The gag reflex is much less reliable than phonation and swallowing, and it is absent in up to 25% of the normal adult population.³ The presence of a gag reflex does not equate to airway protection, nor does its absence indicate a need to intubate. The presence or absence of the gag reflex is better thought of as a neurologic evaluation (i.e., cranial nerves IX and X) rather than as part of an airway evaluation. The Glasgow Coma Scale is a better tool for predicting intubation.⁴

The ability of a patient to maintain appropriate oxygenation and ventilation can be assessed clinically and supported by pulse oximetry and capnography. Although arterial blood gas values are useful in evaluating the trauma patient with respect to identification of occult acidosis that may represent more severe shock than is clinically apparent, these determinations have little or no role in the decision to intubate. Evaluation of the patient’s respiratory effort and the overall sense of the patient’s injuries in the context of pulse oximetry readings are more important to the intubation decision than arterial blood gas values. Patients with compromised ventilation or oxygenation should receive high-flow face mask oxygen (O₂) with a reservoir, and all reversible issues should be addressed. Hemothorax, pneumothorax, flail chest, and opioid overdose are examples of reversible conditions that compromise oxygenation and ventilation. Most cases of hypoxemia or hypoventilation in multitrauma patients are multifactorial and do not respond to simple interventions. In these cases, early intubation usually is indicated.

Most trauma patients can maintain and protect their airways and exhibit adequate or correctable oxygenation and ventilation. For them, it is the anticipated clinical course that guides the decision to intubate. This is the most sophisticated and most important of the decisions facing the airway manager or trauma captain. A patient may appear stable at the time of evaluation, but deterioration can be predicted as a natural course of the injuries. For example, the patient with burns from a closed-space fire with significant inhalation of superheated air (see Chapter 44) may present with a somewhat hoarse voice or a simple cough but has an otherwise patent airway. Failing to recognize the likelihood of progressive obstruction of the airway, which has been subjected to toxic and thermal insults, and to intervene in a timely fashion can lead to disaster. Although the patient may not meet the criteria for emergency intubation related to airway maintenance and protection, oxygenation, or ventilation, the likelihood of deterioration is alone sufficient to warrant airway intervention.⁵ It is the predictability of the deterioration that determines the decision to intubate. Alternatively, the upper airway can be examined by fiberoptic laryngoscopy, informing the airway manager of the stability or fragility of airway patency. Similarly, the patient with a crushed pelvis, open femur fracture, and hypotension is inevitably intubated, even though there is no immediate threat to airway patency or oxygenation. The need for advanced imaging, aggressive pain control, and operative repair of obvious injuries dictates that the patient be intubated early and in a more controlled fashion than trying to manage a chaotic intubation from behind the computed tomography (CT) scanner.

Consideration of the patient as a whole, of the individual injuries and how they interact, of the effects of these injuries on the patient and on the patient’s comorbidities, and of the need for interventions (including transport) frequently guides a prudent and rational decision to intubate, even when the patient does not have an immediate airway problem and when oxygenation and ventilation are adequate.

Preventing morbidity or mortality as it relates to trauma airway management refers to delaying intubation rather than to a mishap occurring during intubation. It is better to err on the side of intubating early and securing a potentially threatened airway than observing the patient with a false sense of security born from adequate oxygenation and ventilation at that moment. The purpose of observation is to see whether obstruction or airway failure ensues, but if either occurs, the results may be disastrous.

