Surgical Management of the Difficult Adult Airway

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CHAPTER 10 Surgical Management of the Difficult Adult Airway

Failure to maintain a patent airway may result in catastrophic events for the patient, including brain damage or death. In 1990, more than 85% of all respiratory event–related closed malpractice claims involved an anoxic brain injury or death.1 Difficulties with intubation and emergent airway issues remain the leading causes of serious intraoperative complications.2 As many as 30% of deaths attributable to anesthesia involve failure to manage the difficult airway.3 In any given patient, the risk of anoxic injury or death increases in direct proportion to the degree of difficulty in maintaining a patent airway.4 Any scientific or clinical description of the difficult airway must include clearly defined terminology. In this chapter, the difficult airway must be considered as involving three distinct but often clinically related scenarios.

The first of these is difficult tracheal intubation. This condition exists when multiple attempts are needed in the presence or absence of tracheal disease. An infinitely difficult intubation means the trachea cannot be intubated under direct vision, despite full paralysis, optimal head and neck positioning, cricoid pressure, forceful anterior elevation of the laryngoscope blade, and attempts by multiple operators with a variety of laryngoscope blades.4 The incidence of failed endotracheal intubation ranges from 5 to 35 in 10,000 patients.5,6

The second difficult airway scenario is the difficult laryngoscopy. Difficult laryngoscopy is described as not being able to visualize any portion of the larynx, vocal folds, or glottic aperture after multiple attempts at conventional laryngoscopy. Many investigators include grades III and IV or grade IV alone, according to the Cormack-Lehane original grading of the rigid laryngoscopic view.7 For studies of difficult laryngoscopy to be reliable and for the preceding laryngoscopic grading system to be helpful, the reported grades must describe the best view that was obtained, which in turn depends on the best performance of laryngoscopy.4 The technical components that optimize laryngoscopy include optimal position, complete muscle relaxation, firm forward and upward traction on the laryngoscope, and, if necessary, firm external laryngeal manipulation with cricoid pressure. External laryngeal pressure, for example, may reduce the incidence of grade III view from 9% to 1.3%.8 Theoretically, if the preceding technical components of laryngoscopy are used and the pitfalls avoided, all laryngoscopists (novice and expert) should have close to the same laryngoscopic view. Difficult laryngoscopy is synonymous with difficult intubation in most patients. A grade II or III laryngoscopic view requiring multiple attempts with different blades, or both, is relatively common, occurring in 100 to 1800 of 10,000 patients.9 The incidence of a higher grade III laryngoscopic view ranges from 100 to 400 of 10,000 patients.10,11

The third difficult airway scenario is difficult mask ventilation (DMV), which is a condition in which it is not possible to provide adequate face mask ventilation as a result of inadequate mask seal, or excessive resistance due to inadequate patency of airway.4 Langeron and colleagues compiled a list of predictors of difficult mask ventilation based on a survey of anesthesiologists asking them to rate difficulty of face mask ventilation.12 This difficulty was based on whether it was clinically relevant and could have led to potential problems if mask ventilation had to be maintained for a longer time. Six reasons for DMV were identified: (1) inability of the unassisted anesthesiologist to maintain oxygen saturation to greater than 92% using 100% oxygen and positive-pressure mask ventilation, (2) significant gas flow leak by the face mask, (3) necessity to increase the gas flow to greater than 15 L/min and to use the oxygen flush valve more than twice, (4) no perceptible gas movement, (5) necessity to perform a two-handed mask-ventilation technique, and (6) change of operator required.

The incidence of DMV is difficult to estimate in that there has not been a standard definition used universally by researchers, so each study needs to be carefully read to determine the definition used. Langeron and colleagues reported a 5% incidence of DMV with 1 in 1502 patients being impossible to ventilate with a face mask.13 A very significant finding from this study is that DMV conferred a fourfold increased risk for difficult intubation and 12-fold increase in the risk for an impossible intubation.

