Difficult Airway Management What´s new?

Difficult Airway Management: What’s New?

By Dr. Carin A. Hagberg, M.D. , Thursday, April 25, 2013
Management of the difficult airway remains one of the most relevant and challenging tasks for anesthesia care providers. There is a 1-3% incidence of unanticipated difficult airways in patients undergoing general anesthesia, possibly up to 18%. Learn more about the latest trends, techniques and guidelines in difficult airway management

Dr. Carin A. Hagberg, M.D. University of Texas Health Science Center at Houston, Anesthesiology Department  

SCOPE OF THE PROBLEM

Management of the difficult airway remains one of the most relevant and challenging tasks for anesthesia care providers.  Claims involving airway management continue to comprise an important aspect of the ASA Closed Claims Project data base.1   There is a 1-3% incidence of unanticipated difficult airways in patients undergoing general anesthesia, possibly up to 18%.  Thus, at a local facility, such as at the author’s, where 25,000 general anesthetics are performed annually; this means there are 250-750 possible unanticipated difficult airways encountered per year.  On an international level, this is a HUGE problem!

Presently, the Fourth National Audit Project (NAP4) of the Royal College of Anaesthetists and the Difficult Airway Society was conducted, a prospective study of airway-related adverse events conducted over a 1 year period (September 2008-2009) of 300 hospitals in the UK.2  Of the 2.9 M patients, there was 184 cases in which major adverse airway events occurred.  Intrinsic patient features accounted for the most frequent causal and contributory factors; the most common extrinsic contributing factors were judgment and training.  Up to 75% of the events could have possibly been averted with better airway assessment and management practices, including better utilization of awake intubation and appropriate use of supraglottic airway devices (SADs).

ASA DIFFICULT AIRWAY MANAGEMENT ALGORITHM

The practice of airway management has seemingly become more complex with time, as evidenced by the introduction of a number of new airway devices, several of which have been included in the American Society of Anesthesiologists (ASA) Difficult Airway Management Algorithm.3  This Algorithm was recently modified by the Task Force on Difficult Airway Management based on an evaluation of the literature published since completion of the first update and an evaluation of new survey findings of expert consults and ASA members.  First and foremost, there was an addition of definitions related to difficult supraglottic airway (SGA) ventilation or placement.

1.            Difficult face mask or SGA ventilation:  It is not possible for the anesthesiologist to provide adequate ventilation due to one or more of the following problems:  inadequate mask or supraglottic airway seal, excessive gas leak, or excessive resistance to the ingress or egress of gas. 

2.            Difficult SGA placement:  SGA placement requires multiple attempts, in the presence or absence of tracheal pathology.  In fact, consideration should be made of difficulty with SGA placement when performing a preoperative assessment.

An assessment of the likelihood and anticipated clinical impact of six basic problems that may occur alone or in combination should be performed:  (1) difficulty with patient cooperation or consent, (2) difficult mask ventilation, (3) difficult supraglottic airway placement, (4) difficult laryngoscopy, (5) difficult intubation, and (6) difficult surgical airway access.

The use of a laryngeal mask airway in the algorithm has been replaced with supraglottic airway (SGA), which may include the intubating LMA and the laryngeal tube.  The Esophageal Tracheal Combitube is no longer specified as an option for emergency non-invasive airway ventilation.  Nonetheless, although the laryngeal tube was included as an alternative SGA, the literature is insufficient to evaluate the efficacy of the laryngeal tube or laryngeal tube suction in providing adequate ventilation for difficult airway patients.

The rigid bronchoscope has also been removed as an emergency non-invasive airway technique. Additionally, retrograde intubation and jet ventilation are now considered invasive airway techniques and are listed as such, along with a surgical or percutaneous airway. Retrograde intubation was removed from the list of suggested contents of the portable storage unit for difficult airway management.

Currently, there is heightened awareness of and an increase in the amount of literature being published on recognition and prediction of the difficult airway.  While some of the risk factors for each of these basic problems are unique, several risk factors overlap in multiple areas.  Newer methods of pre-operative airway evaluation include pre-operative endoscopic airway evaluation (PEAE) and ultrasonography, both of which could aid in identification of airway pathology, may assist in prediction of difficulty and ultimately help formulate a plan of anesthetic management.

Another significant change in the 2013 Difficult Airway Algorithm is that Videolaryngoscopy can and should be considered both as an initial approach to intubation (awake or following induction) and following failed intubation in which face mask ventilation is adequate.  Although not mentioned for use in the emergency pathway, it is the author’s opinion that video laryngoscopy could be considered if it had not been previously attempted, and the practitioner is experienced with this technique. The videolaryngoscope is now listed as one of the suggested devices in the portable storage unit for difficult airway management.

