1 History

Tobacco and alcohol use are associated with most cases of head and neck cancer and predispose these patients to chronic obstructive pulmonary disease, pneumonia, hypertension, coronary artery disease, and alcohol withdrawal. Information about previous surgical and anesthetic procedures with an emphasis on a history of anesthetic difficulties or difficult intubations, or both, must be obtained and communicated. Previous difficult airway management is considered to be one of the most important predictors of subsequent airway management difficulties.^2,3 Patients with a history of obstructive sleep apnea (OSA), especially those without an obvious anatomic abnormality, need careful assessment because their redundant pharyngeal mucosa and soft palate anatomy may hinder BMV and the ability to intubate. Common presenting symptoms of airway obstruction include dyspnea at rest or on exertion, voice changes, dysphagia, stridor, and cough. Physical findings may include hoarseness; agitation; and intercostal, suprasternal, and supraclavicular retraction. Voice changes provide an early suggestion of the anatomic level and severity and progression of the lesion. A muffled voice may indicate supraglottic disease, whereas glottic lesions often result in a coarse, scratchy voice. If there is suspicion of an anterior mediastinal, pharyngeal, or neck mass resulting in partial airway obstruction, initiating anesthesia in the patient in the supine position without first securing the airway may lead to complete airway obstruction and therefore deserves special preoperative evaluation.

2 Physical Examination

A systematic and comprehensive evaluation of the patient’s upper airway is mandatory. The condition of dentition, facial hair (beard), size and mobility of the tongue, thyromental distance, Mallampati score, and limitations in neck flexion and extension must be evaluated. A thyrocervical distance of less than 6 cm in a fully extended adult neck is a good indicator of difficult laryngoscopy and an inability to visualize the vocal cords. The presence and character of stridor should be appreciated, because it may suggest the location of airway narrowing (Table 39-1). Postirradiation changes, neck masses, and previous neck surgery may result in reduced neck mobility, causing difficult mask ventilation and difficult intubation. Findings of morbid obesity, evidence of any oropharyngeal or lip edema, and signs of upper aerodigestive tract bleeding may direct the preferred method of airway management. Lower cranial nerve dysfunction from tumor or previous surgery may also result in airway difficulty related to aspiration or obstruction.

TABLE 39-1 Evaluation of Stridor

a Endotracheal Intubation after Induction of General Anesthesia

In patients with no obvious or expected airway compromise, the ETT can be placed during direct laryngoscopy after induction with a short-acting paralyzing agent, such as succinylcholine. Because it is difficult or impossible to empty the stomach with a nasogastric tube in the case of a large pharyngeal or esophageal tumor, the patient is assumed to have a full stomach.⁶ Risk of aspiration is reduced by preinduction administration of ranitidine, metoclopramide, and oral sodium citrate–citric acid buffer (Bicitra, Willen Drug Co., Baltimore, MD). The Hollinger anterior commissure laryngoscope is a valuable tool in difficult airway management, and it should be considered when other techniques have failed. This scope may accommodate a 5.0-mm or smaller cuffed ETT, but the insufflation port may become lodged in the barrel of the scope. To avoid this issue, a trial passage of the ETT through the laryngoscope should be attempted before the performance of direct laryngoscopy.⁷

b Nasotracheal Intubation in the Awake Patient

If a difficult airway or difficult intubation is anticipated from the preoperative examination or awake assessment of the airway has mandated an awake intubation, nasotracheal or orotracheal intubation of an awake patient may be performed. The choice of route is directed by the surgical requirement and by the physical condition of the patient. Continuous administration of supplemental oxygen (O₂) during the entire process is mandatory.

The nasotracheal route is useful in cases of small mouth opening, severe trismus, large tongue, receding lower jaw, large oral cavity tumor, planned maxillomandibular fixation, or tracheal dilatation. Operator and equipment positioning relative to the patient is depicted in Figure 39-1. For nasal intubation, the nose is prepared with a nasal decongestant spray, such as pseudoephedrine (Afrin) and topical 4% cocaine. Cocaine is more advantageous than lidocaine because it is a vasoconstrictor in addition to being a very effective surface anesthetic. The potential for abuse by the personnel is occasionally a deterrent for its routine use. In placing the ETT through the nose, it is necessary to remember that the nasal floor usually runs in a horizontal plane perpendicular to an imaginary vertical line connecting the glabella and the pogonion. The ETT is advanced to approximately the 15-cm mark, and the connector is removed. The flexible fiberoptic bronchoscope (FFB) is then used to visualize the glottic opening and to introduce the tube into the trachea.

