Approach to the failed airway in adults for emergency medicine and critical care

INTRODUCTION — A failed airway exists when there is a failure to perform gas exchange in a patient that cannot do so on their own. In this setting, clinicians must act quickly, using a deliberate approach to ensure that oxygenation is preserved. Although placement of a definitive airway is desired for a failed airway, the chief objective is to maintain adequate oxygenation and prevent hypoxic injury. This may or may not be accomplished by placement of a cuffed endotracheal tube.

The approach and management of the failed airway in adults outside of the operating room is reviewed below. Other aspects of airway management, including the use of rescue devices and the performance of airway procedures, are discussed separately, including the following topics:

●Adult emergency airway management: (see "Rapid sequence intubation in adults for emergency medicine and critical care" and "Approach to the difficult airway in adults for emergency medicine and critical care")

●Pediatric emergency airway management: (see "Rapid sequence intubation (RSI) in children for emergency medicine: Medications for sedation and paralysis" and "Technique of emergency endotracheal intubation in children" and "The difficult pediatric airway for emergency medicine")

●Emergency airway procedures: (see "Emergency cricothyrotomy (cricothyroidotomy) in adults" and "Direct laryngoscopy and endotracheal intubation in adults" and "Endotracheal tube introducers (gum elastic bougie) for emergency intubation" and "Extraglottic devices for emergency airway management in adults" and "Basic airway management in adults")

DEFINITIONS — A failed airway exists when there is a failure on the part of the operator to perform gas exchange in a patient that cannot do so on their own. In the clinical arena, this most often occurs when there is an inability to intubate the patient's trachea (even after only a single failed attempt) and an inability to maintain oxyhemoglobin saturations with either a bag and mask or extraglottic device. This is the "can't intubate, can't oxygenate" type of failed airway. The term "failed airway" therefore is applied at any point at which the primary airway management technique is unsuccessful, and alternative techniques are not able to maintain oxygenation. When this situation arises during emergency airway management, the clinician must take immediate action to avoid critical oxygen desaturation (<80 percent) with resultant cerebral hypoxia.

For emergency airway management, a second form of failed airway has been defined as three failed attempts to place a definitive airway by an experienced operator, even when bag and mask ventilation is capable of maintaining adequate oxyhemoglobin saturation [1]. This is the "can't intubate, can oxygenate" type of failed airway. In this scenario, the clinician must plan to use alternative strategies to place a tracheal tube or ensure continued gas exchange; the latter is often accomplished through the placement of an extraglottic device.

A failed airway (failure of intubation, failure of oxygenation, or both) can arise during a rapid sequence intubation, during management of a difficult airway, or during management of a crash airway. Regardless of the circumstances leading to the airway failure, a deliberate approach must be used to ensure that oxygenation is preserved, and that the airway is ultimately secured.

INCIDENCE OF THE FAILED AIRWAY — The true incidence of the failed airway, as defined above, is not known for emergency department (ED) airway management, nor for patients undergoing anesthesia in the operating room. An analysis of ED intubations [2] in the National Emergency Airway Registry found that ultimate intubation success with rapid sequence intubation is 99.6 percent when succinylcholine is used and 99.9 percent with rocuronium. Rescue surgical cricothyrotomy (also called cricothyroidotomy), a surrogate marker for the "can't intubate, can't oxygenate" emergency failed airway, is required in approximately 0.3 percent of all emergency intubations [3,4]. (See "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

It is likely that the incidence of failed airway, particularly of the can't intubate, can ventilate type, is higher than this in general community practice, as the NEAR sites were mostly academic medical centers. Regardless, the failed airway represents a potential catastrophe if not managed effectively. The failed airway scenario is best avoided whenever possible by a systematic pre-intubation evaluation of patients for anatomic and physiologic difficult airway attributes and thorough planning for the intubation, including planning for failure. (See "Approach to the difficult airway in adults for emergency medicine and critical care".)

