Management of the Unanticipated Difficult Airway
Fran D’Ercole, MD
Professor of Anesthesiology
University of North Carolina at Chapel Hill School of Medicine
Chapel Hill, North Carolina
The focus of this article is on methods to better understand the variables and triggers involved in the management of the unanticipated difficult airway that defaults to an emergency surgical airway.
As a physician-anesthesiologist, I can offer unique personal insights following the submission of a “can’t intubate, can’t ventilate” (CICV) case that was entered into the Anesthesia Quality Institute (AQI) database. After the AQI submission, the case study was published as a case report titled “Knife or Needle—A Need to Act!”1
A 71-year-old woman with severe obesity and continuous positive airway pressure (CPAP)-dependent sleep apnea presented for elective gynecologic surgery. The patient’s surgical history from 10 years earlier was unremarkable for anesthesia complications. However, the patient had since gained significant weight, and the need for CPAP was relatively recent.
Induction was smooth and uneventful, with IV fentanyl, lidocaine, and propofol. Mask ventilation was attempted successfully. Rocuronium was administered. Direct laryngoscopy was performed with a Miller 2 blade offering a grade 3 glottic view. Mask ventilation was reattempted and a GlideScope (Verathon) video laryngoscope (VL) was requested. Although the VL provided a grade 1 view, the intubation attempt with a 7.0 styletted endotracheal tube (ETT) failed.
Another attempt was made using the VL combined with an elastic boogie; however, the glottis view diminished to grade 2. Intubation was unsuccessful, and the anesthesia care team made the decision to let the patient emerge from anesthesia. However, mask ventilation became increasingly difficult, until the ability to provide ventilation ceased. The anesthesiologist attempted to combine video laryngoscopy with a fiber-optic scope, yielding a grade 4 view, but laryngeal edema was evident and the fiber-optic scope was unable to pass through the vocal cords.
Placement of a rescue laryngeal mask airway (LMA, Teleflex) was tried but ventilation was not possible. Ear, nose, and throat (ENT) surgical backup was requested but was not immediately available. The cricothyroid membrane (CTM) was not palpable secondary to obesity (and associated neck pannus).
The anesthesiologist incised the neck until the tracheal rings were deeply palpated, and a second incision was made between two palpable tracheal rings. A 5.0-mm ETT was placed successfully into the trachea, as confirmed by end-tidal carbon dioxide (EtCO2). The CTM was not appreciated.
Subsequent surgical exploration confirmed a “clean” tracheostomy between the first and second rings, requiring no revision. The patient recovered and was neurologically intact. This was the anesthesiologist’s first surgical airway, but the anesthesiologist had gained experience previously by assisting trauma surgeons in other emergency airway cases.
Larson and Hagberg et al reviewed the case and provided insight into the need to preserve neurologic outcome, which required immediate decision making.2,3 The actions by the anesthesiologist were influenced by a variety of factors, which included more than 22 years of clinical experience, awareness of alternatives to the immediate situation, and the absence of appropriate personnel. There was no surgeon available on-site.
Decision making also was influenced by a previous event that included creating a surgical airway in a patient who experienced an anaphylactic reaction while in a CT scanner after IV administration of iodine-containing contrast. Although this was a different scenario that was not associated with an anesthetic induction, both cases warranted the application of the emergency airway algorithm to its end point.4 The author also attributed her decision making to a study by Cook et al5 and the 4th National Audit Project (NAP4).
One question that often resurfaces during anesthesia induction is the pros and cons of whether to emerge immediately or to readminister short-acting paralytics.
Simulation Provides Experience
As experienced anesthesiologists continue to fine-tune their response times and rescue techniques, the bridge between the experienced and the novice clinician is being forged by simulation.6,7
The reason that some anesthesiologists will use triggers to perform an emergency surgical airway versus employing temporizing techniques may be purely circumstantial. For example, if there is no ENT surgeon or general surgeon in the immediate vicinity, what choices exist for any anesthesia provider? This was especially true for the author, who strongly emphasizes the need for situational awareness and logistics evaluation. This includes early consideration of the availability of surgical consultants, should the need arise.
