What Is the Challenge of Difficult and Failed Airway Management?

Competency with regard to airway management is fundamental to the practice of anesthesia, emergency medicine, emergency medical services (EMS), critical care medicine, hospital medicine, and other acute care specialties. The focus of this chapter is the management of the difficult and failed airway in an emergency or urgent situation. Management of the predicted difficult intubation is dealt with in Chapter 3 and in Section 2 of this book.

The airway practitioner in an urgent or emergency situation is faced with two particular challenges: to be able to accurately and expeditiously predict a difficult airway, and to be able to recognize when airway management has failed.¹ No matter the situation, reliably and reproducibly ensuring timely and effective oxygenation and ventilation is imperative.

Appropriate planning, selection of the airway devices and techniques, clear communication of that plan and calm execution based on learned methods and experience enhances success even in these most difficult cases. The need for clearly communicated Plan A (first line or initial plan), B (backup or salvage plan), and C (failed airway plan) cannot be over emphasized.

How Reliably Can We Predict a Difficult Airway?

There are five means through which effective ventilation occurs:

• 
  

  Spontaneous patient driven

  
  

  And ventilation provided through:

  
  
• 
  

  Bag-mask (BMV)

  
  
• 
  

  Extraglottic device (EGD)

  
  
• 
  

  Endotracheal intubation

  
  
• 
  

  Surgical airway

The latter four of these are artificial or nonnatural interventions, or methods of active airway management. In the event that a patient is unable to sustain adequate spontaneous gas exchange, or if in the course of therapy, the patient’s ability to maintain adequate gas exchange (e.g., due to the use of medications) is compromised or eliminated, one of these four methods must be employed successfully to assure survival. They constitute the four dimensions of airway management. Hence, the assessment for anticipated difficulty should focus on these four independent operations:

• 
  

  Difficult BMV

  
  
• 
  

  Difficult laryngoscopy and orotracheal intubation (direct laryngoscopy [DL] or video-laryngoscopy [VL])

  
  
• 
  

  Difficult EGD

  
  
• 
  

  Difficult surgical airway

Ordinarily mask-ventilation and orotracheal intubation are the usual methods employed in managing the airway of patients unable to adequately breathe for themselves. If a difficult airway is anticipated, and it is not to be managed “awake,” EGDs and surgical airway techniques are usually considered rescue options. Importantly, they ought not be considered “defacto” evidence of “failure” if they are “part of the plan,” a fundamental concept advanced in this text. Techniques under consideration as first line or back up depend in large part on the context of the situation such as the condition of the patient, the skill of the practitioner, the availability of skilled assistance, the location and equipment available, and the time of day (see Chapter 7: Context Sensitive Airway Management).

Acute care practitioners ought to be able to determine whether or not a patient is adequately ventilating and oxygenating on their own and whether or not they will be able to sustain adequate respiration in the near term (i.e., What is the anticipated clinical course over the next minutes to hours?). It is therefore only reasonable to expect that if an airway practitioner is to intervene in such a manner that spontaneous ventilation is to be compromised (e.g., a neuromuscular blocking agent [NMBA] is to be used), the practitioner must also be able to predict that an alternative artificial method of effecting ventilation will be successful.

In elective situations, difficulty with mask-ventilation is uncommon. Langeron et al.² was the first to address the issue of codifying “difficult mask-ventilation” (DMV) prospectively reviewing the management of 1502 patients undergoing elective surgery under general anesthesia. DMV was defined as:

1. 
   

   an inability to maintain SaO₂ greater than 92% while using 100% O₂ via the anesthesia circuit bag-mask unit;

   
   
2. 
   

   significant gas leak around the face-mask;

   
   
3. 
   

   a need to increase the fresh gas flow to rates greater than 15 L·min⁻¹ and to use the flush valve more than twice;

   
   
4. 
   

   no perceptible chest wall movement during ventilation;

   
   
5. 
   

   the need to perform a two-handed mask technique; or

   
   
6. 
   

   changing the practitioner.

