THE CLINICAL CHALLENGE

Effective airway management is a cornerstone of resuscitation of the critically injured patient. Although the nature and timing of airway intervention is influenced by assessment and prioritized management of multiple injuries, the fundamental principles of trauma airway management are no different than those applied to management of the airway in other complex medical situations. A consistent approach and a reproducible thought process will maximize success.

The requirement for intubation in a trauma patient depends on myriad factors that reach well beyond the airway. The indications for intubation, discussed in Chapter 1, include failure of the patient’s ability to maintain or protect the airway (as in traumatic coma). In such cases, the need for intubation is clear. Failure of ventilation or oxygenation is less common. The former is often related to intoxicants, head injury, or direct chest injury, such as pneumothorax or hemothorax. The latter may arise not only from direct chest trauma but also from pulmonary edema caused by diffuse capillary injury in the lung from shock (“shock lung”), or acute respiratory distress syndrome. One of the most common indications for intubation in trauma, however, is also the most challenging. This is the “anticipated clinical course” indication, wherein multiple injuries, need for imaging, hemodynamic instability, need for painful procedures or surgery, likelihood of deterioration, combative behavior, and other considerations lead to a decision to intubate—even though the airway itself, oxygenation, and ventilation are all adequate.

In the National Emergency Airway Registry (NEAR) database, the most common indication for intubation was traumatic head injury, accounting for 12% of all intubations—medical or traumatic.

APPROACH TO THE AIRWAY

Although many trauma intubations turn out to be straightforward, all should be considered at least potentially difficult. A targeted patient assessment should be performed with the aim of answering two fundamental questions. First: Will the procedure be difficult? Systematic use of the difficult airway mnemonics (Chapter 2) will help answer this question. Second: Will physiology suffer? This question prompts the clinician to anticipate predictable changes in physiology that may occur before, during, or immediately following intubation, as a result of the injuries present, the procedure itself, or the patient’s premorbid condition. Focusing on preintubation cardiopulmonary optimization (Chapter 20) will help mitigate adverse hemodynamic consequences of rapid sequence intubation (RSI).

Application of the difficult airway mnemonics (LEMON, ROMAN, SMART, and RODS) allows the clinician to rapidly identify the difficult airway at the bedside. It is worth noting that the LEMON mnemonic, originally published in the first edition of this manual, in 2000, is recommended as the airway assessment tool of choice in the current (ninth) version of advanced trauma life support (ATLS). The mnemonics are provided in detail in Chapter 2 but are adapted here specifically for airway management in the acutely injured patient:

1. L: Look externally. Injury to the face, mouth, or neck may distort anatomy or limit access, making the process of intubation difficult or impossible. Robust mask seal may be impaired by facial hair, external bleeding, preexisting physiognomy, or anatomic disruption (ROMAN). Injury to the anterior neck, such as by a clothesline mechanism or hematoma, may confound successful cricothyrotomy (SMART) or extraglottic device (EGD) placement (RODS).

2. E: Evaluate 3-3-2. In blunt trauma, the cervical spine is immobilized, and a cervical collar is usually in place at the time that the airway decisions must be made. While a cervical collar is not particularly effective at limiting cervical spine movement during intubation, it does greatly impair mouth opening, limiting both laryngoscopy and insertion of an EGD (RODS). The front portion of the collar should be opened to facilitate the primary survey and removed entirely during intubation, or cricothyrotomy, with manual in-line cervical stabilization maintained. Other injuries, such as mandibular fractures, may either facilitate or impair oral access, and mouth opening should be assessed as carefully as possible.

3. M: Mallampati. The trauma patient is rarely able to cooperate with a formal Mallampati assessment, but the airway manager should at least attempt to gently open the patient’s mouth as widely as possible and inspect the oral cavity for access, using a tongue or laryngoscope blade on the anterior portion of the tongue to gently flatten it and estimate oral access. At this time, potential hemorrhage or disruption of the upper airway may also be evident (RODS). It is important to refrain from “checking the gag reflex” during mouth opening, because this adds no useful information and may precipitate vomiting.

4. O: Obstruction, Obesity. Obstruction, usually by hemorrhage or hematoma, can interfere with laryngoscopy, bag and mask ventilation (ROMAN), or EGD placement (RODS). Obesity in the trauma patient presents the same challenges as for the nontrauma patient.