The incidence of the ultimately critical failed airway, the “can’t intubate, can’t ventilate” situation, can be estimated because it frequently results in anoxic brain injury or death, ranging from 0.01 to 2 of 10,000 patients.14,15 Although the cause of this dire apneic or obstructive state may be completely or partially related to the patient’s disease, there is often an identifiable iatrogenic component. The clinicians caring for the patient in this urgently life-threatening state must be prepared to act swiftly and decisively in order to sustain or recover oxygen saturation and ensure ventilation.

With these definitions in mind, it is important to realize that identification of the difficult airway before manipulation is crucial, and the key step in preparing for optimal patient care and a safe outcome.16 Selection of airway equipment or devices, techniques, and procedures all pivot on airway evaluation. The literature provides strong evidence that specific strategies and communication of these strategies with the airway team facilitate management of the difficult airway. The American Society of Anesthesiologists’ (ASA) algorithm on the management of the difficult airway is an example of such collaborative effort and should act as a foundation for locally developed institution-specific action strategies.17 Refer to the differences between 1993 and 2003 versions of the ASA algorithm (Box 10-1).

When considering management options for the difficult airway situation, the anesthesiologist and surgeon must give consideration to aborting the planned procedure, waking the patient, and reassessing airway management options before proceeding. When this is not an option, the team must consider alternative techniques for laryngoscopy such as the video-assisted Glidoscope, placement of a laryngeal mask airway (LMA) and intubation by fiberoptic laryngoscopy with or without an Aintree catheter, or direct laryngoscopy with an anterior commissure (Hollinger) laryngoscope and intubation through the laryngoscope.

Use of the LMA in the difficult airway situation has increased as equipment has evolved to facilitate intubation through the LMA. The success of this device led to the introduction of the intubating LMA (LMA Fastrach) into clinical practice.18,19 Intubation may be accomplished by passing the endotracheal tube (ETT) alone through the LMA (blind technique), or by intubation over a fiberoptic bronchoscope with or without an Aintree catheter placed over the bronchoscope. This technique provides visualization of the intubation and may be combined with videoendoscopy. The addition of the Aintree catheter facilitates intubation after removal of the LMA if this is required to proceed with surgery.

The Hollinger anterior commissure laryngoscope is the otolaryngologist’s most useful tool in difficult airway management, and should be considered when all other techniques have failed. This is particularly true for fixed laryngeal and subglottic lesions where a small cuffless ETT may be passed under direct visualization. The Hollinger scope will accommodate a 5.0 or smaller cuffed ETT, although the insufflation port may become lodged in the barrel of the scope. This should be determined before intubation. An Eschmann stylette may also be passed through the laryngoscope and the ETT passed over the stylette, allowing placement of a larger sized ETT (Figs. 10-1).

Awake fiberoptic intubation should always be considered as a viable option, especially in the anticipated difficult airway situation. This technique is discussed in more detail in following sections.

Surgical procedures such as open cricothyroidotomy, tracheostomy, and transtracheal jet ventilation must be considered when faced with the “can’t intubate, can’t ventilate” situation. The role an otolaryngologist can play in such situations is critical, providing expertise in endoscopic techniques with the ability to provide open surgical access to the airway. The indications, contraindications, technique, and strategies to optimize success with these techniques are discussed herein in detail.

Awake Fiberoptic Nasotracheal Intubation

Awake fiberoptic nasotracheal intubation is now a common technique employed in the management of the difficult airway in both the operating room and intensive care unit settings.

Historical Perspective

Flexible fiberoptic technology has provided the vehicle for developing and perfecting these intubation techniques. A flexible fiberoptic choledochoscope was first used for nasotracheal intubation on a patient with Stills’ disease as early as 1967.29 Five years later, nasotracheal intubation was successfully carried out in a patient with severe rheumatoid arthritis using a fiberoptic bronchoscope (FOB).30 Stiles and colleagues subsequently reported the first series of 100 fiberoptic endotracheal intubations.31 These intubations were performed both orally and nasally, and the authors suggested that with experience, fiberoptic intubation could be performed in less than 1 minute.

