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Management of the difficult airway for general anesthesia in adults

Management of the difficult airway for general anesthesia in adults
Literature review current through: Jan 2024.
This topic last updated: Sep 21, 2023.

INTRODUCTION — Difficulty with airway management for anesthesia has potentially serious implications, as failure to secure a patent airway can result in hypoxic brain injury or death in a matter of minutes. Early recognition that a patient's airway may be difficult to manage allows the clinician to plan the anesthetic to minimize the potential for serious airway-related morbidity.

In the unanticipated difficult airway, a pre-formulated strategy for airway management may reduce the likelihood of adverse outcomes [1]. Difficulty may occur with facemask ventilation, placement of a supraglottic airway (SGA), laryngoscopy, and/or tracheal intubation. Other significant airway-related complications include aspiration of gastric contents, laryngospasm, and bronchospasm. These airway problems may occur in combination, leading to serious morbidity and mortality [2].

This topic will review patient factors that predict difficult airway management, the development of strategies for the initial management of the predicted difficult airway in the operating room environment, management of the unanticipated difficult airway during induction of general anesthesia, and extubation of the patient with a difficult airway. A general approach to airway management and specific techniques and devices used to manage the airway are discussed separately, as is an approach to the difficult airway during emergency intubation. (See "Airway management for induction of general anesthesia" and "Direct laryngoscopy and endotracheal intubation in adults" and "Approach to the difficult airway in adults for emergency medicine and critical care" and "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults".)

DEFINITIONS — For the purpose of this topic, the difficult airway is defined as the situation in which the anesthesia clinician experiences difficulty with ventilation by mask or supraglottic airway (SGA), difficulty with tracheal intubation, or both. Specifically:

Difficult mask or SGA ventilation – Inability of an unassisted anesthesia clinician to maintain alveolar oxygen delivery or reverse signs of inadequate ventilation

Difficult SGA placement – Requires multiple attempts

Difficult laryngoscopy – Inability to visualize any portion of the vocal cords after multiple attempts

Difficult tracheal intubation – Inability to place a tracheal tube into the larynx and trachea after multiple attempts

RECOGNITION OF THE DIFFICULT AIRWAY — All patients undergoing anesthesia should have a complete history and anesthesia-focused physical examination, including assessment of the airway (table 1) and factors that may influence airway management. One goal of this evaluation is to predict the risk of difficulty with ventilation and intubation. Prediction that a patient will be at risk for difficult mask ventilation, ventilation with a supraglottic airway (SGA), or intubation leads to different airway management strategies, particularly when more than one airway technique is likely to be problematic. The airway history and examination, including factors that predict difficulty with airway management, are discussed more fully separately (see "Airway management for induction of general anesthesia", section on 'Airway assessment'). While these predictive factors are useful for developing an airway management plan, it is important to note that the majority of difficult airways are unanticipated [3].

Difficult mask ventilation – Predictors of difficult mask ventilation include male sex, obstructive sleep apnea, absence of teeth, presence of a beard, and other clinical features (table 2). The degree of difficulty varies and depends on both the number of predictive factors and the skill of the clinician. (See "Airway management for induction of general anesthesia", section on 'Difficult mask ventilation'.)

Difficult SGA ventilation – Factors that predict difficulty ventilating with a SGA include reduced mouth opening; absence of teeth; male sex; obesity; and glottic, hypopharyngeal, and subglottic pathology (table 3). (See "Airway management for induction of general anesthesia", section on 'Difficult supraglottic airway device use'.)

Difficult tracheal intubation – Clinical features that predict difficult intubation are presented in the table (table 4). Those with the highest predictive value for a difficult direct laryngoscopy are a prior history of a difficult intubation, a short thyromental distance, and decreased range of motion of the neck. The greater the number of positive findings, the more likely intubation will be difficult. (See "Airway management for induction of general anesthesia", section on 'Difficult intubation'.)

IMPORTANCE OF AN ALGORITHMIC APPROACH — The American Society of Anesthesiologists (ASA) and other organizations have developed guidelines for management of the patient with a difficult airway that include algorithms to aid in clinical decision-making [1,4-6].(See 'Society guideline links' below.)

The guidelines from the ASA were updated in 2021, including new algorithms and infographics (algorithm 1 and figure 1) [1]. Important points in the new guidelines and graphics are as follows:

The new guidelines emphasize oxygenation prior to and throughout attempts at airway management.

Assessing the success of attempts at airway management should be primarily based on the detection of end tidal CO2 after each attempt at airway management, regardless of the airway device or technique used. The role of clinical measures (eg, chest rise and fall, misting, skin color) are considered secondary to CO2 detection.

Airway management attempts with each device or technique should be limited to three, with another attempt permitted by a more experienced airway operator.

The new guidelines provide more robust guidance for extubation than prior ASA guidelines.