II Anatomy of the Airway: Trauma Considerations

Although airway anatomy is discussed in Chapter 1, the following is a brief description of elements to consider in the trauma setting. The airway begins at the nares or lips and ends with the terminal bronchioles and alveoli of the lungs. The upper airway consists of the oral and nasal cavities and the pharynx, which provide a conduit for the movement of gases to the larynx, through the glottis, and into the trachea. The nasopharynx, oropharynx, and hypopharynx (Fig. 41-1) form a continuous space that conducts air from the outside world to the glottic aperture. The nasopharynx is protected anteriorly and laterally by the maxillary bones, the nasal bones, and nasal cartilage. Direct injury to the face, particularly from an impact with an object of high mass, high velocity, and low surface area (e.g., baseball bat), can collapse the maxillary structures into the nasopharynx and cause extensive hemorrhage, threatening the airway and complicating attempts to manage it. Similarly, the oropharynx is protected by the maxillary bones, alveolar ridges, and mandible but is subject to the same sort of intrusive injuries. Blows to the face producing Le Fort I, II, or III fractures (Fig. 41-2) can simultaneously threaten the airway and complicate airway management.

Figure 41-1 Airway anatomy.

(From Redden RJ: Anatomic considerations in anesthesia. In Hagberg CA, editor: Handbook of difficult airway management, Philadelphia, 2000, Churchill Livingstone, p 11.)

Figure 41-2 Le Fort classification.

The larynx and trachea are essentially subcutaneous structures in the anterior neck. The larynx is separated from the skin only by subcutaneous fat and the anterior cervical fascia. The thyroid notch, cricothyroid membrane, and cricoid cartilage can be easily palpated to provide the critical landmarks for surgical access to the airway (see Chapter 31). The airway is mobile in the neck but is fairly firmly anchored by the strap muscles and cervical fascia. Tracheal deviation as a result of pneumothorax or hemothorax may occur in patients who are severely compromised.⁶ Tracheal deviation is not helpful as a sign of pneumothorax because it usually occurs only when the pneumothorax is at an advanced state and easily identifiable by auscultation. Tracheal deviation can result from disruption of the neck anatomy caused by hemorrhage or extensive subcutaneous emphysema. It is also seen with chronic scarring, such as that related to previous radiotherapy. In any case, palpation of the trachea and larynx is a valuable exercise in the event that surgical airway management becomes necessary. It also can establish the position of the airway in the neck, even if orotracheal intubation is contemplated. Orotracheal intubation can be extraordinarily difficult or impossible when the trachea or larynx is displaced laterally.

Vascular structures in the neck, such as the carotid artery and jugular vein, do not have a direct bearing on the airway. Nonetheless, they can be the cause of significant airway compromise when vascular injury from blunt or penetrating trauma creates hemorrhage that displaces or otherwise changes the configuration of the airway. The nerves supplying sensation to the supraglottic larynx and the remainder of the airway are rarely injured by trauma.

Knowledge of the anatomy of the upper airway is no more or less important in the management of the multitrauma patient than in any other setting in which emergency airway management is required. When specific trauma to the maxillofacial area or neck threatens and disrupts the airway, however, anatomic knowledge and the ability to improvise an approach may be key determinants of success.

III Specific Clinical Considerations in Trauma

A Direct Airway Trauma

Direct trauma to the airway can be broadly classified as blunt or penetrating trauma. Each of these categories can be considered in the context of direct injury to the airway itself versus compromise or threat to the airway caused by the proximity of an injury in the neck. Injury to the airway can occur at one or more levels. Maxillofacial trauma can compromise the upper airway; direct injury to the neck can compromise the airway from the hypopharynx to the trachea; and injuries to the thorax can disrupt the lower trachea, main stem bronchi, or other smaller bronchi. The approach to airway management is dictated by the clinical presentation of the patient and the best judgment of the operator.

1 Penetrating Neck Trauma

Penetrating neck injuries range in scope from stab or other puncture wounds to major lacerations due to both low-velocity (e.g., BBs, pellets) and high-velocity (e.g., crossbows, firearms) projectile injury. The consequences of these various mechanisms can vary drastically. The overall mortality rate due to penetrating neck injuries is 2% to 6%, with a significantly lower mortality rate for low-velocity injuries.⁷^–⁹ The patient with a stab wound to the neck usually has identifiable anatomy and can undergo a planned airway evaluation and early intubation under controlled circumstances. Patients with high-velocity injuries often have significant vascular and hollow-structure injuries, and anatomic distortion can make airway management challenging.¹⁰ These injuries mandate urgent airway management, but the approach is confounded by the myriad injuries caused by the missile.¹¹