The anesthesia practitioner was asked to identify ventilation as difficult only if the difficulty was perceived to be clinically relevant, that is, potentially leading to a patient threat. In 5% of the patients ventilation was considered difficult, and in only one patient was ventilation impossible. Following multivariate analysis, five criteria were recognized as independent factors for DMV: age more than 55 years; BMI greater than 26 kg·m⁻²; lack of teeth; presence of a beard; and a history of snoring (see section “Difficult BMV: MOANS ” in Chapter 1).

Kheterpal et al.^3,4 confirmed that obesity (BMI >30 kg·m⁻²), snoring and sleep apnea, age (>56 years), and Mallampati of Grade III or IV were risk factors for difficult ventilation and, in addition, noted that a history of radiation therapy to the neck and severely limited jaw protrusion predicted difficult BMV (see Chapter 8 for a detailed discussion). Han⁵ and Kheterpal³ proposed DMV scales for the purposes of clarity and communication (see Tables 2–1 and 2–2).^5,3

DMV in patients under general anesthesia is likely to occur in 2% to 5% of patients and impossible mask-ventilation on the order of one event per thousand anesthetics.^2,3,6

In the emergency situation, other factors may become relevant when considering whether difficulty with mask-ventilation is more likely to be encountered. Trauma to the face with resultant edema, bleeding or debris in the airway, and the need to maintain in-line C-spine immobilization when required may increase the degree of difficulty with mask-ventilation. In addition, the use of cricoid pressure, often perceived to be necessary in emergency intubations, is recognized to increase the likelihood of DMV. Petito and Russell⁷ evaluated the impact of cricoid pressure on lung ventilation during BMV. Fifty patients were randomized to either with or without cricoid pressure applied during a 3-minute period of standardized mask-ventilation. Patients who had cricoid pressure applied were considered more difficult to ventilate (36% vs. 12%), and these patients tended to have more air in the stomach than those patients considered easy to ventilate without applied cricoid pressure.

Most of the studies dealing with assessment of the airway in anticipation of tracheal intubation using a laryngoscope have limited applicability to currently available alternative devices (e.g., rigid endoscopic devices, intubating EGDs, and video-laryngoscopes).^8–10 Modification of Mallampati’s original schema¹¹ as well as alternate strategies to assess the airway (see section “Difficult DL Intubation: LEMON” in Chapter 1) have been proposed. These have ranged from using simple anatomical descriptors, ranking and summating anatomical scoring systems, and using logistic regression to create predictive scales to derive performance indices. These strategies share some common characteristics: they have high sensitivity but low specificity and low positive predictive value with respect to predicting failure. For example, Shiga et al.¹² employing a meta-analysis to assess combined Mallampati and temperomandibular joint displacement scores found a positive association with difficult intubation of only 9.9%. Additionally, many of the tests have only moderate inter-observer reliability.^13,14 Such limitations may help to explain why these tests often fail to predict difficult tracheal intubation, and why perhaps some practitioners question the ability of preanesthetic airway assessments to accurately and with certainty predict or rule out difficulty.¹⁵

A number of new schemes and techniques used to predict potential airway difficulty have been described; their accuracy and widespread applicability are not yet determined. However, it is likely that they will have a low positive predictive value, similar to current strategies, because of the low incidence of airway difficulty.^15,16 Furthermore, we know that even with careful evaluation, difficulty will not be predicted in many instances.^16,17 Therefore, strategies to manage the unanticipated difficult airway should be preformulated and practiced to minimize adverse outcomes resulting from the inevitable occurrence of false-negative predictions.

How Is Airway Management in an Emergency Setting Different?