A fundamental recommendation of these guidelines is for the performance of a thorough, pre-management assessment of the airway and other mitigating patient factors, with the goal of identifying patients at risk. Advanced recognition enables the practitioner to formulate a specific management plan that includes the possibility of securing the airway before induction of general anesthesia (ie, awake intubation). The algorithms that appear in guidelines proceed through specific decision points based on the success of the initial plan and the likelihood of success of backup techniques. Structured training and use of these algorithms for difficult airways may decrease airway-related morbidity [7,8]. Experienced personnel and specialized airway equipment are critical when airway management is difficult.

The importance of evaluation, planning, and an algorithmic approach to difficulty with airway management was demonstrated by an analysis of closed malpractice claims related to difficult intubation from 2000 to 2012 [9]. Airway management was judged to have been inappropriate in 73 percent of 102 assessed claims, and included inadequate evaluation, failure to plan for difficult intubation, failure to use a supraglottic airway for rescue, delay in calling for help, and perseveration on failed techniques.

AIRWAY APPROACH ALGORITHM — Our approach to developing an initial airway management strategy for the patient with a predicted difficult airway is summarized in the Airway Approach Algorithm (algorithm 2) [10]. This algorithm consists of a series of five clinical questions that lead the clinician to one of two entry points of the ASA Difficult Airway Algorithm (algorithm 1 and figure 1): awake intubation or intubation after induction of general anesthesia. The goal of this approach is to avoid entering the emergency pathway of the algorithm (ie, the "cannot intubate, cannot oxygenate," scenario). The questions used to direct airway management in the Airway Approach Algorithm include the following:

Is airway control required?

Could laryngoscopy be difficult?

Could supraglottic ventilation be used?

Is there risk of aspiration?

Will the patient tolerate a period of apnea?

The answers to these questions are combined to create a strategy for airway management.

PLANNING THE ANESTHETIC APPROACH — The plan for anesthesia and airway management for the patient with a predicted difficult airway may differ from the standard approach. The following discussion is applicable to the anesthetic care of these patients based on clinical assessment or prior history of difficulty. Creation of a general strategy for airway management is discussed more fully elsewhere. (See "Airway management for induction of general anesthesia", section on 'Creation of a strategy for airway management'.)

Regional versus general anesthesia — If appropriate for the surgical procedure, regional or local anesthesia may be preferable for the patient with a potentially difficult airway. Some patients, however, may require unanticipated airway manipulation or conversion to general anesthesia if the regional technique fails or is insufficient to complete the surgical procedure [1,4,11]. Thus, a plan must still be in place to manage the airway for patients having regional anesthesia [12]. In some cases, general anesthesia with elective management of the airway may be preferred to avoid an emergency difficult intubation should conversion become necessary (eg, due to inadequate regional block). This decision should be made on a case-by-case basis based on the likelihood of the regional anesthetic being successful and sufficient for the duration of the case, the degree of predicted airway difficulty, access to the airway during the case, the clinician's experience, and the availability of specialized airway equipment and skilled assistance [5].

Timing of airway control — Patients without a predicted difficult airway typically undergo anesthetic induction prior to intubation. In contrast, when a difficult airway is predicted, an awake intubation should be considered.

Awake intubation — Awake intubation should be considered if there is anticipated difficulty with tracheal intubation and any one of the following (algorithm 2 and algorithm 3 and figure 1):

Both mask and supraglottic airway (SGA) ventilation are likely to be difficult – Such patients are at risk for failed airway with standard induction techniques. Although the SGA has a high success rate following difficulty with both mask ventilation and direct laryngoscopy, there are patients for whom SGA use is likely to be difficult or to fail (table 3) [13]. (See "Airway management for induction of general anesthesia", section on 'Difficult supraglottic airway device use'.)

The stomach is not empty – Patients predicted to be difficult to intubate who have not fasted or who are otherwise at high risk for regurgitation and aspiration of gastric contents (table 5) should be intubated awake and in control of their airway reflexes whenever possible [1,5]. Airway topicalization can compromise airway protective reflexes and should be performed selectively, but thoroughly, in patients at high risk of aspiration. In such patients, the oropharynx can be anesthetized, and topical glossopharyngeal nerve blocks can be performed to blunt the gag reflex, but laryngeal and subglottic anesthesia should be avoided until immediately prior to intubation. This can be accomplished by spraying local anesthetic solution through the flexible intubation scope as it is advanced during the process of laryngoscopy and intubation. (See "Flexible scope intubation for anesthesia".)

The key to awake intubation in the patient with a full stomach is a smooth course, with avoidance of gagging, coughing, and vomiting. Whenever possible, the intubation should not be rushed. Rather, adequate time should be allowed for full local anesthetic effect. The rapid sequence induction and intubation (RSII) technique, which relies on the ability to intubate rapidly, may not be appropriate for the patient who may be difficult to intubate. (See "Rapid sequence induction and intubation (RSII) for anesthesia".)

The patient will not tolerate an apneic period – The risk of oxygen (O2) desaturation is greatest in patients with certain risk factors (eg, patients who are obese, are pregnant, or have pulmonary disease, as well as pediatric patients) (figure 2). When difficult laryngoscopy is anticipated, awake intubation should be considered even when mask or SGA ventilation is predicted to be easy.