REDUCING THE RISK OF A FAILED AIRWAY — The risk of a failed airway during emergency intubation cannot be eliminated, but several measures should be taken to mitigate such risk. These measures include the following:

●Perform pre-intubation assessment of risk whenever possible (see "Approach to the difficult airway in adults for emergency medicine and critical care", section on 'Identifying the anatomically difficult airway')

●Maximize preoxygenation (see "Rapid sequence intubation in adults for emergency medicine and critical care", section on 'Preoxygenation')

●Employ capnography to monitor patients (see "Carbon dioxide monitoring (capnography)")

●Use video laryngoscopy (see "Video laryngoscopes and optical stylets for airway management for anesthesia in adults")

●Before rapid sequence intubation medications are administered, determine a secondary and tertiary (rescue) strategy should intubation or oxygenation fail

The significance of the pre-intubation evaluation was underlined by a study performed in the United Kingdom in 2010. The National Audit Project 4 (NAP4) identified a higher likelihood of adverse outcome (permanent brain injury or death) for emergency department (ED) and intensive care unit (ICU) intubations when compared with those occurring in the operating room (OR). The investigators attributed this to various factors, most notably failure to perform adequate pre-intubation assessment to identify at-risk patients, and failure to use capnography [5]. The emergent nature of the intubations in the ED and ICU likely contributed as well. Other studies have identified increased risk of adverse events with an increasing number of attempts required to achieve intubation [6,7]. The National Emergency Airway Research (NEAR) III investigators found an increasing use of video laryngoscopy in the later years of their 10-year study period and a decreasing incidence of airway failure and cricothyrotomy, suggesting that optimizing laryngeal view by using video laryngoscopy may increase success and decrease the likelihood of a failed airway [3]. This was reinforced in a subsequent NEAR analysis showing that use of either hyper-angulated or standard geometry video laryngoscopes improved the chance of a first-attempt success two- to threefold over direct laryngoscopy (DL), even when DL was aided by laryngeal manipulation, ramping, or use of a tracheal tube introducer ("bougie") [8-10].

Robust preoxygenation is crucial for prolonging the apnea time during rapid sequence intubation. Flush-flow rate oxygen and apneic oxygenation are effective methods for maximizing preoxygenation and prolonging safe apnea, both of which can help decrease the risk of a failure of oxygenation during emergency airway management. (See "Rapid sequence intubation in adults for emergency medicine and critical care", section on 'Preoxygenation'.)

THE FAILED AIRWAY ALGORITHM AND APPROACH

Overview of algorithm — When a failed airway occurs, the failed airway algorithm provides a series of actions to guide management (algorithm 1) [1,11]. The critical question is whether adequate oxygenation (ie, oxyhemoglobin saturation [SpO₂] above 90 percent or stable in the high 80s) can be maintained. If oxygenation is adequate and stabilized, there is time to plan a series of actions to manage the airway; if the patient's oxygenation cannot be maintained, rescue by (usually) cricothyrotomy is necessary. (See "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

If time permits, there are a number of alternative or rescue devices that can be used when direct laryngoscopy has failed. In some cases, the rescue airway may provide a definitive airway, with a cuffed endotracheal tube (ETT) in the trachea. If the airway is secured by a cuffed ETT, the airway is considered to be managed, and general resuscitation continues. If adequate oxygenation and ventilation are achieved, but the airway is not protected by a cuffed ETT in the trachea, resuscitation can continue, but arrangements must be made to establish a definitive airway at the earliest appropriate opportunity. (See "Extraglottic devices for emergency airway management in adults".)

As with the difficult airway algorithm, the response to the failed airway can be thought of as a series of discrete steps. Each of these steps is described in detail below. Assistance in the form of personnel, equipment, or airway devices, should be obtained as needed at the moment the failed airway is recognized.

Is there time? — At the outset, the key determination is whether the patient is being adequately oxygenated (ie, oxyhemoglobin saturation [SpO₂] above 90 percent or stable in the high 80s). If so, there is time to create and execute a deliberate rescue plan, perhaps customized to the patient's particular circumstances. This is the "can't intubate, can oxygenate" scenario.

If the patient cannot be oxygenated adequately with a bag and mask, despite optimal bagging technique and adjunct airway devices (ie, can't intubate, can't oxygenate), immediate cricothyrotomy is indicated. Although an alternative airway device might rescue the patient without cricothyrotomy, the extremely brief time before cerebral hypoxia ensues argues for immediate surgical intervention. Multiple attempts to establish an alternative airway, if unsuccessful, may delay the initiation of cricothyrotomy leading to hypoxic brain injury. Thus, we equate "can't intubate, can't oxygenate" with cricothyrotomy in the emergency setting. (See "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

There is one important, optional modification to this approach. Placement of a single "best" alternative device, usually an extraglottic airway (eg, iGel supraglottic airway or King laryngeal tube [LT] airway) can be attempted in parallel with preparations for the surgical airway. If the operator is able to insert an extraglottic airway and attempt ventilation, while a second clinician simultaneously prepares for a cricothyrotomy, then valuable time is not lost if oxygenation is unable to be restored using the extraglottic device. (See "Extraglottic devices for emergency airway management in adults".)