Airway management in an emergency setting may be complicated by a multitude of factors. Trauma to the face and neck may distort anatomical features or obscure them with blood and debris. Additionally, blood in the airway may absorb a significant amount of the light cast by airway devices making recognition of anatomic features more difficult. The requirement for in-line stabilization in patients with spinal injury or perceived to be at-risk for a spinal injury may make DL more difficult.¹⁸ Unprepared patients are often associated with a full stomach and are at a higher risk of regurgitation and aspiration of gastric contents. The controversy regarding cricoid pressure has been debated and a rational statement based on the current state of evidence published by the Canadian Airway Focus Group (CAFG), echoing an editorial by Ovassapian in 2009.^19,20 These statements take into account that the evidence supporting the use of cricoid pressure is observational only. There is evidence that the maneuver imposes an element of obstruction to the passive regurgitation of gastric contents²¹ and anecdotal evidence that it has prevented aspiration.^22,23 On the other hand it has been shown to be difficult to teach and perform,²⁴ may not protect against aspiration in all patients at risk,^25–27 and hinders BMV, EGD insertion and ventilation, and tracheal intubation.^28–30 Even a recently published Cochrane Review is unable to resolve the controversy as to whether cricoid pressure should or should not be abandoned in high-risk patients.³¹

The position of the CAFG is as follows: “As cricoid pressure is likely to have potential benefits, its continued use seems prudent during rapid sequence intubation in the patient at high risk of aspiration (strong recommendation for, level of evidence C). However, if difficulty is encountered with face-mask-ventilation or tracheal intubation, or if EGD insertion is needed, progressive or complete release of cricoid pressure is justified.”²⁰ The removal of cricoid pressure may improve the view obtained at laryngoscopy and seems unlikely to make the view worse. Harris et al.³² reported the experience of 402 pre-hospital emergency anesthetics and noted that, in settings where the application of cricoid pressure was associated with poor laryngeal view, removal of the pressure resulted in improved view in 50% of patients. In the remainder, there was no improvement in view and other measures (BURP or laryngeal manipulation) were employed in an attempt to improve the view and did so in about two-thirds. In no patient was the removal of cricoid pressure associated with a worse view.

Emergency situations and hemodynamically unstable patients may contraindicate the use of drugs to facilitate laryngoscopy, resulting in intubating conditions which may be less than ideal. Finally, a chaotic emergency environment may distract the practitioner, making it more difficult to manage the airway.

What Does Experience Tell Us About Rescuing the Difficult Airway?

Evidence has emerged that having automatic default-to strategies improves the success of rescue airway interventions and reduces the occurrence of adverse outcomes.³³ Conversely, there are also data demonstrating that persisting with failing techniques rather than defaulting to rescue strategies results in higher rates of morbidity and mortality.^34,35 Rose and Cohen¹ reported that difficult laryngoscopy in anesthesia practice was most often managed with persistent attempts at DL, and the use of alternative approaches to tracheal intubation was uncommon. In these patients, there was a higher incidence of desaturation, esophageal intubation, dental damage, and unexpected ICU admissions. Similarly, Mort,³⁶ in reviewing the airway management of 2833 critically ill patients outside of the operating room, noted that the most common strategy implemented for managing difficult intubations was, again, repeated DL. There was a significant increase in the rate of airway-related complications as the number of laryngoscopic attempts increased (≤2 vs. >2).^36,37 These complications included hypoxemia, regurgitation, aspiration, bradycardia, and cardiac arrest.^36–38

Contrary to the experiences reported by Rose and Cohen and Mort, Hung et al.³⁹ noted that immediately choosing an alternate technique (e.g., a lightwand device) when DL had failed was typically rewarded with rapid tracheal intubation. Complications were both rare and minor and generally attributable to the preceding attempts at DL. Heidegger et al.⁴⁰ reported on a protocol for management of both anticipated and unanticipated difficult intubations that emphasized defaulting to the flexible bronchoscope early when difficult laryngoscopy was anticipated or observed. Applied in 13,248 intubations, the protocol failed in only six patients (0.045%); again this strategy was associated with minimal morbidity. Similarly, Combes et al.⁴¹ reported on the efficacy of an institutional protocol employing the intubating laryngeal mask and a “bougie” (Eschmann Tracheal Introducer). One hundred cases of unanticipated difficulties occurred among 11,257 tracheal intubations. There were three deviations from the protocol and two patients were awakened without further airway management. The tracheas of all patients managed by the protocol were successfully intubated and ventilated. Finally, Mort⁴² compared the outcomes of patients undergoing emergency tracheal intubation in his institution before and after the application of the American Society of Anesthesiologists (ASA) guidelines. The rate of cardiac arrest during emergency intubation was reduced by 50%.