The goal of awake intubation is to preserve spontaneous ventilation and patient cooperation while intubation is accomplished. Pediatric patients and those with cognitive disability, altered mental status, or extreme anxiety may not tolerate airway procedures while awake. When awake intubation is indicated but not feasible, induction of anesthesia with techniques that maintain spontaneous ventilation (eg, inhalation induction) may reduce the occurrence of failed airways [10]. A higher level of vigilance for the risk of aspiration or loss of the airway must be maintained. This may include preparations for an immediate surgical airway. (See "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

Airway management after induction — The Airway Approach Algorithm (algorithm 2) includes two scenarios in which it is appropriate to proceed with anesthetic induction prior to airway management:

Laryngoscopy is not predicted to be difficult – If laryngoscopy is not predicted to be difficult after a focused review of the patient's history and a physical evaluation of the airway, airway management can be attempted after induction of general anesthesia. Because of the relatively low sensitivities, specificities, and predictive values of the commonly performed airway exams, this determination is based in large part on clinical experience, including experience with the specific technique to be used (eg, direct or indirect laryngoscopy).

Laryngoscopy is predicted to be difficult, but ventilation by mask or SGA is predicted to be adequate, the patient is not at increased risk for aspiration, and the patient will tolerate an apneic period.

Choice of induction technique — Intravenous (IV) medication is used for induction of general anesthesia for most adult patients. If difficult airway management is predicted, IV induction is used when there is a high likelihood of successful ventilation by mask, SGA, or tracheal intubation and the patient is not at significant risk of gastric contents aspiration or rapid oxyhemoglobin desaturation. When maintenance of spontaneous ventilation throughout airway management is preferred, an inhalation induction may be used, though IV access should be established prior to inhalation induction. (See 'Inhalation induction' below.)

PLANNING THE AIRWAY MANAGEMENT APPROACH

Choice of airway device — Tracheal intubation is considered by many to be the definitive method of airway control for patients receiving general anesthesia. Not every patient, however, requires tracheal intubation, including the patient with a potentially difficult airway. Regardless of the technique chosen for airway management, a backup plan must be in place, with the necessary expertise and equipment immediately available. Techniques for use and various types of airway management devices are discussed separately. (See "Devices for difficult airway management in adults for emergency medicine and critical care".)

Facemask – Apart from the patient breathing spontaneously (with or without a general anesthetic), facemask ventilation is the most basic of airway management techniques. It can be used for short cases when the anesthesiologist will have full access to the patient's airway throughout the procedure, in patients without contraindications to application of a tight-fitting facemask (eg, facial fractures). An advantage to facemask airway management for the patient who may be difficult to intubate is that spontaneous ventilation can be maintained throughout the anesthetic. If mask ventilation is chosen, the surgeon must agree that the procedure could be interrupted for airway control during the case, if necessary. (See 'Mask or supraglottic airway ventilation' below.)

Supraglottic airway (SGA) – Many patients who are predicted to be difficult to intubate and/or mask ventilate can be successfully ventilated with an SGA. SGAs can be considered for use as the primary airway device when the risk of aspiration is relatively low and the need for higher airway pressures is not anticipated. An SGA specifically designed to allow intubation through the device may be a good choice for the patient who may be difficult to intubate. For longer procedures (ie, >3 hours) or for patients who will not be positioned supine, a second-generation SGA (with a gastric drain) should be strongly considered. (See 'Mask or supraglottic airway ventilation' below and "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults".)

Endotracheal tube (ETT) – Most anesthesiologists consider tracheal intubation to be the definitive form of airway control. The ETT affords the best protection of the airway against aspiration and allows controlled ventilation for long procedures performed in any position, with or without muscle relaxation and with high airway pressures if necessary. A comparison between SGA and ETT for airway management is discussed more fully elsewhere. (See "Airway management for induction of general anesthesia", section on 'Supraglottic airway versus endotracheal tube' and 'Tracheal intubation' below.)

Surgical airway — When the airway evaluation predicts that ventilation and tracheal intubation are likely to be impossible (eg, retropharyngeal abscess, large intraoral mass), a surgical airway may be indicated. In such cases, a surgeon should be consulted as part of the airway management plan. The surgeon should be asked whether emergent cricothyrotomy, tracheostomy, or rigid bronchoscopy would likely succeed if the airway is lost. If so, the surgeon and instrumentation for a surgical airway should be at the bedside during attempts at airway control. If not, tracheostomy under local anesthesia may be indicated. (See "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

Preprocedure extracorporeal membrane oxygenation (ECMO) — Patients who are at extremely high risk of complete tracheal obstruction with induction of anesthesia (eg, anterior mediastinal mass) and in whom a surgical airway is deemed impossible may benefit from establishing access for femorofemoral cardiopulmonary bypass/ECMO under local anesthesia before induction [14-18]. An example of such a case would be a large thyroid mass both compressing the trachea and preventing access to the trachea. (See "Anesthesia for patients with an anterior mediastinal mass".)