For the purposes of classification of penetrating injury, the neck is divided into three zones (Fig. 41-3). Zone 1 extends from the clavicles inferiorly to the level of the cricoid cartilage. Zone 2 extends from the cricoid cartilage to a line drawn through the angles of the mandible, and zone 3 is the area above the angles of the mandible. This classification is most useful for low-velocity penetration, such as from a stab or long-distance birdshot, but it has also been applied to high-velocity injuries, such as rifle wounds.¹⁰ These zones were designated because of their unique anatomic characteristics.¹² Zone 1 is dominated by the major vascular structures at the root of the neck, specifically the carotid arteries, internal jugular veins, subclavian arteries and veins, and innominate arteries and veins. The airway at this level is relatively inaccessible except by tracheotomy. Zone 1 injuries are relatively uncommon (<10% of penetrating neck injuries) but are often associated with major vascular injuries or injuries to the dome of the lung.¹³ Patients with zone 1 injuries often require emergency airway management because of direct airway compromise by hemorrhage or the anticipated clinical course predicted by the profound shock that typically develops. There is little literature to guide the selection of airway management techniques for zone 1 penetrating injuries. Most information is limited to small case series of subsets of larger series that are dominated by zone 2 injuries. The approach to airway management is dictated more by the nature of the threat to the airway than by the location of the inciting wound. The overall approach to airway management in penetrating neck injuries is outlined subsequently.

Figure 41-3 Zones of the neck.

Zone 2 is the most common location for penetrating neck injuries, accounting for most reported cases.¹⁴ Zone 2 injuries require emergency airway intervention in approximately one third of the cases, with a large proportion of the remainder undergoing subsequent intubation related to evaluation or surgical repair. The area of concern in zone 2 extends from the anterior margins of the paravertebral muscles bilaterally. In this area, major vascular structures (e.g., common carotid arteries, internal jugular veins) and their associated sympathetic ganglia and the hypopharynx, esophagus, larynx, and trachea are all at risk. The most common cause of airway compromise in zone 2 injuries is external distortion by hemorrhage related to vascular injuries or direct injuries to the airway.¹⁵

Zone 3 injuries are uncommon (<10% of all penetrating neck injuries) because of the very small area involved and the protection provided by the mastoid processes posteriorly, the mandible anteriorly, and the base of the skull superiorly. The area, however, is rich with major vascular structures (i.e., carotid arteries and internal jugular veins) and provides easy access to the pharynx. Surgical repair of injuries in this area is difficult, and most of these patients undergo extensive evaluation by angiography, with stenting of vascular injuries often the intervention of choice. Because zone 3 injuries involve the pharynx, direct airway compromise is uncommon except by hemorrhage into the airway from a through-and-through injury to the carotid artery. In these rare circumstances, immediate airway intervention is required and may be difficult because of the torrential hemorrhage. Orotracheal intubation is usually successful in these cases, however, particularly if the patient is positioned head down to prevent the blood from entering the operator’s view. After the airway is secure, the mouth can be packed tightly with gauze to control the internal hemorrhage while direct external pressure is simultaneously applied as the patient is transported to the OR.

The approach to the airway in the patient with penetrating neck trauma is guided by the same principles that were outlined earlier in this chapter. Compromised airway patency or protection because of hemorrhage, for example, is an indication for active airway management. Similarly, severe shock with overall obtundation of the patient and an inability to protect the airway or ventilate and oxygenate adequately makes the intubation decision fairly straightforward. The difficulty lies in the patient who has evidence of injury to the neck, but who does not have an obviously compromised airway at the initial evaluation. It is in these cases that judgment is most important and that most tactical errors are made.

