt: a large centre experience. Br J Anaesth 2018; 120:1110.
  60. Kornas RL, Owyang CG, Sakles JC, et al. Evaluation and Management of the Physiologically Difficult Airway: Consensus Recommendations From Society for Airway Management. Anesth Analg 2021; 132:395.
  61. Apfelbaum JL, Hagberg CA, Connis RT, et al. 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway. Anesthesiology 2022; 136:31.
  62. Viira D, Myles PS. The use of the laryngeal mask in gynaecological laparoscopy. Anaesth Intensive Care 2004; 32:560.
  63. Saraswat N, Kumar A, Mishra A, et al. The comparison of Proseal laryngeal mask airway and endotracheal tube in patients undergoing laparoscopic surgeries under general anaesthesia. Indian J Anaesth 2011; 55:129.
  64. López AM, Valero R, Brimacombe J. Insertion and use of the LMA Supreme in the prone position. Anaesthesia 2010; 65:154.
  65. Law JA, Duggan LV, Asselin M, et al. 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. Can J Anaesth 2021; 68:1405.
  66. Chrimes N, Higgs A, Hagberg CA, et al. Preventing unrecognised oesophageal intubation: a consensus guideline from the Project for Universal Management of Airways and international airway societies. Anaesthesia 2022; 77:1395.
  67. Levitan RM. Video laryngoscopy, regardless of blade shape, still requires a backup plan. Ann Emerg Med 2013; 61:421.
  68. Dixon BJ, Dixon JB, Carden JR, et al. Preoxygenation is more effective in the 25 degrees head-up position than in the supine position in severely obese patients: a randomized controlled study. Anesthesiology 2005; 102:1110.
  69. Tanoubi I, Drolet P, Donati F. Optimizing preoxygenation in adults. Can J Anaesth 2009; 56:449.
  70. Weingart SD, Levitan RM. Preoxygenation and prevention of desaturation during emergency airway management. Ann Emerg Med 2012; 59:165.
  71. Ramachandran SK, Cosnowski A, Shanks A, Turner CR. Apneic oxygenation during prolonged laryngoscopy in obese patients: a randomized, controlled trial of nasal oxygen administration. J Clin Anesth 2010; 22:164.
  72. Taha SK, Siddik-Sayyid SM, El-Khatib MF, et al. Nasopharyngeal oxygen insufflation following pre-oxygenation using the four deep breath technique. Anaesthesia 2006; 61:427.
  73. Sakles JC, Mosier JM, Patanwala AE, et al. First Pass Success Without Hypoxemia Is Increased With the Use of Apneic Oxygenation During Rapid Sequence Intubation in the Emergency Department. Acad Emerg Med 2016; 23:703.
  74. Lundstrøm LH, Duez CHV, Nørskov AK, et al. Effects of avoidance or use of neuromuscular blocking agents on outcomes in tracheal intubation: a Cochrane systematic review. Br J Anaesth 2018; 120:1381.
  75. Ikeda A, Isono S, Sato Y, et al. Effects of muscle relaxants on mask ventilation in anesthetized persons with normal upper airway anatomy. Anesthesiology 2012; 117:487.
  76. Goodwin MW, Pandit JJ, Hames K, et al. The effect of neuromuscular blockade on the efficiency of mask ventilation of the lungs. Anaesthesia 2003; 58:60.
  77. Warters RD, Szabo TA, Spinale FG, et al. The effect of neuromuscular blockade on mask ventilation. Anaesthesia 2011; 66:163.
  78. Min SH, Im H, Kim BR, et al. Randomized Trial Comparing Early and Late Administration of Rocuronium Before and After Checking Mask Ventilation in Patients With Normal Airways. Anesth Analg 2019; 129:380.
  79. Ide A, Nozaki-Taguchi N, Sato S, et al. Rocuronium versus saline for effective facemask ventilation during anesthesia induction: a double-blinded randomized placebo-controlled trial. BMC Anesthesiol 2022; 22:173.
  80. Lee C, Jahr JS, Candiotti KA, et al. Reversal of profound neuromuscular block by sugammadex administered three minutes after rocuronium: a comparison with spontaneous recovery from succinylcholine. Anesthesiology 2009; 110:1020.
  81. Naguib M, Brewer L, LaPierre C, et al. The Myth of Rescue Reversal in "Can't Intubate, Can't Ventilate" Scenarios. Anesth Analg 2016; 123:82.
Topic 91218 Version 65.0

References

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