PREPARATION FOR DIFFICULT AIRWAY MANAGEMENT — Once the anesthetic and airway management plans are established, adequate preparation of necessary equipment, personnel, and the patient is essential.

Equipment preparation — Immediately prior to anesthesia, both routine and emergency airway equipment should be checked for availability and functionality. An assortment of standard and alternative airway devices should be immediately available, including facemasks, appropriate sizes and types of laryngoscopes (direct, indirect, flexible), oral and nasal airways, supraglottic airways (SGAs), bougies, and equipment for emergency invasive airway access. We keep emergency airway supplies and advanced airway equipment on a mobile cart, which should be in the anesthetizing location prior to induction of the patient with a potentially difficult airway, as recommended by the American Society of Anesthesiologists (table 6). (See "Airway management for induction of general anesthesia", section on 'Preparation for induction of anesthesia'.)

Patient preparation — Prior to the induction of anesthesia, care of the patient with a predicted difficult airway includes preoxygenation and careful positioning. Patients undergoing awake intubation need special consideration.

Preoxygenation and apneic oxygenation are discussed in detail separately. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

Preoxygenation – Preoxygenation should be performed prior to any airway intervention to delay oxyhemoglobin desaturation during periods of apnea or hypoventilation. Preoxygenation is especially important in patients who are prone to rapid desaturation during apnea, particularly if prolonged periods of apnea are expected due to difficulty with airway management. This includes pediatric patients and those who are obese or pregnant (figure 2). Patients with significant cardiopulmonary disease may not achieve maximal oxyhemoglobin levels and will thus have a shortened safe apneic period.

Preoxygenation is performed via a tight-fitting facemask using 100 percent oxygen (O2) at a flow rate high enough to prevent rebreathing (10 to 12 L/minute), aiming for an end-tidal concentration of O2 greater than 90 percent to maximize safe apnea time. Patients should be preoxygenated with either three minutes of tidal volume breathing or eight vital-capacity breaths over 60 seconds. These two techniques have been shown to be equally effective at preventing desaturation and are more effective than four vital-capacity breaths over 30 seconds [19-23].

Because the supine position reduces functional residual capacity (FRC), preoxygenation in the semi-upright or reverse Trendelenburg position is especially useful for patients with obesity or those with abdominal distention [24].

High flow nasal oxygen (HFNO) can be used for preoxygenation and apneic oxygenation if the equipment is available. HFNO for this indication is discussed separately. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

The use of positive airway pressure (noninvasive ventilation [NIV]) for preoxygenation has also been shown to prolong the time to desaturation during apnea [25]. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia", section on 'Positive airway pressure techniques during preoxygenation' and "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

Apneic oxygenation In addition to preoxygenation, we suggest the use of apneic oxygenation throughout laryngoscopy for patients at high risk of difficult intubation or rapid oxygen desaturation. Apneic oxygenation can be accomplished most simply with passive oxygen insufflation via nasal cannula at 10 to 15 L/minute. Alternatives include the THRIVE and SuperNO2VA nasal mask ventilation systems, where available. Apneic oxygenation techniques are unlikely to extend the safe apneic period in patients who have high grade obstructive lesions of the upper airway [26]. (See "Preoxygenation and apneic oxygenation for airway management for anesthesia", section on 'Apneic oxygenation' and "Preoxygenation and apneic oxygenation for airway management for anesthesia".)

Patient positioning – Proper positioning for induction of anesthesia and airway management of the patient with a difficult airway is essential. For direct laryngoscopy or video-assisted laryngoscopy (VAL) with a Macintosh-shaped blade, the head should be placed in the sniffing position (atlanto-occipital extension with the head elevated 3 to 7 cm), if possible. A neutral head position is preferred for highly-angulated videolaryngoscopes. Patients with obesity may require a ramped position, with head extension and the external auditory canal at the same level as the sternal notch, to improve intubating conditions (figure 3) [27].

Preparation for awake intubation – If awake intubation using a flexible intubation scope or other airway device is planned, preparation should include the administration of a drying agent (eg, glycopyrrolate 0.2 mg IV), nasal mucosal vasoconstrictors (if nasal intubation is a possibility), and anesthetic blocks (topical or invasive) of the upper airway. (See "Flexible scope intubation for anesthesia", section on 'Patient preparation'.)

SECURING THE AIRWAY

Airway timeout — An airway "time out," should be performed whenever there is an elevated risk of encountering a difficult airway. During an airway timeout, the following should be reviewed: airway plan, equipment and personnel availability, and back-up and rescue plans.

Induction of anesthesia — In patients with anticipated difficult to manage airways, the induction technique may be modified to ensure adequate ventilation or the ability to awaken the patient. Prior to induction, operating room personnel should be aware of the backup plan should difficulty arise. Further details regarding the induction of anesthesia are presented separately. (See "Induction of general anesthesia: Overview" and "Airway management for induction of general anesthesia", section on 'Intravenous induction'.)