The best approach is to consider two specific issues. The first is whether there is evidence of a direct injury to an air-containing structure in the neck. Subcutaneous air indicates injury to an air-filled structure in the neck,¹⁶ such as the airway (including the hypopharynx or pharynx) or the esophagus. In severe cases, particularly patients with injury to both vascular and air-filled structures, airway obstruction can occur rapidly, requiring emergency cricothyrotomy.¹⁷ In less threatening cases, it is virtually impossible to tell whether the esophagus or airway is involved, and early direct or fiberoptic examination of the airway is indicated. Sedation and topical anesthesia allows the operator to determine the severity and location of any airway injury. Preparation with a small to moderate-size endotracheal tube (ETT) (e.g., 6.0- to 7.0-mm inside diameter) mounted on the scope before initiating endoscopy facilitates prompt intubation if the injury is found to be significant. If the scope has been placed successfully distal to the injury, the patient can be gently intubated over the flexible fiberoptic bronchoscope (FFB), because it is best to secure the airway distal to the injury. This at least ensures that the patient is safe until he or she can be transported to the OR for further evaluation by an otolaryngologist or general surgeon. Although tracheostomy is often necessary, in these cases, temporary oral endotracheal intubation over an FFB ensures airway control and minimizes the subsequent leakage of air into the tissues, facilitating later repair.¹⁶ If no airway injury is identified and there is no evidence of increase in the subcutaneous emphysema in the neck during spontaneous or assisted ventilation, the injury can be presumed to be esophageal.¹⁸ If, however, circumstances change and subcutaneous emphysema begins to increase, even slightly, intubation is recommended since development of large amounts of subcutaneous emphysema can distort airway anatomy such that subsequent intubation or surgical airway management becomes difficult or impossible. As with all penetrating neck injuries, early intubation, even in patients who do not appear to immediately require it, is the most prudent course.

The second issue is whether there is evidence of significant vascular injury to the neck. All penetrating neck wounds have some external bleeding, although it can be surprisingly modest. The issue with respect to airway management is whether injury has occurred to any of the major vascular structures in the neck (e.g., carotid arteries, jugular veins). A hematoma of any size, external hemorrhage, or any evidence of displacement of the airway structures can serve as evidence of direct vascular injury. As soon as it has been established that direct vascular injury has occurred, active airway management should be undertaken.^19,²⁰ Most of these patients present early in the course of their injuries, when anatomy is preserved and orotracheal intubation is likely to be relatively easy to achieve. Waiting to determine whether the hematoma is expanding is perilous, because most of the hemorrhage into the neck occurs into the deep tissue planes, distorting and displacing the airway without external evidence until a crisis occurs. The time-honored dictum that hematomas of the neck should be observed to see whether they are expanding is not rational, and any evidence of direct vascular injury to the neck is sufficient justification for intubation. Early intubation can proceed using a rapid-sequence intubation (RSI) technique if a careful examination for difficult airway attributes fails to identify problems and there is a sound rescue strategy planned in the event of intubation failure.²¹ Early intervention allows the operator to intubate in a controlled fashion rather than scrambling to secure an emergency airway later in the patient’s course, when airway obstruction is imminent or has already occurred.

If there is doubt regarding oral access, three approaches can be considered. The first option is to perform oral RSI under a double setup with preparations and personnel in place to perform immediate surgical cricothyrotomy if orotracheal intubation is not successful. This approach should only be undertaken only if the preintubation airway assessment indicates that orotracheal intubation, although potentially difficult, is still likely to be successful. Similarly, there must be confidence that bag-mask ventilation (BMV) will be successful in maintaining the patient’s oxygenation, if required. If visualization is suboptimal during conventional direct laryngoscopy, the use of a bougie or video laryngoscope can be considered.

The second option is to perform fiberoptic intubation under sedation and topical anesthesia, as described earlier. This allows the operator to use the FFB to identify and enter the airway, even if the anatomy has become distorted. If this is undertaken early in the patient’s course, there is typically sufficient time and control to yield a high success rate. However, a distorted and bloodied airway makes fiberoptic intubation technically challenging, and the most experienced operator should perform the procedure.