Calling for assistance and requesting help is part of the emergency airway algorithm.4 However, when assistance is not obtained within a reasonable amount of time, the decision to quickly explore other alternatives is unavoidable. The idea of jerry-rigging jet ventilators attached to an oxygen source while maintaining a positional angiocatheter at the level of the CTM, which hopefully will not kink within the lumen of the trachea, may be merely temporizing. Hope is not a plan or a solution.
Such equivocation may be a bridge to establishing a surgical airway. Temporizing to establish oxygenation to prevent anoxia or prevent progression to cardiac arrest is not the same as establishing an airway. Cardiac arrest with loss of perfusion to vital organs ultimately places the patient at risk for profound hypoxia and loss of neurologic function.
The next important challenge is identifying the CTM. Recently, it was observed by both Hiller et al8 and Law9 that there are deficiencies in the ability to identify the CTM by surgeons, including trauma surgeons and anesthesiologists.
The final step in obtaining an emergency airway in a failed CICV scenario is by percutaneous surgical cricothyrotomy or tracheostomy. The NAP4 study, conducted in the United Kingdom, strongly suggested proceeding to a surgical airway.5 The procedure has a low frequency of occurrence and a high complication rate. Conversely, consider the scenario of the percutaneous technique requiring jet ventilation, which would need to be immediately available and requires advance preparedness. First, the jet ventilator should be preattached to an oxygen source in the operating room prior to anesthesia induction. Second, placement of a needle or angiocatheter in a thick neck may or may not be achievable due to body habitus.
Often, after an angiocatheter is placed successfully within the lumen of the trachea, the proceduralist will be unable to maintain catheter position during attachment to the jet ventilator. The first attempt at jet ventilation is therefore ineffective. This scenario is perceived as a failed attempt with a critical time delay, followed by the obvious need to progress to the surgical airway. The surgical airway in the context of a thick, bull neck is technically challenging, even for an experienced surgeon.
Ultrasound Modalities in Airway Management
Anesthesiologists who are inherently familiar with ultrasound modalities for use in vascular access and regional anesthesia techniques continue to expand the use of ultrasound in airway management. Kristensen and Teoh10 have described standardized ultrasonography techniques to identify the CTM and relevant structures for bedside airway management.
The utility of ultrasound as a fundamental tool in airway management is practical, especially for anesthesiologists who are familiar with the technology, and because ultrasound machines in anesthetizing areas are easily transportable.10 Kristensen and Teoh10 proposed that anesthesiologists managing difficult-airway patients should identify the CTM before proceeding with the delivery of anesthesia. In patients whose CTM is not easily visible or palpable, ultrasonography is an ideal method for locating the CTM.10 Once located, the CTM can be marked with a pen and quickly reidentified in the rare event that difficult airway management results in emergent surgical cricothyrotomy. Instructive airway ultrasound videos are available (www.airwaymanagement.dk/?ultrasonography-in-airway-management).
Attaining competence by a hands-on exam during routine brachial plexus block or central vascular access may increase this important new skill by gaining familiarity with ultrasound imaging of the CTM, tracheal rings, and pleural space. Ultrasound identification of the CTM has been studied in cadavers, especially those with poorly defined neck anatomy.11
Siddiqui et al11 reported a study that found that ultrasonography, compared with digital palpation, increased the probability of correct insertion of the Portex cricothyrotomy device via the CTM by 5.6 times and decreased the incidence of moderate to severe injuries 3-fold in cadavers with difficult or nonpalpable anatomic landmarks. Formalin-fixed cadavers, which do not reflect normal tissue characteristics, were used in this study; nonetheless, it may be argued that in a cohort of patients with difficult or nonpalpable landmarks, ultrasound guidance may lead to faster localization, increased accuracy, and less injury when performing emergency cricothyrotomy.
Effect of the Vortex Model
Following a failed intubation attempt, the mask–LMA–knife phrase proposed by Lown12 reinforces the belief that there are only 3 ways to establish an airway. Failure to establish the airway then progresses to an emergency surgical airway. The Vortex Approach13 provides circular imagery to apply options for nonsurgical airways in any sequence. The vortex model is a 3-D tool that is color-coded with visual prompts. It is not intended to be referred to during an airway crisis but rather is used during training to retain concepts, in a process described as “conceptual imprinting.”