Intravenous induction — Intravenous (IV) induction of general anesthesia is usually performed when there is a high likelihood of successful ventilation via facemask or supraglottic airway (SGA), or of successful intubation. For the patient with a difficult airway, an induction regimen that could allow return of spontaneous ventilation or awakening if attempts at ventilation are unsuccessful should be considered. General principles that should be followed include:

Induction agents — An adequate dose of short-acting medication should be used for induction (eg, propofol 1.5 to 2 mg/kg IV). Alternative intravenous induction agents, and the advantages, adverse effects, and dosing of anesthetic induction agents are discussed separately. (See "General anesthesia: Intravenous induction agents".)

Underdosing of induction agents may make mask ventilation or airway device placement more difficult.

Opioids — If an opioid is used as part of the induction regimen to reduce the physiologic response to intubation, a short-acting opioid is preferred (eg, fentanyl 1 to 2 mcg/kg IV), and naloxone should be immediately available for reversal should reestablishment of spontaneous ventilation be required. (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Opioids' and "General anesthesia: Intravenous induction agents", section on 'Opioids'.)

Neuromuscular blocking agents — Careful consideration should be given to the administration of neuromuscular blocking agents (NMBAs). NMBAs are administered for tracheal intubation because they improve intubating conditions by facilitating laryngoscopy and preventing reflexive laryngeal closure. We individualize the timing and selection of NMBA administration based on the preoperative airway assessment.

Timing of administration — The timing of administration of NMBAs relative to the establishment of mask ventilation is controversial. Classic teaching has been that mask ventilation should be established prior to the administration of NMBAs. In theory, 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 practice of withholding NMBAs until mask ventilation is established has been questioned because of studies reporting no change [28,29] or improvement in mask ventilation after administration of NMBAs in patients with normal airways [30] and predicted difficulty with mask ventilation [31]. NMBAs may improve mask ventilation, especially when difficulty is the result of laryngospasm, opioid-induced rigidity, or light anesthesia. In addition, withholding NMBAs could create a scenario in which mask ventilation and intubation are impossible (a "cannot ventilate, cannot intubate" situation) where there would otherwise not be one.

Our approach to the timing of NMBA administration for patients with predicted airway difficulty is as follows:

Difficult mask ventilation predicted – When mask ventilation is predicted to be difficult, but intubation is expected to be straightforward, we may choose a NMBA that provides a rapid onset of intubating conditions (eg, succinylcholine or high-dose rocuronium) without prior testing for the ability to ventilate by mask. (See 'Selection of NMBA' below.)

Difficult intubation predicted – When mask ventilation is predicted to be straightforward, and intubation is expected to be difficult, we do not test ventilation prior to the administration of NMBA.

Difficult mask ventilation and difficult intubation predicted – For patients in whom we predict difficulty with both mask ventilation and intubation, we perform awake intubation or inhalation induction of anesthesia, and we avoid the administration of NMBAs until the ability to ventilate is proven.

Selection of NMBA — For IV induction during predicted difficult airway management, the selection of NMBA should depend on which aspect of airway management is predicted to be difficult.

Difficult mask ventilation predicted – When mask ventilation is predicted to be difficult, but laryngoscopy is predicted to be straightforward, a strategy that allows rapid intubation while minimizing the need for mask ventilation should be employed. Options include:

Succinylcholine – Succinylcholine is a depolarizing NMBA. At a dose of 1 to 1.5 mg/kg IV, neuromuscular block is complete in approximately one minute, and recovery occurs in six to nine minutes [32].

Rocuronium – Rocuronium is a nondepolarizing NMBA. At a dose of 0.9 to 1.2 mg/kg IV, neuromuscular block is complete in less than two minutes, with a variable, long duration of action (38 to 150 minutes) [33].

Remifentanil – Remifentanil is an ultrashort-acting opioid that can be administered (3 to 5 mcg/kg IV with ephedrine 10 mg IV) in place of NMBAs to achieve adequate intubating conditions without paralysis [34-36]. (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Remifentanil intubation' and "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Neuromuscular blocking agents (NMBAs)'.)

Difficult intubation predicted – When mask ventilation is predicted to be straightforward but intubation is likely to be difficult, a strategy that provides optimal intubating conditions should be employed. It is important to remember, however, that the ability to mask ventilate may deteriorate with prolonged attempts at airway management.

Options include:

Succinylcholine, which provides a rapid onset of muscle relaxation, though its duration of action is variable (six to nine minutes) [32].

Rocuronium and vecuronium, which are intermediate-acting nondepolarizing NMBAs.

Depending on the dose administered, rocuronium and vecuronium can provide optimal intubating conditions in one to three minutes. A certain degree of spontaneous recovery must occur before these agents can be reversed with neostigmine, which can take 20 minutes to over an hour depending on the specific agent and the dose administered. Reversal of deep blockade (after administration of rocuronium 1.2 mg/kg) can be achieved with 16 mg/kg of sugammadex, a chelating reversal agent. Rapid reversal of deep rocuronium block with sugammadex is significantly faster than spontaneous recovery of succinylcholine block, but it can still require more than six minutes [37]. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Sugammadex'.)