Connelly et al.⁴³ noted that alternatives to DL were far more likely to be successful than persistent use of DL in setting of multiple failed attempts.

It is clear that early conversion to adjuncts and alternatives to direct-vision laryngoscopy when DL proves difficult results in a higher salvage rate with low patient morbidity than persistent use of the direct laryngoscope. The evidence is that the choice of the alternative may be less important than the fact that it is a practiced alternative and chosen early in a planned approach when DL has proven to be difficult or has actually failed.

Is There a Pattern to the Way Airway Practitioners Behave in the Face of a Difficult or Failed Airway?

Tracheal intubation is still predominantly performed orally under DL. Difficulties related to airway management largely involve failure to achieve tracheal intubation due to difficult DL. A number of innovative new tools for tracheal intubation have been presented in recent years, which address many of the factors that give rise to difficult DL.⁴⁴

The direct laryngoscope is designed to facilitate tracheal intubation by establishing a line-of-sight from the mouth to the larynx. As has already been noted, there are multiple patient factors, which individually or in combination may conspire to obstruct a laryngeal view. The ability to predict all patients in whom it will be impossible to establish a line of sight during laryngoscopy is sufficiently imprecise that sole reliance on the laryngoscope to perform tracheal intubation is a precarious strategy.

It is likely that reliance on limited conventional airway techniques is a risk-enhancing behavior, which predisposes patients to increased rates of morbidity and mortality. There is evidence that such behavior has been common among anesthesia practitioners. Rosenblatt et al.⁴⁵ surveyed a random sample of the active membership of the ASA. The survey presented difficult airway scenarios involving cooperative adult patients who required tracheal intubation and physicians were asked to identify their preferred management technique. In a scenario described as a patient with a history of previous difficult intubation, 60% of practitioners would induce general anesthesia and 59% would proceed with DL. Experienced practitioners tended to use higher risk induction techniques and were more likely to use the laryngeal mask airway (LMA) in situations commonly agreed to be unconventional or contraindicated. Use of alternative devices including the Bullard laryngoscope, a lightwand, and other adjuncts was uncommon, occurring in less than 5% in all scenarios.

Jenkins et al.⁴⁶ surveyed 833 Canadian anesthesiologists to assess difficult airway management, training, and access to airway equipment. Respondents were asked to indicate their management choices in 10 difficult airway scenarios. DL was the preferred technique overall, with the flexible bronchoscope being the second most commonly used device. More experienced, male, and older practitioners were more likely to choose asleep induction for high-risk scenarios, a finding similar to that of Rosenblatt. Respondents were not asked to indicate their degree of comfort in using the alternatives that were chosen to manage the clinical scenarios described in the survey. Wong et al. surveyed Canadian anesthesiologists by mail regarding their management preferences in two situations: difficult intubation and cannot intubate, cannot ventilate (now more commonly referred to as cannot intubate, cannot oxygenate [CICO]). In the difficult intubation scenario, the preferred alternative airway devices were lightwand (45%), flexible bronchoscope (26%), and intubating LMA (20%). Only 57% of respondents had encountered a CICO situation in real life. In the CICO scenario, preferred invasive techniques were needle cricothyrotomy (51%), open cricothyrotomy (28%), and tracheotomy by surgeon (14%). In general, anesthesia practitioners had little experience with and were uncomfortable with open surgical airways, although those that had practiced on mannequins were more comfortable using them in patients.⁴⁷