There is an important prompt in the green zone of the vortex encouraging situational awareness and the opportunity for the team to have a timeout. This “airway timeout” is triggered whenever oxygen saturations and alveolar oxygen delivery have been restored. The purpose of the pause is to make a plan, reassemble resources, and call for additional assistance before reinstrumenting the airway. This may prevent the momentum leading to repetitive instrumentation followed by conversion to a CICV situation.
Experience has shown that the vortex tool used in a simulation setting improves recall under stress.6,13 However, Lown12 expressed reservations, believing that use of the complex vortex airway management diagram during a time of extreme stress actually may result in cognitive overload and delay in completing the difficult task at hand. The anesthesia provider responsible may end up being cognitively challenged, and emotionally and technically overwhelmed. The Vortex Approach employs a team concept encouraging everyone to collectively suggest rescue strategies, in a structured manner using a simple visual template.
The major purpose of the vortex model is to avoid the need for surgical airway intervention by suggesting efficient optimal attempts at each of the nonsurgical techniques, by prompting 5 categories of strategies listed on the vortex tool.
In the January 2017 issue of Anesthesiology News, Aditee Ambardekar, MD, described a positive application of the Vortex Approach in simulations with novice medical students who are not yet tasked with decision making.6
Applications for Simulation in Medical Training
Simulation has been used to acquire skills that can be classified into 3 types to form a skills triangle: affective, cognitive, and psychomotor (Figure 1). Affective skills include interpersonal skills, such as the teamwork needed in interacting with other people. Cognitive skills include the application of knowledge, decision making, strategy, and risk assessment. Psychomotor skills involve manual dexterity, hand–eye coordination, and spatial relationships.
The simulation triangle14 used in health care includes biological simulation (standardized human patients or actors), physical simulation (such as mannequins), and virtual simulation (computer-based, without tangible physical elements). A mixed simulator contains both physical and virtual elements. Mixed reality is sometimes referred to as augmented reality. This kind of reality differs from virtual reality in that the focus of the interaction of the performed task lies within the real world instead of the digital environment of virtual reality.15
Computer-based augmented reality applications (ARAs) are increasingly used to support the training of medical professionals. The utility of ARAs are of real interest to medical education because they blend digital, often interactive overlays with the physical learning environment.15 Some ARAs have been designed to provide training for neurosurgical procedures such as ventriculostomy, aneurysm clipping, trigeminal rhizotomy, and thoracic pedicle screw placement.15
Other examples are laparoscopic tasks in minimally invasive surgery and simulator training using a mannequin for transesophageal echocardiography. The use of ARAs has great potential for training medical personnel, as ARAs are digital applications that blend layers of the virtual and physical environment in such a way that an immersive, interactive environment is experienced.15
What makes some anesthesiologists follow through to the end point of the airway algorithm while other anesthesiologists do not—even knowing the consequences of not acting? During the airway emergency that I described, I had the foresight to pre-prep the patient’s neck with betadine approximately 7 to 10 minutes before the final decision requesting a 15-blade. The anesthesia care team, which included the author and 4 experienced certified registered nurse anesthetists, rotated between 2-man bag–mask–valve (BMV) ventilation and video laryngoscopy and rescue laryngeal mask, awaiting emergence.
During this 10-minute period, the most important monitor was capnography. Capnography waveforms came and went and showed us whether effective ventilation was ongoing. Eventually, the capnography waveforms completely ceased, and the situation had progressed to CICV. Opting for no action meant the patient would ultimately progress to cardiac arrest or hypoxic encephalopathy. At that point, there was no other choice to be made—so, “knife please.” I attributed implementation of the emergency airway algorithm through to its end point as the culmination of 2 decades of experience, including participation in the aforementioned previous emergency surgical airway with associated anaphylaxis to contrast media in the venue of a CT scanner.
Anesthesiologists continue to try to understand how human factors affect the ability to act. We need to continue to explore how human factors can play a key role in the decision-making process that allows us to continue up to the end point of the airway algorithm.16
A study looked at the age of anesthesiologists and their patient outcomes.17 It is important that older anesthesiologists use their accumulated experiences and processes to teach younger providers through mixed simulation.