We do not employ a high-dose remifentanil technique when difficult intubation is predicted because the resultant opioid-induced glottic closure and the lack of muscle relaxation may not provide optimal intubating conditions and may render mask ventilation difficult. (See "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Remifentanil intubation' and "Rapid sequence induction and intubation (RSII) for anesthesia", section on 'Neuromuscular blocking agents (NMBAs)'.)

Inhalation induction — Though IV induction is most often used in adults, inhalation induction can be used when the clinician wants to maintain spontaneous ventilation until airway control (with facemask, SGA, or tracheal intubation) has been confirmed. This may be preferred in patients predicted to have difficulty with intubation but not with mask ventilation. IV access should be obtained in adults prior to inhalation induction when difficulty with airway management is anticipated.

Following preoxygenation with a tight-fitting face mask, a volatile anesthetic is administered, starting at a low, gradually increasing concentration. Sevoflurane is the agent of choice as its lack of pungency makes it generally well tolerated by the awake patient, and its pharmacokinetics are such that it redistributes rapidly if airway obstruction occurs. Slowly increasing concentrations of sevoflurane leads to progressive central nervous system depression, typically with the preservation of spontaneous respirations. If airway obstruction occurs at any point during the induction, sevoflurane is discontinued, and redistribution results in awakening, typically with resolution of the obstruction.

We avoid the addition of nitrous oxide (N2O) for induction when a difficult airway is expected. While N2O speeds induction, it must be administered at a high concentration to be effective, thereby limiting the fraction of inspired oxygen (FiO2) and decreasing the safe apneic period.

The patient may be intubated without muscle relaxation from deep inhalation anesthesia, such as 6% exhaled sevoflurane. Although patients usually require ventilatory assistance to maintain adequate minute ventilation at this deep level of anesthesia, a benefit of continuing spontaneous ventilatory efforts is that it speeds emergence if it is necessary to awaken the patient. Hypotension is likely at this level of anesthesia, and vasopressor support may be necessary.

Alternatively, the clinician may support spontaneous respiratory efforts with increasing positive-pressure assistance by mask until ventilation is completely controlled. Once mask ventilation is established, IV induction agents, opioids, or NMBAs may be administered to optimize conditions for laryngoscopy and intubation.

Mask or supraglottic airway ventilation — After induction of anesthesia in the patient with a difficult airway, mask ventilation should be established with 100 percent oxygen. Successful facemask ventilation depends on both patient factors and the skill of the clinician. In most patients, at least some air movement is possible, although two-person ventilation and airway adjuncts may be needed; only a small number of patients are actually impossible to ventilate and thus are at risk of a failed airway. For example, in an observational study, impossible mask ventilation was present in only 0.15 percent of patients [38].

Various maneuvers may improve the ability to mask ventilate (see "Basic airway management in adults"):

Placement of an oropharyngeal (or nasopharyngeal) airway

Maneuvers to open the upper airway (eg, head tilt, chin lift (picture 1), or jaw thrust (picture 2))

Two-person mask technique (two-handed mask technique (picture 3) with a second person to ventilate)

Patients with inadequate ventilation despite these maneuvers should have an SGA placed. This is the primary rescue technique for patients with difficult or impossible mask ventilation, and most patients with difficult mask ventilation may be successfully ventilated using a SGA [13]. Success with SGA ventilation is dependent on the clinician's skill and experience with specific devices. A variety of types and sizes of SGAs are available; difficult ventilation can often be overcome by using an alternative.

Whenever both mask and SGA ventilation are impossible, skilled assistance should be summoned and tracheal intubation attempted. If unsuccessful, the emergency pathway in the American Society of Anesthesiologists (ASA) Difficult Airway Algorithm should be followed and the patient awakened, if possible. Emergency invasive airway access may be necessary (algorithm 1 and figure 1). (See "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

Tracheal intubation — The choice of airway technique or device for intubation 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. For patients with expected difficulty with laryngoscopy and intubation, we suggest the use of an advanced airway technique (eg, video laryngoscopy, flexible scope intubation) for the first attempt at intubation, rather than DL. The comparison of outcomes with VL versus DL is discussed separately. (See "Video laryngoscopes and optical stylets for airway management for anesthesia in adults", section on 'VL versus DL' and "Flexible scope intubation for anesthesia".)

Direct laryngoscopy (DL) is the most common and usually the quickest technique for tracheal intubation. Alternatives to direct laryngoscopy include indirect laryngoscopy (eg, with a videolaryngoscope [VL] or optical stylet), intubation through an intubating SGA, and flexible scope intubation (FSI). FSI while asleep is more difficult than while awake due to relaxation of the pharyngeal tissues. FSI through an endoscopy mask or an SGA permits ventilation during intubation.