Similarly, a single operator might make one attempt with an extraglottic device, then proceed directly to cricothyrotomy if oxygenation is not promptly achieved. This approach involves a single attempt using a single "go to" device, and cannot delay significantly the initiation of cricothyrotomy if ventilation is not achieved immediately. Optimally, an i-gel would be used for this single attempt, as placement is rapid and attempts at ventilation can occur immediately without the need for cuff or balloon inflation. (See "Extraglottic devices for emergency airway management in adults", section on 'i-gel'.)

Whether this single, parallel rescue maneuver is attempted but unsuccessful or not attempted, the primary rescue technique is cricothyrotomy. The performance of cricothyrotomy is discussed separately. (See "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

Is there a role for sugammadex ? — Sugammadex is a reversal agent for nondepolarizing neuromuscular blockers. The appropriate role for sugammadex in salvaging a "can't intubate, can't oxygenate" failed airway in the emergency department (ED) when rocuronium is used remains unclear. Little evidence from outside the operating room is available to inform the use of sugammadex for failed airway management. Pending further research, we recommend that emergency providers avoid reliance on sugammadex and follow the algorithmic approach outlined here by rapidly enacting plans for rescue oxygenation using an extraglottic device and surgical rescue. (See "Clinical use of neuromuscular blocking agents in anesthesia", section on 'Sugammadex'.)

There are several reasons for avoiding sugammadex in the ED. When a patient's oxygen saturation is dropping, the time required to administer and allow sugammadex to work could be costly, allowing further clinical deterioration. As part of rapid sequence intubation, patients are given a high dose of a sedative induction agent, causing them to remain obtunded and hypopneic even after sugammadex is given and muscle twitch is restored. Treatment with sugammadex does not reverse or treat the original condition that prompted emergency intubation, and the clinician will still be left with a patient who requires airway rescue. Delay in providing a surgical airway in a "can't intubate, can't oxygenate" scenario is an area of medical-legal risk for emergency physicians in some countries. Sugammadex may entice providers to delay cricothyrotomy in the hopes that reversal will rapidly restore pre-intubation pulmonary mechanics. This will likely not be the case.

ALTERNATIVE AIRWAY DEVICES — In contrast to difficult airway management, during which placement of a cuffed endotracheal tube (ETT) in the trachea is the goal, the initial objective for failed airway management is to provide adequate oxygenation sufficient to support the patient until a definitive airway can be achieved. So long as the patient is adequately oxygenated using a bag and mask, the clinician may use any of several alternatives to direct laryngoscopy to rescue the failed airway. The devices briefly described below are discussed in detail separately. (See "Devices for difficult airway management in adults for emergency medicine and critical care".)

List of devices

●Video laryngoscopes – We prefer that a video laryngoscope be used as the primary intubating device for most intubations [12]. However, if a direct laryngoscope is used instead, a video laryngoscope should be used as a first rescue device if available.

Video laryngoscopes (eg, Storz C-MAC, Glidescope, KingVision) resemble a conventional laryngoscope with a video camera on the blade that generally provides an improved glottic view without the need to align the airway axes to achieve a direct view from outside the patient's mouth. These devices function well with the patient in a neutral position (ie, without neck flexion or extension), and obstacles to conventional laryngoscopy, such as limited mouth opening or a large tongue, generally do not present a problem. (See "Video laryngoscopes and optical stylets for airway management for anesthesia in adults", section on 'Videolaryngoscopy' and "Devices for difficult airway management in adults for emergency medicine and critical care", section on 'Video laryngoscopes'.)

●Optical devices – Various optical devices may be used for intubation of the failed airway or as an alternative to direct or video laryngoscopy. The best studied of these is the AirTraq, a periscope-like device that uses prisms and mirrors to provide an indirect view of the glottis comparable to that provided by a video laryngoscope but with inferior image quality. The AirTraq incorporates a channel for the ETT, which is advanced when the glottis is properly sighted. Many optical devices can be fitted with camera adjuncts or caps that transmits the image in the eyepiece to a small digital screen. (See "Video laryngoscopes and optical stylets for airway management for anesthesia in adults", section on 'Channeled VL' and "Devices for difficult airway management in adults for emergency medicine and critical care", section on 'Optical laryngoscopes'.)