NEW AIRWAY TECHNIQUE/DEVICES

A common factor preventing successful tracheal intubation is the inability to visualize the vocal cords when performing direct laryngoscopy.  Although there are many new airway techniques and devices now available to the clinician, only a few will be highlighted here.  Selection of the device should be based on evidence, principles of accepted guidelines and proper judgment. Familiarity and confidence with the chosen device are key factors contributing to a successful outcome. Complex airway management, both in and out of the operating room setting, continues to be a challenge, and having the appropriate equipment and training can potentially reduce adverse events.

Flexible Fiberoptic Intubation has been and continues to be a very reliable approach to difficult airway management and airway assessment.  Technological advances, including improved optics, battery-powered light sources, better aspiration capabilities, increased angulation capabilities, and improved reprocessing procedures, have been developed.  Some of the newer systems include:  1) IntubaidFlexTM (EZC Medical, Inc., San Francisco, CA) which is a single-use video stylet for use during intubation, 2) Ambu aScope which is a completely disposable battery powered, flexible fiberoptic system and can be attached to a portable video monitor, 3) Flexible Digital Video Bronchoscope BRS-5000 (Vision  Sciences, Orangeburg, NY) is a reusable scope that uses disposable, sterile, endosheath®  technology with different channel size options 4) C-MAC 5.5 mm FIVE Scope is a new scope produced by Karl Storz which uses CMOS technology and is compatible with C-MAC monitor and C-HUB and 5) King Vision, a light weight and battery operated video laryngoscope with reusable video display and both channeled and non chaneled disposable blades.

There are a variety of supraglottic airway devices, which are now available to the practitioner.  Many of these devices have been adapted to allow intubation via the device, as well as evacuation of stomach contents.  The Ambu AuraOnceTM  (Ambu A/S) is a disposable, sterile laryngeal mask with a special built-in curve that replicates the natural human anatomy.  It is molded in one piece with an integrated inflation line and no epiglottic bars on the anterior surface of the cuff.33   It is available in both pediatric and adult sizes (1-5).  If intubation becomes necessary or desired, it is recommended to intubate over an Aintree Intubation Catheter (Cook Medical Critical Care, Bloomington, IN).  A new reusable version, the Ambu Aura40TM is also available.  It offers the same features and benefits as the disposable version.  A straight version of both types is manufactured in adult and pediatric sizes.  The Ambu Aura-iTM was recently introduced and designed as a conduit for endotracheal intubation featuring a novel connector block that prevents airway occlusions and ensues rotational stability.  It is available in 4 adult sizes (3-6) and 4 pediatric sizes (1-2,5).
The Air-Q Reusable Laryngeal MaskTM (formerly Intubating Laryngeal Airway [ILA]; Cookgas LLC, St Louis, MO; distributed by Mercury Medical, Clearwater, FL) is a reusable hypercurved intubating laryngeal airway that resists kinking and has a removable airway connect.  It is designed to minimize folding of the cuff tip on insertion.  A larger mask cavity allows intubation using standard ETs (sizes 5.5-8.5 mm).  ILA removal following intubation is accomplished using the removal stylet.  This laryngeal mask also comes in a new disposable version, the Air-Q Disposable Laryngeal MaskTM.    The Air Q BlockerTM combines the features of the Air-Q Disposable Mask with an additional soft flexible side tube located to the right of the ET which allows suctioning of stomach contents, insertion of a naso-gastric tube and facilitates venting.

In the last decade, a number of lighted stylets have been developed including lightwands, which rely on transillumination of the tissues of the anterior neck to demonstrate the location of the tip of the ET, as well as rigid fiberoptic stylets designed for indirect visualization of the airway.  The newest stylets are a hybrid of both rigid and flexible stylets and include the SensaScope® (Acutronic MS, Hirzel, Switzerland) and the RIFL Stylet™ (AI Medical Devices, Inc., Williamston, MI).

Video laryngoscopes are a relatively new addition to the armamentarium of 
devices for the airway manager and, as mentioned previously, are now included in the 2013 ASA Difficult Airway Guidelines. Video laryngoscopes offer a larger, brighter and higher resolution image, improve laryngoscopic grade and achieve the same or a higher intubation success rate often in less time, than direct laryngoscopes. Many are available in both adult and pediatric sizes with a trend in the direction of reusable handles with disposable blades for convenience.

Additionally, video assisted laryngoscopy allows the instructor to see what the trainee is visualizing in "real time" and allows for instruction and demonstration to multiple viewers. An assistant can visualize the effects of laryngeal manipulation, if needed, and the procedure can be recorded and reviewed later in presentations or discussions.  Video assisted laryngoscopy also can facilitate the teaching of alternative techniques, such as flexible fiberoptic endoscopy. Direct laryngoscopy can also be taught with certain video laryngoscopes, such as the Berci DCI, C-MAC and D-MAC (all KARL STORZ Endoscopy, El Segundo, CA), GlideScope® Direct (Verathon Medical, Botthell, WA) and McGrath MAC (Covidien, Mansfield, MA).