Flexible intubation scopes are the most commonly used devices for awake intubation, but other advanced airway devices may also be used in this setting, depending on the experience of the clinician and patient factors. The rate of successful intubation with a variety of VL devices is equivalent to that with flexible scopes, and may be faster. Alternatives may be chosen when flexible scope intubation would be difficult. For example, when blood or secretions soil the airway, a bladed technique such as video-assisted or direct laryngoscopy may allow better visualization of the larynx. Awake placement of a laryngeal mask airway (LMA), a type of SGA, has been described, either to facilitate tracheal intubation or for ventilation for the anesthetic. These techniques are discussed separately. Airway management techniques are discussed separately. (See "Flexible scope intubation for anesthesia" and "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults" and "Direct laryngoscopy and endotracheal intubation in adults".)

Unanticipated difficult intubation — Following an unsuccessful initial intubation attempt, resumption of ventilation is the priority, either by noninvasive (ie, face mask, SGA) or invasive means, or by awakening the patient. Repeated attempts at intubation should not delay noninvasive airway ventilation or emergency invasive airway access. We prefer to use an intubating SGA as the initial rescue device after two failed attempts at direct laryngoscopy if mask ventilation is not adequate. An intubating SGA permits immediate ventilation and may facilitate intubation with a standard-size endotracheal tube, without the need for an airway exchange catheter. (See "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults", section on 'Supraglottic airways as conduits for intubation'.)

Repeated instrumentation of the airway may lead to bleeding, edema, and deterioration of the ability to ventilate. For this reason, laryngoscopy attempts with any particular device should be limited. Data suggest that complications increase when more than two attempts at direct laryngoscopy are made [39]. Intubating conditions should be optimized between attempts; for example, by improving head and neck position, changing laryngoscope blade, using a different device, or by having a more experienced clinician manage the airway.

Following initially unsuccessful attempts at intubation, no single subsequent technique is superior to others in all circumstances. For example, in one series of 698 patients with both difficult mask ventilation and difficult laryngoscopy, intubation was eventually successful with direct laryngoscopy in 177, direct laryngoscopy with bougie introducer in 284, VL in 163, and other techniques in 73; one patient required emergent cricothyrotomy [40]. These devices and their use are discussed elsewhere. (See "Flexible scope intubation for anesthesia" and "Direct laryngoscopy and endotracheal intubation in adults" and "Supraglottic devices (including laryngeal mask airways) for airway management for anesthesia in adults" and "Video laryngoscopes and optical stylets for airway management for anesthesia in adults".)

Based on the review of large data sets, expert groups have suggested that VL should be the first rescue technique employed when direct laryngoscopy and/or mask or SGA ventilation have failed, because of high success rates. In a large, multicenter retrospective study of failed DL utilizing the Multicenter Perioperative Outcomes Database, in 1619 rescue attempts, VL resulted in the highest success rate (92 percent), compared with FSI (78 percent), use of an SGA as a conduit for intubation (78 percent), or the use of a lighted stylet (77 percent) [41].

THE FAILED AIRWAY — The inability to either ventilate or intubate a patient is termed a "failed airway." With adequate planning and an algorithmic approach to airway management, the failed airway should be an extremely rare event.

Help should be summoned as soon as difficulty is encountered, and the emergency pathway of the difficult airway algorithm should be followed (algorithm 1). After failure of multiple attempts at intubation and facemask or SGA ventilation, emergency invasive airway access should be performed. A reasonable approach is to use no more than three attempts at intubation or SGA ventilation before performing an emergency invasive airway. An additional attempt by a clinician with higher skill may be warranted [1]. Emergency invasive airway management techniques include cricothyrotomy, surgical tracheotomy, and transtracheal jet ventilation. Choice of technique depends on the expertise of the clinician, availability of equipment and personnel, and technical patient factors. (See "Management of the failed airway during anesthesia".)

EXTUBATION — Adverse airway events are common at the time of extubation [42-46]. While most of the problems that occur during extubation are minor, rarely they may result in hypoxic injury or death. 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.

Prior to extubation of the difficult or at-risk airway, an extubation strategy must be formulated that includes a plan for reintubation if necessary, including the same assortment of personnel and equipment that were present at induction. Risk stratification and strategies for management of routine and at-risk extubation are discussed in detail separately. (See "Extubation following anesthesia".)

DIFFICULT AIRWAY MANAGEMENT IN THE TRAUMA PATIENT — Patients with traumatic injury should be presumed to have difficult airways. They should be treated with full stomach precautions, and depending on the specific injury, may be at risk for cervical spine injury. (See "Initial management of trauma in adults", section on 'Cervical spine immobilization'.)

Airway management for trauma patients may be complicated by time pressure, hemodynamic instability, and lack of patient cooperation with examination and procedures.

Some of the management strategies that are usually followed for patients without traumatic injury may be inappropriate in patients with trauma. As examples, awakening the trauma patient if difficulty occurs is rarely an option, and awake intubation may be impractical or contraindicated, even when an impossible to manage airway is recognized. Thus, emergency invasive airway access may the best first choice management option in some patients with trauma. An approach to difficult airway management in trauma patients is shown in an algorithm (algorithm 4). Airway management for trauma patients is discussed separately, and is shown in tables (table 7 and table 8 and table 9 and table 10). (See "Anesthesia for adults with acute spinal cord injury", section on 'Airway management' and "Anesthesia for patients with acute traumatic brain injury", section on 'Airway management' and "Anesthesia for adult trauma patients", section on 'Airway management'.)