Davis and colleagues described the use of FOB for checking the ETT position in relation to carina.32 Use of FOB in assessing ETT position was shown to be as good as chest radiography in both adults and children.33,34 Many other uses of FOB technique were also described, especially in critically ill patients, to evaluate the upper and lower airway.3538 Several authors cited advantages of the technique, including the ability to perform diagnostic and therapeutic procedures at the bedside without general anesthesia and without interruption of ongoing mechanical ventilation. Another advantage cited was the ability to perform the procedure orally, nasally, or through an in situ ETT or tracheostomy tube. One main disadvantage reported by many authors was the increased airway resistance particularly in pediatric patients because the FOB may occupy a significant portion of the lumen of the tube. FOB was not originally developed for the management of the difficult intubation.39 However, as technology was advanced and visualization improved, anesthesiologists soon appreciated the value of the FOB in the management of the difficult airway.4043 Use of the FOB has been described for airway management in Ludwig’s angina,44 rheumatoid arthritis,45 trauma,46 unstable cervical spine,47 disruptive injuries of the soft tissue of the neck,48 acromegaly,49 and Pierre Robin syndrome,50 among other conditions. Several authors have reported successful use of the FOB in securing the airway in awake patients with increased risk of aspiration.5154 As a result, the teaching of fiberoptic airway endoscopy is now an integral part of training for otolaryngology head and neck surgery (OHNS), anesthesiology, and emergency medicine.

Indications

When the airway is compromised or a difficult airway is anticipated, awake fiberoptic intubation (FOI) with or without sedation should be considered (Box 10-2). Awake fiberoptic intubation is an ideal procedure for patients with morbid obesity, supraglottic mass, or edema with the ability to visualize the glottic aperture, risk of aspiration, history of known DMV, patients with limited mandible excursion or trismus, and history of prior difficulty with transoral intubation using other techniques. Contraindications to awake fiberoptic intubation include fixed stenotic lesions at all levels that will not allow passage of an ETT without dilatation, active bleeding obscuring visualization, and acute obstructing supraglottitis, as well as in patients unable to cooperate during the examination. In general, many patients who might be denied general anesthesia or receive a tracheostomy can be safely intubated using the FOB. To intubate patients safely and quickly, certain preparatory steps should be taken.

Bronchoscopy Cart

Proper functioning equipment is essential to a successful outcome. A fully equipped videobronchoscopy cart should be available for use in the intensive care units, emergency department, critical care wards (e.g., otolaryngology patient floor) as well as in the operating room. All equipment and supplies for administration of anesthesia, resuscitation, and monitoring should be available and should be checked following a standard protocol before beginning a nonemergent fiberoptic intubation (Fig. 10-2). For awake intubations, the cart is placed on the left side at the head of the bed while a right-handed operator stands on the right side facing the patient. The light source should be checked for integrity and the necessary supplies are laid out on top of the fiberoptic cart, and suction is connected and at hand. The cart should contain ancillary equipment including nasopharyngeal airway and endotracheal tubes (standard and MLT long tubes), among other items.

Fiberoptic Intubation of the Conscious Patient

The advantages of awake fiberoptic intubation include maintenance of spontaneous ventilation and the ability to position the tip of the ETT precisely beyond the obstruction/compression. It is easiest in the awake near upright patient because the tongue does not fall back in the pharynx, and breathing tends to keep the airway open. In addition, with deep inspiration, the patient can assist the operator in locating the glottis when airway anatomy is distorted. Box 10-3 lists the factors that are crucial for successful completion of an awake fiberoptic intubation. These include training and preparation of the airway team, psychological and pharmacologic preparation of the patient, appropriate monitoring and delivery of oxygen during preparation of the patient and the procedure, expertise of the operator, and a well-functioning bronchoscopy cart.