There has also been a substantial change in our thinking with respect to surgical airway management as presented in Chapter 1. To review, in the past it was left to the airway practitioner as to whether to perform a Seldinger technique or an open cricothyrotomy. In fact, it was taught that anesthesia practitioners ought to preferentially select a Seldinger technique as using a needle as opposed to a scalpel was felt to be psychologically more acceptable. However, Lamb,⁴⁸ Aslani,⁴⁹ and Elliot⁵⁰ demonstrated that fellowship trained and certified anesthesiologists cannot reliably locate the cricothyroid membrane in elective surgical patients, particularly if they are female or obese. Subsequently, the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society (DAS) in the United Kingdom (NAP4)^34,35 identified that needle techniques were often unsuccessful and open techniques were more successful, although in many instances in the NAP4 reports, surgeons were more likely than anesthesia practitioners to perform the open techniques. It is currently recommended that an open cricothyrotomy be performed in the CICO situation or that, in the event of problems with needle techniques, conversion to an open technique take place.^34,51 It is recognized that most anesthesia practitioners would likely be neither trained nor competent to do so at this time.

Cricothyrotomy employed in the setting of a failed airway has become emblematic of airway management failure. It is now taught that if the airway practitioner considers a CICO situation even remotely possible that the cricothyroid space be identified and the incision line marked preemptively. In other words, should a cricothyrotomy be needed it is a deliberate “part of the plan” as opposed to “emblematic of failure.” The psychology of this approach is compelling in motivating individuals to move earlier to a cricothyrotomy as soon as a CICO situation is identified. Analysis of the 2005 ASA Closed Claims Database and NAP4 identified delay in performing cricothyrotomy as substantial issues leading to poor outcomes.^34,35,52

Kristensen and Moller⁵³ similarly assessed airway management behavior, experience, and knowledge among Danish anesthesiologists by surveying all members of the Danish Society of Anesthesiologists. Respondents were asked if they had experienced situations during anesthesia in which insufficient oxygenation had caused serious problems that could have been prevented by different airway management. About a quarter of those surveyed answered in the affirmative with 20% of registrars and 26% of specialists agreeing. When asked whether they would perform awake intubation if they expected a difficult intubation, 34% of registrars, 50% of senior registrars, but only 25% of specialists said that they would. Only 48% of registrars and 59% of specialists agreed that a previous difficult intubation was a reliable predictor of difficult intubation in the future. These high-risk attitudes and behaviors are especially concerning. Among the specialists, only 21% use a lightwand at least once a year, 11% a BL, and 7% a retrograde technique. Forty percent of specialists had intubated the trachea of an awake, spontaneously breathing patient 10 times or less in their career, and 23% of specialists had never done so using an FB. Finally, about half the registrars and a third of the specialists reported that they did not routinely have immediate access to an LMA when providing anesthesia.

Ezri et al.’s⁵⁴ more recent survey of American anesthesia practitioners suggests that there may be an increasing willingness to use alternatives to the direct laryngoscope in airway scenarios perceived as high risk. However, Ezri also observed that such willingness persisted even when the anesthesia practitioners acknowledged that they were neither comfortable nor experienced with the alternate technology that they proposed using in these difficult situations.

Finally, although repeated reports in the past cited poor clinical decision making by anesthesia practitioners in the setting of difficult airway (both anticipated and unanticipated) resulting in patient harm, evidence is beginning to emerge suggesting that there has been a change in the approach to airway care on the part of at least a segment of anesthesia practitioners; this change emphasizes greater and earlier conversion to the use of an alternative (emphasizing but not exclusively employing the VL) to the direct laryngoscope in the setting of unanticipated difficult intubation with lesser reliance on multiple attempts with the direct laryngoscope before conversion occurs.⁵⁵ The evidence would also support the conclusion that practitioners with greater experience using video-laryngoscopes achieve greater success with them.

What Is the Medical–Legal Experience with Respect to Airway Management Failure?