The third option is to proceed directly with a planned surgical cricothyrotomy. This requires that the airway be identifiable with clear landmarks to permit a surgical approach. Local anesthetic infiltration and direct transcricothyroid puncture for instillation of local anesthesia into the airway are likely to make the procedure easier to perform (see Chapter 31).

In all cases of penetrating neck trauma, early consultation with an otolaryngologist or general surgeon is essential. Initially innocuous injuries may lead to catastrophic consequences for the patient if not identified and managed early.²² Early airway intervention permits controlled resuscitation and prevents major morbidities related to penetrating neck injury, such as airway compromise with resultant hypoxia or anoxia.

2 Blunt Neck Trauma

Many of the management issues related to penetrating neck trauma apply in an analogous fashion to management of the patient with blunt neck trauma. The primary difference is related to the inability to precisely localize the injury (i.e., no obvious skin penetration to identify the point of injury) and the fact that blunt injury is usually more diffuse. Initial evaluation of the patient with a blunt neck trauma should include identification of bruising or ecchymosis related to the external injury. The oropharynx should be inspected to ensure that there is no injury to the tongue or dentition. The external neck should then be palpated carefully from the mandible to the clavicle. Palpation is focused on three findings:

1. Identification of swelling, hemorrhage, or subcutaneous emphysema

2. Evaluation for tenderness (if possible) of the neck, particularly the airway structures

3. Evaluation of the anatomy of the upper airway for direct airway injury and for the anatomic landmarks that are important if a surgical airway must be placed (see Chapter 31).

Because subcutaneous emphysema may be occult, it requires careful palpation. Extensive ecchymosis suggests blunt vascular injury with free hemorrhage (which is usually venous) or formation of a pseudoaneurysm. Extensive ecchymosis or extensive swelling strongly suggests impending airway compromise, and urgent airway intervention is advisable.²³ Infrequently, direct blunt neck trauma can cause laryngeal fracture or tracheal transsection. The latter is often rapidly fatal, but patients may arrive in the trauma resuscitation area alive because of incomplete transsection.²⁴ In these cases, there is usually subcutaneous air, often accompanied by swelling, and pain elicited by palpation of the anterior airway. Although a trial of BMV may be tempting, it is likely to exacerbate the subcutaneous emphysema and accelerate the patient’s deterioration. When such an injury is identified, the best approach is prompt transfer to the OR for surgical exploration of the anterior neck and establishment of the airway by tracheostomy distal to the transsection. Often, however, airway management must be undertaken before the surgery, and careful awake fiberoptic intubation over a small FFB after inhalational induction may be the least of all evils. If the airway must be secured in the ED, for example, before transportation to a level I trauma center, the same approach is used, substituting intravenous sedation and topical anesthesia for inhalational anesthesia because the latter is not available in the ED.

As with penetrating neck injuries, the key error in the management of the patient with blunt neck trauma is observing an already distorted airway to determine if the condition worsens. If the patient exhibits evidence of significant neck injury, it can be assumed that the airway is threatened. When this threat advances to actual airway compromise, it threatens the patient’s life and thwarts subsequent attempts at airway management. As with penetrating trauma, early airway management is indicated when there is evidence of significant blunt injury to the neck.

Airway management is complicated by the fact that patients with blunt anterior neck trauma must be presumed to have a C-spine injury. Up to 50% of patients with blunt airway injury have a C-spine injury,²⁵ which is discussed here in the context of airway management.