Figure 39-1 The optimal setup for fiberoptic intubation includes elevation of the patient’s head to minimize airway collapse. The intubator should be facing the patient, allowing the entire team to observe the procedure on the video monitor.

(From Bhatti NI: Surgical management of the difficult adult airway. In Flint PW, editor: Cummings otolaryngology-head and neck surgery, ed 5, Philadelphia, 2010, Elsevier, pp 121–129.)

c Fiberoptic-Guided Orotracheal Intubation

Orotracheal intubation is facilitated with an oropharyngeal airway (OPA), such as a Williams or Ovassapian OPA. Similar to nasotracheal intubation, optimal topical anesthesia of the oral cavity and oropharynx is warranted to overcome the patient’s gag reflex. The lubricated ETT, with its connector removed, is loaded onto the proximal end of the FFB. The tip of the scope is then introduced through the OPA and passed behind the epiglottis into the glottic opening leading into the trachea. When the scope is past the vocal folds, the tracheal rings should be identified before advancing the ETT. The ETT is then eased into the trachea over the scope, and placement is confirmed with a combination of bilateral chest auscultation and end-tidal carbon dioxide (EtCO₂) measurement. After confirmation of the placement, general anesthesia is induced.

d Rigid Bronchoscopy

The rigid bronchoscope, a hollow stainless steel tube through which a rigid telescope is placed, provides excellent access to the airways. The distal end of the rigid bronchoscope is usually beveled to facilitate intubation and lifting of the epiglottis. The updated American Society of Anesthesiologists (ASA) protocol states that in the “cannot intubate, cannot ventilate” (CICV) scenario, “a rigid bronchoscope for difficult airway management reduces airway-related adverse outcomes.”⁸ This modality is recommended as a technique for cases of difficult mask ventilation. Other indications for rigid bronchoscopy include massive airway hemoptysis, foreign body retrieval, laser or photodynamic therapy, and placement of airway stents.⁹

e Retrograde Intubation

Though rarely used, retrograde intubation represents another alternative technique for intubation of the difficult airway in head and neck patients. This technique can also be used in patients with trismus, trauma to the cervical spine, temporomandibular joint ankylosis, upper airway masses, or failed intubation. This technique begins with puncture of the cricothyroid membrane (CTM) or cricotracheal membrane with a small needle angled superiorly to pass a guidewire through the larynx, and it is then guided through the nose or mouth. The ETT is then advanced over the guidewire with a Seldinger technique into position in the trachea.¹⁰

Retrograde intubation may also be used to facilitate other approaches. For example, a combination of conventional, fiberoptic, and retrograde techniques can be used to intubate successfully.¹¹ An FFB with a suction port can be used as an anterograde guide over a retrograde wire. A direct laryngoscopic view can facilitate placement of the tip of a fiberoptic scope into or near the glottic aperture. After the FFB is past the vocal folds and tracheal rings have been identified, the preloaded ETT may be passed over the FFB into the trachea.

f Tracheostomy with Local Anesthesia

If a patient is in acute respiratory distress because of upper airway obstruction and the patient is considered unable to be safely intubated under general anesthesia after evaluation (including FFB), the best choice is to perform a planned but urgent awake tracheostomy.¹² This should be performed under local anesthesia with minimal intravenous sedation to avoid loss of spontaneous breathing. Tracheostomy under local anesthesia in an awake patient is also an excellent method to secure the airway in the following situations: upper airway abscess that may be in the way of or distorting the pathway for endotracheal intubation; bulky, friable supraglottic or glottic mass; and glottic stenosis with presumed bilateral cricoarytenoid joint fixation. In these situations, attempts at direct laryngoscopy and intubation may result in abscess rupture or aspiration of purulent material, blood, or material from a friable tumor, or in the case of cricoarytenoid joint fixation, the fixed, medialized vocal folds do not allow passage of the ETT without severe damage to the membranous vocal folds.