The Airtraq® Avant distributed by Airtrac LLC (Prodol Meditec-SA, Spain) is a disposable videolaryngoscope that includes a guiding channel to both hold and direct an endotracheal tube towards the vocal cords.  The Vividtrac (Mercury Medical, Clearwater, FL) is a new video assisted intubation device which sends its signal to any monitor with a USB port.  The use of video laryngoscopy may become routine, with its potential for important savings in time and decreased patient morbidity.

Specific airway techniques are greatly influenced by individual disease and anatomy, and successful management may require a combination of multiple approaches.  Thus, practitioners should gain knowledge of various combination strategies to increase their success in management of the difficult airway.  As with any intubation technique, practice and routine use will improve performance and may reduce the likelihood of complications.

AIRWAY EDUCATION

Additional airway devices continue to be introduced into clinical practice, thus continuing education and practice with these devices is essential for safe airway management.  As important as competence is in use of these devices is the ability to create and implement a variety of intubation plans. There are many new educational materials available to the clinician, including software programs, on-line instruction and books.

Some of the most recent books on airway management include Benumof and Hagberg’s Airway Management (3rd ed., ed: Hagberg), Management of the Difficult and Failed Airway (2nd ed., ed:  Hung and Murphy), Anesthesia for Otolaryngological Surgery (ed: Abdelmalak and Doyle) and The Difficult Airway – A Practical Guide (ed: Hagberg, Artime, and Daily).  These are excellent resources for clinicians which provide in-depth information, knowledge and practical guidelines on improving the success rates of airway management of all specialties who use modern airway devices and techniques.

There are many meetings which focus on airway management, including an upcoming international airway meeting, The World Airway Management Meeting (WAMM) which will be held November 12-14, 2015 in Dublin, Ireland.  This international conference will be jointly sponsored by the Society for Airway Management (SAM; United States of America) and the Difficult Airway Society (DAS; United Kingdom) to mark the 20th anniversary of both societies.  It will be held with the support of other airway management societies, including the European Airway Management Society.

EXTUBATION

Extubation, particularly of the difficult airway, is not without risk and should be taken seriously, as reflected in the last ASA closed claims analysis in which 12% of claims involving airway management are associated with this process.1  The practitioner needs to consider many factors, including the ease of the initial intubation, the patient’s medical status, the surgical procedure, the setting in which the extubation is going to occur, and finally, the practitioner’s skills and preferences.

Guidelines regarding extubation of the difficult airway were recently published by The Difficult Airway Society in the United Kingdom.4  These guidelines provide clinicians with pragmatic algorithms that apply to low-risk and at-risk-situations in which difficulty with oxygenation, ventilation and airway management may be expected.  Nonetheless, these Guidelines are mainly based on expert opinions, as there is a lack of any large randomized controlled trial of practices.  Cavallone and Vannucci5  found that a review of the current literature supports the adoption of a series of practices that are consistent with the ASA Practice Guidelines for Management of the Difficult Airway.

CONCLUSION

There is really not an optimum technology solution for management of the difficult airway.  Each device has unique properties that may be advantageous in certain situations, yet limiting in others. Nonetheless, clinical judgment born from experience is crucial to their application.  Any strategy chosen by the clinician should be well rehearsed in patients with non-problematic airways prior to implementation in those patients likely to be difficult.  A commitment to education and maintenance of skills is necessary for those who practice airway management.  Further investigation is necessary to evaluate outcomes of specific interventions and strategies which should ultimately lead to improvement in patient care.

1.Metzner J, Posner KL, Lam MS, Domino KB:  Closed claims’ analysis.  Best Pract Res Clin Anaesthesiol 25 (2):263-76, 2011.

2.Woodall NM, Cook TM:  National census of airway management techniques used for anaesthesia in the UK: first phase of the Fourth National Audit Project at the Royal College of Anaesthetists.  BR J Anaesth 106(2):266-71, 2011.

3.Previous update was developed by the American Society of Anesthesiologists Task Force on Difficult Airway Management:  Practice Guidelines for Management of the Difficult Airway: An updated report by the American Society of Anesthesiologists task force on management of the difficult airway.  Anesthesiology 118(2):251-70, 2013.

4.Difficult Airway Society Extubation Guidelines Group, Popat M, Mitchell V, Dravid R, Patel A, Swampillai C, Higgs A:  Difficult Airway Society Guidelines for the management of tracheal extubation.  Anaesthesia 67(3):381-40, 2012.

5.Cavallone LF, Vannucci A:  Review article: extubation of the difficult airway and extubation failure.  Anesth Analg 116(2):368-83, 2013.