AIRWAY MANAGEMENT FOR PATIENTS WITH COVID-19 — Patients with novel coronavirus disease 2019 (COVID-19 or nCoV) often require airway management for respiratory failure or other reasons (eg, non-elective surgery). For patients who are predicted to have difficulty with airway management, the risk of transmission of the virus to health care providers must be considered, while emphasizing patient wellbeing and successful airway management. Special considerations for airway management in the COVID-19 positive patient are discussed separately. (See "Overview of infection control during anesthetic care", section on 'Infectious agents transmitted by aerosol (eg, COVID-19)'.)

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

Algorithmic approach – We use algorithms to systematically plan induction and airway management for the patient with a potentially difficult airway (algorithm 1 and figure 1 and algorithm 2). The approach begins with assessment of the airway and other patient factors, and proceeds through specific decision points based on success of the initial plan and likelihood of success of backup techniques. (See 'Planning the anesthetic approach' above.)

Identify the difficult airway – The best indication that a patient may be easily ventilated or intubated is a history of prior success. In the absence of prior records, the best available methods to predict difficulty with mask ventilation (table 2), supraglottic airway (SGA) ventilation (table 3), and direct laryngoscopy (table 4) are based on physical examination of the airway and a review of comorbid conditions. (See 'Recognition of the difficult airway' above.)

Consider awake intubation

Awake intubation should be considered if there is anticipated difficulty with tracheal intubation AND one of the following (algorithm 2 and algorithm 1) (see 'Awake intubation' above):

-Both mask and supraglottic airway (eg, laryngeal mask airway [LMA]) ventilation are likely to be difficult

-The stomach is not empty (the patient is at risk for aspiration of gastric contents)

-The patient will not tolerate an apneic period (eg, severe obesity, pregnancy, pulmonary disease)

When at least one method of airway management has a high likelihood of success, most patients may be induced in the standard fashion (with intravenous [IV] agents prior to intubation) with some modification in technique. Inhalation induction may be indicated in certain patient populations to preserve spontaneous ventilation until the airway is controlled. (See 'Induction of anesthesia' above.)

Airway management after induction of anesthesia – We manage the difficult airway according to the American Society of Anesthesiologists (ASA) Difficult Airway Algorithm (algorithm 1 and figure 1).

Check emergency airway equipment (table 6) and discuss backup airway plans with assisting personnel, whether the initial plan is for mask ventilation, use of a SGA, or tracheal intubation. In rare cases, the safest plan may be a tracheostomy under local anesthesia, or a surgeon standing by during airway management for a possible emergency surgical airway.

Position the patient for laryngoscopy and preoxygenate with 100 percent oxygen (O2) using a tight-fitting facemask for three to five minutes, eight deep breaths over one minute, or until expired concentration of O2 reaches 90 percent. (See 'Equipment preparation' above and 'Patient preparation' above.)

Place an SGA promptly in patients with inadequate mask ventilation despite best efforts. Maintenance of adequate ventilation is the first priority. Whenever both mask and SGA ventilation are impossible, skilled assistance should be summoned and intubation attempted. Awakening the patient or using emergency invasive airway access should be considered if the patient is not quickly intubated. (See 'Mask or supraglottic airway ventilation' above.)

Intubate using a familiar technique judged to have the greatest likelihood of success in the specific patient. For patients with expected difficulty with laryngoscopy and intubation, we use an advanced airway technique (eg, video laryngoscopy, flexible scope intubation) for the first attempt at intubation, rather than direct laryngoscopy. (See 'Tracheal intubation' above and "Video laryngoscopes and optical stylets for airway management for anesthesia in adults", section on 'VL versus DL'.)

If repeated attempts at intubation are required, conditions should be optimized between attempts, including repositioning and changing to more experienced personnel. We limit repeat attempts at intubation as they may result in edema, trauma, bleeding, and deterioration of ventilation. (See 'Unanticipated difficult intubation' above.)

Emergency invasive airway access, including surgical or percutaneous airway and transtracheal jet ventilation, may be required when ventilation is inadequate and intubation attempts have failed. (See 'The failed airway' above.)

Extubation – Airway complications are common at the time of extubation. A plan should be in place for extubation and the immediate postoperative period for the patient with a difficult airway. (See 'Extubation' above and "Extubation following anesthesia".)

Patients with trauma – Patients with traumatic injury should be presumed to have a difficult airway. They should be treated with full stomach precautions, and may be at risk for cervical spine injury. Options for airway management in trauma patients may be limited by lack of patient cooperation and time constraints. Awakening the patient after failed airway management is rarely an option (algorithm 4). (See 'Difficult airway management in the trauma patient' above.)

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Topic 90615 Version 35.0

References

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