Recreating the reality during a CICV simulation, merging both the 2-D and 3-D vortex, may have limitations as a teaching model. However, ARAs used in mixed simulation may be the best model to recreate the reality necessary to teach important airway skills, formally achieved only through years and decades of clinical experience. According to Lampotang et al, by combining the best of virtual and physical simulation, mixed simulation represents the next generation of patient simulators and training tools, and holds the promise of further heightening patient safety by enhancing cognitive and psychomotor skills during medical procedures.18
Closed Claims Review: The Airway Truly Comes First
Posner and Caplan19 described how adverse respiratory events in the American Society of Anesthesiologists (ASA) Closed Claims Project have constituted the single largest source of injury over several decades: the 1970s to the 2000s. Three mechanisms of injury accounted for almost two-thirds of all claims (n=1,928) for adverse respiratory events. These mechanisms were inadequate ventilation (24% of cases), esophageal intubation (12%), and difficult intubation (24%). In the 1990s, pulse oximetry and EtCO2 were adopted as monitoring standards; inadequate ventilation (18%) and difficult intubation (28%) remained the most common adverse respiratory events, but esophageal intubation (5%) had decreased greatly compared with earlier decades.19
Respiratory event–related claims were—and still are— characterized by a high frequency of devastating outcomes and costly payments. Additional evidence shows that monitored anesthesia care can be more risky than general anesthesia. The ASA Closed Claims Project revealed that severe neurologic injury is more common with monitored anesthesia care than with general anesthesia, especially during deep sedation in cases of unrecognized apnea, when capnography is not employed to verify ventilation. The use of pulse oximetry alone is an inadequate monitor because of the lag time for a desaturation event.
The ASA Difficult Airway Algorithm4 has been modified to include VLs and supraglottic airways (laryngeal masks or Combitube [Medtronic]). However, a supraglottic airway used as a successful bridge to restore the airway does not ensure a secure airway. Petersen et al20 described in a closed claims analysis how a variety of rescue techniques were used, and all of them were associated with poor outcomes. The list included the Combitube, retrograde techniques, jet ventilation, and needle cricothyrotomy without jet ventilation. Jet ventilation caused subcutaneous emphysema, pneumothorax, or pneumomediastinum in 89% of the claims.20 The only change in improvement for rescue techniques was due to the use of the LMA during 1993 to 1999, compared with 1985 to 1992.20
In a recent issue of Anesthesiology, Hilary Grocott, MD, wrote of the “pendulum swing” from the percutaneous needle to the scalpel.21 In addressing this controversy, Takashi Asai, MD, PhD, stated that the “evidence is still insufficient to conclude which method of cricothyrotomy is more reliable than another (and thus it is too early to dismiss [the] percutaneous method yet).”21 Dr. Asai added that, “nevertheless, the current state of knowledge indicates that surgical cricothyrotomy is more reliable than percutaneous cricothyrotomy as a rescue method in [a] cannot intubate, cannot oxygenate situation.”22
The time is now to establish a standardized airway crisis management system and to undergo training on a regular basis to rescue patients from hypoxic damage.23 The ASA Airway Task Force will need to continue updating current algorithms, possibly incorporating models that have already been implemented in other international algorithms. One example may include the 3-D Vortex Approach, which has been gaining preference as an airway cognitive tool.13
Training in advanced cardiovascular life support and pediatric advanced life support are other examples of established training systems. Crisis management in the aviation industry is firmly established and reinforced by regular training. It has been proposed that reliance on simulation is the next step in establishing regular training in difficult airway management that requires a surgical airway.
The study by Heymans et al suggests that the delay in decision making is centered on reluctance to use a scalpel for an emergency cricothyrotomy; however, establishing regular training would prevent such delays and increase success rates to as high as 95%, even when performed by novices.7,23 Recently, Lampotang et al described mixed simulation and applications for ultrasound-guided regional anesthesia procedures, adding a simulated physical ultrasound probe tracked with a magnetic sensor and real-time ultrasound imaging based on the position and orientation of the probe.14 There is the potential that this simulator may have an application as an ultrasound survey of the airway to improve the success rate.