The largest series of published medical–legal cases involving airway management is that of the ASA Closed Claims Project. Data from the airway cases reviewed in the ASA Closed Claims Project were originally published in 1990, with additional publications in 1991, 2000, 2005, and 2011.^56–59 In the original (1990) report, respiratory claims accounted for 34% (522/1541) of all claims. Inadequate ventilation was the most common single event overall, accounting for 12.7% of all claims and more than a third of the respiratory claims. In the original report, esophageal intubation and difficult intubation claims occurred each at about half the rate of those for inadequate ventilation.⁵⁶ Caplan et al.⁵⁶ speculated that improved monitoring would reduce the incidence of inadequate ventilation and esophageal intubation and enhanced training would reduce the occurrence of difficult intubation and its sequelae.

In 2000, additional Closed Claims data was published in the ASA Newsletter.⁵⁸ Respiratory claims then accounted for 17.9% of total claims (798/4459), half the original proportion. Inadequate ventilation and esophageal intubation by then had accounted for considerably fewer claims than in the first report but claims for difficult intubation were now responsible for 6.4% of total claims, 14% higher than in the original report. In 48% of the difficult intubation claims, some difficulty was anticipated preoperatively by the anesthesia practitioner. Despite this expectation of difficulties, the most common (69% of instances) management strategy employed in these situations was induction of anesthesia followed by persistent attempts at oral laryngoscopic intubation. A similar strategy of multiple attempts orally was employed in scenarios in which difficulty was not anticipated but encountered. Of the cases in which difficulty was anticipated, 69% eventually deteriorated into a “CICO” situation. Airway management was deemed to be below the accepted standard of care in 49% of the cases reported in the update. This is significantly higher than that seen for other claims in the database.

An updated analysis of the closed claims relating to management of the difficult airway was published in 2005.⁵² Two-thirds of the documented events took place during induction of anesthesia and the remaining third during surgery, extubation of the trachea, or recovery. Care was judged to be less than appropriate or substandard in nearly half of the difficult airway claims. In the claims with an anticipated difficult airway, the first strategy was still more likely to be intubation after induction of general anesthesia with ventilation ablated (61%) than awake intubation (32%). There was no difference in the outcome in claims when succinylcholine was used compared with those in which a non-depolarizing muscle relaxant was employed at induction. Awake intubation was attempted but unsuccessful in 12 claims, resulting in death or brain damage in 75% of these claims. In 5 of these 12 claims, airway difficulties arose when general anesthesia was induced after attempts at awake intubation were abandoned. Finally, in claims in which an emergency airway situation developed, the outcome was worse with persistent attempts at intubation before attempting emergency nonsurgical ventilation or emergency surgical airway access. The final update was provided in 2011.⁵⁹ Respiratory events accounted for 17% of total claims and the most common events leading to claims were difficult intubation, inadequate oxygenation or ventilation, and aspiration. Difficult intubation accounted for 27% of respiratory events reported from 1990 to 2007. Airway injury was the fourth most common injury in claims accounting for 7% of all claims; in previous reviews, unanticipated difficult laryngoscopy and intubation were associated with airway injury.

Cook et al.⁶⁰ reported on the closed claims in the United Kingdom against the National Health Service between 1995 and 2007. Of 841 relevant claims 95 (11%) were related to dental damage, 71 (8%) were associated with airway management (excluding dental damage and 29 (3%) were associated with respiratory events). Defining which cases are, from a medicolegal viewpoint, high risk is uncertain, but the clinical categories with the largest number of claims were regional anesthesia, obstetric anesthesia, inadequate anesthesia, dental damage, and airway. Those with the highest overall cost were regional anesthesia, obstetric anesthesia, and airway, and those with the highest mean cost per closed claim were respiratory, central venous cannulation, and drug error excluding allergy. Although airway claims were relatively infrequent overall, they tended to be associated with some of the most severe outcomes and the highest costs to close.