●Extraglottic airways – Various supraglottic airways are available, some specifically designed to facilitate blind intubation and some intended strictly as ventilatory devices. These devices include a oval-shaped, often inflatable, mask that fits above the glottic inlet to create a trapped gas space for oxygenation and ventilation. Examples include the laryngeal mask airway (LMA), Aura-I, iGel, and AirQ supraglottic airways. A second type of extraglottic airway is inserted into the esophageal inlet and has two balloons that are inflated to occlude both the esophagus and the pharynx, thereby permitting side-stream ventilation of the trachea. These are coined infraglottic airway because the distal tip is meant to be placed beyond the glottic opening and into the cervical esophagus. An example is the King laryngeal tube (LT). (See "Extraglottic devices for emergency airway management in adults".)

●Flexible bronchoscope – The flexible bronchoscope, preferably a video intubating bronchoscope, provides access to the glottis without having to correct for the various angles of the oropharynx, as is required for direct laryngoscopy. Intubation can be achieved nasally or orally. The latter approach can be used with the scope alone and advanced through the oral cavity or via an extraglottic device that is already in place. By either route, attempts can be time-consuming, making this device more appropriate for a planned approach to certain difficult airways, rather than for the rescue of a failed airway. Attempts using the flexible bronchoscope may have to be abbreviated or abandoned because of the difficulty maintaining oxygenation during flexible endoscopic airway procedures. Flexible bronchoscopes require training and practice, but have high success rates when time permits [13]. (See "Flexible bronchoscopy in adults: Overview" and "Flexible bronchoscopy in adults: Preparation, procedural technique, and complications" and "Flexible bronchoscopy in adults: Indications and contraindications".)

Was a cuffed endotracheal tube placed in the trachea? — Many of the alternative airway devices listed above result in a cuffed ETT in the trachea, in which case, the airway is secured. Others, such as the extraglottic airways, provide for ventilation and oxygenation, but do not protect the airway. If one of the nonprotective devices has been used, resuscitation can proceed, but a plan must be initiated to secure the airway at the earliest opportunity. If at any time oxygenation fails, and the patient reverts to a "can't intubate, can't oxygenate" situation, cricothyrotomy remains the rescue technique of first resort.

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".)

SUMMARY AND RECOMMENDATIONS

●Definitions – A failed airway exists at any time during an attempt at endotracheal intubation when there is an inability to intubate the patient (even with a single attempt) and an inability to oxygenate the patient adequately using a bag and mask or an extraglottic device (ie, maintain oxyhemoglobin saturations [SpO₂] above 90 percent or stable in the high 80s). This is the "can't intubate, can't oxygenate" type of failed airway. A failed airway also exists when there have been three failed attempts to intubate by an experienced operator, even when ventilation with a bag and mask or an extraglottic device maintains adequate SpO₂. This is the "can't intubate, can oxygenate" type of failed airway. (See 'Definitions' above.)

●Cricothyrotomy: Primary rescue maneuver – We recommend that cricothyrotomy be used as the primary rescue maneuver for the "can't intubate, can't oxygenate" failed airway. Cricothyrotomy has a high success rate and relatively low complication rate. The methods for performing cricothyrotomy are described in detail separately. (See 'The failed airway algorithm and approach' above and "Emergency cricothyrotomy (cricothyroidotomy) in adults", section on 'Preferred technique: Scalpel-finger-bougie'.)

Prior to undertaking cricothyrotomy, it is reasonable for the operator make a single attempt to quickly place an extraglottic airway, provided the attempt does not delay initiation of cricothyrotomy for more than 30 seconds.

●Critical question: Is oxygenation adequate? – The critical question in failed airway management is whether adequate oxygenation (ie, SpO₂ above 90 percent or stable in the high 80s) can be maintained. If oxygenation is adequate, there is time to plan subsequent airway management; if oxygenation cannot be maintained, immediate rescue by (usually) cricothyrotomy is necessary. (See 'The failed airway algorithm and approach' above and "Emergency cricothyrotomy (cricothyroidotomy) in adults".)

Pending further evidence, the reversal agent sugammadex should not be relied upon to rescue a "can't intubate, can't oxygenate" failed airway in emergency department (ED) patients. (See 'Is there a role for sugammadex ?' above.)

●Rescue devices – For the "can't intubate, can oxygenate" patient, there are several possible rescue devices. (See 'Alternative airway devices' above.)

For ventilation only: Extraglottic airway (eg, Combitube, King LT, Laryngeal mask airway)

For intubation:

•Intubating LMA

•Rigid fiberoptic or video stylet

•Video laryngoscope

•Optical device (eg, AirTraq)

•Flexible endoscope

ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge Michael Murphy, MD, FRCPC who contributed to an earlier version of this topic review.