Competence in rescue management of a rare event cannot be gained just by experience; it necessitates training. Applications from both 2-D and 3-D vortex models applied during the CICV scenario using mixed simulation may be an opportunity to enhance medical training. The capability of recreating the reality is necessary to teach important airway skills—formally achieved only through decades of clinical experience—and may help close the performance-knowledge gap. Closing this gap may bring us closer to teaching optimal airway guidance, especially in obtaining successful emergency surgical airways swiftly and reliably. Regarding closed claims reviews, we must do better!
Acknowledgment: Thanks to Marjorie Stiegler for her influence and support of the AQI case report (reference 1).
- Dutton RP. A case report from the Anesthesia Incident Reporting System. Case 2013-10: knife or needle—a need to act! ASA Newsletter.2013;77(10):50-51.
- Larson P. Letter to the editor. ASA Newsletter. 2014;78(2):63.
- Hagberg C, Hiller K, Cattano D. Letter to the editor. ASA Newsletter. 2015;79(6):77.
- Practice guidelines for Management of the Difficult Airway: an update report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology. 2013;118(2):251-270.
- Cook TM, Woodall N, Frerk C. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth. 2011;106(5):617-631.
- Crist C. Knowledge retention in medical students for ASA algorithm and Vortex. Anesthesiology News. 2017;43(1):14,16.
- Heymans F, Feigler G, Graber S, et al. Emergent cricothyrotomy performed by surgical airway naïve medical personnel: a randomized crossover study in cadavers comparing three commonly used techniques. 2016;125(8):295-303.
- Hiller KN, Karni RJ, Cai C, et al. Comparing success rates of anesthesia providers versus trauma surgeons in their use of palpation to identify the cricothyroid membrane in female subjects: a prospective observational study. Can J Anaesth. 2016;63(7):807-817.
- Law JA. Deficiencies in locating the cricothyroid membrane by palpation: we can’t and the surgeons can’t, so what now for the emergency surgical airway? Can J Anaesth. 2016;63(7):791-796.
- Kristensen M, Teoh W. The ultrasound probe in the hands of the anesthesiologist: a powerful new tool for airway management. Anesthesiology News: Guide to AirwayManagement. 2013-2014: 23-30.
- Siddiqui N, Arzola, C, Friedman Z, et al. Ultrasound improves cricothyrotomy success in cadavers with poorly defined neck anatomy. 2015;123(11):1033-1039.
- Lown N. Can’t intubate, can’t ventilate: “mask – LMA – knife”. Br J Anaesth. 2015;115(1):147-148.
- Chrimes N, Fritz P. The Vortex Approach: management of the unanticipated difficult airway. Smashwords Edition. 2013. vortexapproach.org. Accessed July 7, 2017.
- Lampotang S, Lizadas D, Rajon D, et al. Mixed simulators: augmented physical simulators with virtual underlays. Proc IEEE Virtual Reality. 2013;7-10.
- Barsom EZ, Graafland M, Schijven MP. Systematic review on the effectiveness of augmented reality applications in medical training. Surg Endosc. 2016;30(10):4174-4183.
- Laerdal Medical. Just a Routine Operation. youtube.com/?watch?v=JzlvgtPIof4. Accessed July 7, 2017.
- Liau A, Havidich JE, Onega T, et al. The National Anesthesia Clinical Outcomes Registry. Anesth Analg. 2015;121(6):1604-1610.
- Lampotang S, Lizadas D, Robinson A, et al. Mixed simulators: seamlessly integrating physical and virtual simulation for training in procedural skills and safety. APSF Newsletter. June 2014:29-31.
- Posner KL, Caplan RA. Medical-legal considerations: the ASA Closed Claims Project. Chapter 55; 1-5. clinicalgate.com/?medical-legal-considerations-the-asa-closed-claims-project/?. Accessed July 20, 2017.
- Peterson GN, Domino KB, Caplan RA, et al. Management of the difficult airway: a closed claims analysis. 2005;103(1):33-39.
- Grocott H. As the pendulum swings from the needle to the scalpel, the evolution of emergency airway management will continue. Anesthesiology. 2017;126(2):355-356.
- Asai T. In reply to correspondence. Anesthesiology. 2017;126(2):356.
- Asai T. Surgical cricothyrotomy, rather than percutaneous cricothyrotomy, in “cannot intubate, cannot oxygenate” situation. Anesthesiology. 2016;125(2):269-270.