Claims involving airway management were also more likely to be associated with a permanent adverse outcome than others, and it is recognized that severe adverse outcomes can affect the judgment as to the appropriateness of care.⁵⁹ However, criticism of care may be well founded as a preoperative airway review was not conducted (or recorded as having been conducted) in 25% of cases, 28% of practitioner’s had no explicit plan for dealing with anticipated difficulties, and 25% did not alter their conventional method of airway management despite recognizing the potential for difficulty. Furthermore, when difficulties were encountered, the most common management strategy was persistent nonsurgical attempts at tracheal intubation. In 69% of cases where difficulties were anticipated, a CICO situation arose. Finally, and significantly, no strategy for extubation was outlined in almost half of the cases in which the practitioner encountered difficulties intubating the trachea.⁵⁹

NAP4 in the United Kingdom built on the earlier work of Cook.^34,35 This year long study gathered patient cases of major airway complications in all 309 NHS hospitals in the United Kingdom. It identified cases from the operating room, intensive care unit (ICU), and emergency department (ED). The authors defined major airway complications as those leading to death, brain damage, emergency surgical airway, or unexpected ICU admission. After final review, 184 cases were included: 133 from anesthesia, 36 from ICU, and 15 from the ED. Importantly, when it came to surgical airway, the study identified a high failure rate of percutaneous cricothyrotomy performed by anesthetists. Of 25 attempts, only 9 were successful (36%). An open surgical technique, often performed by a surgeon, was associated with a 100% success rate of tracheal cannulation, although not all patients survived. In total, 14 tracheotomies were accidentally dislodged, all in the ICU, with a 50% mortality. Other important conclusions could be drawn from this landmark study:

• 
  

  poor assessment and poor planning led to poor outcomes!

  
  
• 
  

  if an awake intubation was indicated, it was a good idea to do it!

  
  
• 
  

  repeated attempts at orotracheal intubation or EGD use were rarely successful, better to perform a surgical airway early!

  
  
• 
  

  it was good to plan for failure!

  
  
• 
  

  failure to detect carbon dioxide meant that the endotracheal tube was not in the trachea, even in the newly dead!

  
  
• 
  

  and inhalation induction of anesthesia on adult patients with upper airway obstruction was a bad idea!

So we are not alone in North America!

Why Are Algorithms Useful in Airway Management?

Automatic responses are not typical when we are confronted by rare events such as the “CICO” situation, or even many types of emergency airways. Therefore, fundamental to successfully managing the emergency or failed airway is the development of a systematic approach to clinical situations rarely encountered in day-to-day practice. Algorithms, decision trees, and mnemonics feature prominently in these approaches and they must be evidence based and quickly and easily applied. It is fair to say that after years of formal medical education and practice, most of us harbor an aversion to algorithms. While it is recognized that rigidity stifles innovation and constrains personal preference, adherence to sensibly constructed decision trees minimizes variation, conserves valuable time, and has been shown to provide the greatest chance for success.

Decision aids such as algorithms and mnemonics are meant to inform rather than dictate to the practitioner. The practitioner is required to correctly identify the clinical problem (i.e., a failed airway) before choosing the algorithm. The algorithm should be designed and validated to ensure a high degree of success, provided that it is applied in the correct clinical situation. Many of these situations occur relatively infrequently in clinical practice, and it is unlikely that practitioners will have an opportunity to generate rules for managing the situations based on experience alone. By providing a limited number of likely-to-be successful options, the algorithm can increase the likelihood of a good outcome.

Reason⁶¹ has defined two basic mechanisms whereby practitioners deal with critical incidents. The first is a rule-based solution, whereby on recognizing the event for what it is, one identifies and applies a solution that experience has shown will likely be useful in solving the problem. Recognizing the event involves a process called “similarity-matching”; based on identifying that the characteristics of the events are similar to those of past events (in a sense, pattern recognition). The practitioner then decides upon a particular solution that is likely to be effective in solving the problem and resolving the threat. This presupposes that the practitioner has had sufficient experience with both the situation and the application of the rule to both immediately recognize the problem and to know which rule to apply. This ability constitutes what is called “expertise.” Unfortunately, difficult and failed airways are encountered infrequently in practice, and the individual experiences of practitioners may have not been sufficient to earn them expert status.