In clothesline injuries, in which the neck is struck, usually transversely, by a fence wire or similar object, the central neck area may be significantly but deceptively disrupted from the impact.¹⁷ Although these injuries can be dramatic and often require immediate airway management, the airway itself is often intact, signified by identification of intact structures and the absence of air bubbling or gurgling during negative-pressure or positive-pressure ventilation. Early intubation from above, preferably over an FFB, is best in these cases. If the airway has been breached, and gurgling or subcutaneous air is evident in the tissues of the neck, positive-pressure BMV is not likely to be successful in oxygenating the patient, and attempts at BMV may result in insufflation of large amounts of air into the soft tissues of the neck, further compromising the airway and the attempts at securing it. The best approach in these cases is to attempt to secure the airway over an FFB using sedation and topical anesthesia, with a plan to progress directly to a cricothyrotomy or emergency tracheostomy, if fiberoptic intubation is unsuccessful.

3 Maxillofacial Trauma

Mandibular fractures are usually isolated injuries, but they can occur in the setting of multitrauma, particularly in unrestrained occupants in motor vehicle collisions and victims of severe assault. They rarely threaten the airway unless the anterior mandible is fractured, which allows the tongue to fall back and obstruct the airway. Usually, this obstruction is easily relieved by pulling the anterior segment of the mandible forward. This maneuver also remedies any interference with endotracheal intubation by the posteriorly displaced tongue. Patients with fractures of the angle of the mandible or the mandibular condyles often have limited mouth opening due to pain and to anatomic restriction. Because the deformity is bony, it is often not abolished by neuromuscular blockade (NMB). Although it is always important to establish the extent of mouth opening and whether it is adequate to permit intubation before administering NMB agents, this is especially true in patients with mandibular fractures.

Maxillary fractures usually occur in one of the classically described Le Fort patterns. Although the precise location of the Le Fort fracture pattern is sometimes difficult to remember, the Le Fort I, II, and III fractures can be thought of as follows (see Fig. 41-2). The Le Fort I fracture represents separation of the roof of the mouth from the face, with the fracture extending through the alveolar ridge to the base of the nose and separating the alveolar ridge and hard palate from the rest of the face. The Le Fort II fracture is separation of the central face from the rest of the face and cranium. The fractures extend from the base of the nasal bones through the medial orbits down through the maxilla to the posterior molars, effectively creating a free-floating central face fragment. The Le Fort III fracture is separation of the face from the skull. This fracture extends from the base of the nasal bones through the orbits to the lateral orbital rims and then through the zygomatic arch and down through the pterygoid plate.

Le Fort I fractures rarely cause airway compromise. If the fracture fragment has displaced posteriorly, it can easily be pulled forward by gripping the upper incisors or alveolar ridge. Le Fort II fractures similarly do not compromise the airway unless extensive hemorrhage is present. The fracture fragment, although free floating, rarely displaces posteriorly enough to compromise the airway. In the absence of hemorrhage, the mouth and oral pharynx are usually patent and functional. However, Le Fort III fractures can significantly compromise the airway due to posterior displacement of the entire central face, compromising the oral and nasal pharynx. Similarly, extensive swelling or hemorrhage related to the fractures may threaten the airway. In all cases, careful oral inspection and suctioning to determine the patency and adequacy of the oral cavity, followed by early intubation for airway protection and overall management of the patient, are advisable.

An uncommon but disastrous presentation of maxillofacial injury occurs when an attempted suicide fails because the gun (usually a shotgun) is oriented in such a way as to have the mass of the shot pass upward through the face rather than on a posterior trajectory through the brainstem. This often happens when the patient places a rifle or shotgun under the chin and then tries to reach downward for the trigger. This movement naturally leads to extension of the neck, and the trajectory of the missile is altered, causing it to pass upward through the face (Fig. 41-4). Although such injuries occur with massive facial distortion, airway management can range from easy to virtually impossible. Destruction of the mandible, tongue, palate, and nasopharynx often makes orotracheal intubation impossible, and hemorrhage is usually extensive. Primary surgical airway management is usually the method of choice. However, the injury can be predominantly anterior, sparing the airway, and the mandible and tongue can be displaced forward, permitting adequate oral access for orotracheal intubation. Nonetheless, efficient suctioning is usually required because the hemorrhage can be significant.