The second mechanism for dealing with critical incidents is to apply a knowledge-based solution. This is a ground-up, first-principle strategy whereby the practitioner, without significant past experience with similar situations, attempts to find an appropriate solution. Not surprisingly, such strategies often involve multiple decisions, are time consuming, and when made under pressure of time, are more likely to fail.

Many airway practitioners will not have sufficient experience with difficult and failed airway scenarios to have, of themselves, created a rule-based, organized approach to these airway dilemmas for which knowledge-based solutions may be inadequate. For this reason, preformulated airway algorithms are helpful in these situations and deserve to be considered by all airway practitioners. It is probably safe to say that with the attention paid to airway management by anesthesia, emergency medicine, and EMS over the past two decades, there has been a general reduction in emphasis on algorithms as guides to action, though they remain valuable aids in teaching and learning difficult and failed airway management.

Coincident with the development of the decision trees (strategies) and vital to airway management success is skill in the application of an array of devices and techniques (tactics) that can optimize clinical outcomes. Techniques and devices advocated in this chapter, as in the case of the decision trees, are anchored by evidence and expert opinion, rather than personal preference.

Algorithms meant to guide practice in crisis situations must exhibit the following design elements:

• 
  

  Entry and exit points are easily recognized.

  
  
• 
  

  They are based on the best available evidence.

  
  
• 
  

  Branch points are binary.

  
  
• 
  

  There are a limited number of actions at each step.

  
  
• 
  

  They are easy to remember and represent graphically.

  
  
• 
  

  Not all algorithms are intended as practice guides, rather as a graphic representation of an overall strategy (e.g., the ASA Algorithm).

What Are the Strengths and Weaknesses of the ASA Difficult Airway Algorithms and How Have They Evolved Over Time?

The ASA, in an attempt to avert airway management disasters, has produced the ASA Difficult Airway Algorithm first in 1993 (Figure 2–1), a revision in 2003 (Figure 2–2) and again in 2013 (Figure 2–3).^62–64 All iterations of the ASA Difficult Airway Algorithm are derived from the Practice Guidelines for the Management of the Difficult Airway, developed by the ASA Task Force on Difficult Airway Management.

In all three iterations, Panel A is directed at anticipating and managing the difficult airway, and Panel B deals with the failed airway. The algorithms guide management strategies when difficulty is predicted and recommend rescue tactics in the event of failure. They emphasize the importance of possessing expertise in more than one airway management technique and that each time an airway is managed, the practitioner formulate a variety of backup plans should the primary plan fail (Plan B and Plan C).

As the ASA guidelines evolved from the first to the second iteration, a number of important changes were made. Guidance was offered to those anatomic elements that may prove useful in the evaluation of the airway (Table 2–3), although no direction is given as to how to interpret the findings. The concept of a reassuring versus non-reassuring assessment was now included, with the recommendation that a non-reassuring assessment be a relevant factor in the construction of a plan for airway management. The need for the continuous application of oxygen to the patient during management of the difficult airway was emphasized in the second iteration. Finally, the LMA for ventilation was moved from the emergency pathway of Panel B to an entry point determining whether the emergency pathway is entered. This change was likely due to the worldwide recognition that the LMA is an effective rescue device.

The third iteration evolved somewhat further. The term LMA was replaced by the noncommercial term, supraglottic devices (SGD which has been used interchangeably with EGD by others). While the overall arrangement and construction of the 2013 algorithm is very much the same as the 2003 Algorithm, there are substantive issues mentioned in the narrative:

• 
  

  The disclaimer that this guideline is not meant to represent the standard of care is reiterated as the ASA does for all of their guidelines.

  
  
• 
  

  It is clarified that this guideline applies to anesthesia practitioners and those supervised by anesthesiologists.

  
  
• 
  

  It is clarified that this guideline only applies during the conduct of an anesthetic, and by exclusion not to anesthesia practitioners called to manage airways outside the OR.

  
  
• 
  

  An extubation strategy is recommended.

  
  
• 
  

  VL is mentioned in the guidelines.