5. N: Neck mobility. All patients suffering blunt trauma require in-line stabilization of the cervical spine during airway management. By definition, in-line stabilization significantly impairs the ability to place the patient in the sniffing position, and as a result, direct visualization of the glottis will be predictably difficult. When in-line stabilization is required, other measures to improve glottic visualization such as optimal external laryngeal manipulation (OELM) or the use of video laryngoscopy should be used. Rescue devices (e.g., bougie, EGD, and surgical airway equipment) should be prepared as part of the overall airway management plan. Two areas of controversy are related to the need for spinal immobilization in patients suffering cranial gunshot wounds and those suffering penetrating wounds to the neck. In the former group, there is sound evidence that the amount of force delivered by a gunshot wound to the head or face in and of itself is insufficient to fracture the spine. In both groups, decision making should be guided by the neurologic examination. Simply stated, a normal neurologic examination is an indication that the neck can be gently moved to optimize visualization of the airway. A neurologic deficit suggestive of cervical spinal cord injury mandates in-line stabilization.

Special Clinical Considerations

The trauma airway is one of the most challenging clinical circumstances in emergency care. It requires knowledge of a panoply of techniques, guided by a reproducible approach (the airway algorithms), sound judgment, and technical expertise. In this section, we describe the considerations unique to several high-risk trauma airway scenarios (see Table 33-1).

As for any other anatomically distorted airway, application of the difficult airway algorithm will often lead to a decision to perform an awake intubation. In patients with signs of significant airway compromise (e.g., stridor, respiratory distress, and voice distortion), both the urgency of the intubation and the risk of using neuromuscular blockade are high. When symptoms are more modest, there is more time to plan and execute an airway intervention, but in neither case is delay advisable. The patient’s oxygenation should be assessed (i.e., “is there time?”), and it should be determined if RSI is advisable, likely under a double setup, even though the airway is difficult (see Chapter 3). This will depend on the clinician’s confidence about the likelihood of success of oxygenation using a bag and mask or an EGD, and intubation by direct or video laryngoscopy. Often, an airway not amenable to direct laryngoscopy (DL) can be managed using a video laryngoscope. In rare circumstances, a precipitous deterioration invokes the “forced to act” RSI principle (Chapter 3). In this circumstance, the need for immediate airway control outweighs the patient’s difficult airway attributes and permits a “one best attempt,” using neuromuscular blockade, with immediate recourse to a surgical rescue should that one attempt fail. When time permits and the airway is not obscured by blood, the best approach often is awake intubation using a flexible endoscope technique with sedation and topical anesthesia (see Chapter 16). This permits both examination of the airway and careful navigation through the injured area, even when the airway itself has been violated. This is especially true if a tracheal injury is suspected, because no other method of intubation allows the airway to be visualized both above and below the glottis. When the airway is disrupted, the endotracheal tube used should be as small as is reasonable to maximize the likelihood of success and to minimize the likelihood of additional airway injury.

Smoke inhalation can present on a spectrum from mild exposure to complete airway obstruction and death. The initial assessment should be designed to identify the presence or absence of high-risk historical features (e.g., closed space fire) and physical findings (e.g., singed nasal hairs, perinasal or perioral soot, carbon deposits on the tongue, hoarse voice, and carbonaceous sputum). When evidence of significant smoke inhalation is present, direct examination of the airway, often with intubation, is important. This is best done with topical anesthesia and token amounts of sedation (if required) using either a flexible endoscope or video laryngoscope. Both the devices permit evaluation of the airway and immediate progression to intubation, if indicated. Supraglottic edema is an indication for intubation, even if the edema is mild, because progression can be both rapid and occult. Observation in lieu of airway examination can be hazardous because the airway edema can worsen significantly without any external evidence, and by the time the severity of the situation is apparent, intubation is both required immediately and extremely difficult or impossible. If examination of the upper airway identifies that the injury is confined to the mouth and nose, and the supraglottic area is spared (normal), then intubation can safely be deferred, with subsequent examination at the discretion of the operator. If it is unclear whether edema is present, it is useful to periodically perform a repeated upper airway examination (e.g., 30 to 60 minutes), even if symptoms or signs do not develop or worsen.

In the NEAR studies, head injury is the most common indication for emergency department (ED) trauma airway management. Traumatic brain injury (TBI) is the number one cause of injury-related death worldwide. The principles of management of the patient with TBI and elevated intracranial pressure are discussed in more detail in Chapter 34.

When neurologic status is altered, by TBI or spinal injury or both, a rapid but thorough neurologic examination is important before any intubation attempt is undertaken, so that baseline neurologic status is documented to guide subsequent assessments and therapeutic decisions. Airway management decisions in the patient with severe TBI are centered on the prevention of secondary injury, that is, minimizing the magnitude and duration of hypoxia or hypotension. Secondary injury is the term applied when the insult to the injured brain is worsened by hypoxia, hypotension, or both.

Concrete steps can be taken to reduce the risk of secondary injury before, during, and after airway management:

First—Bring the principles of secondary brain injury prevention to the field. Emergency medical service providers should be educated and equipped to begin volume resuscitation and oxygen therapy before the patient arrives in the ED. Maintenance of adequate perfusion pressure (mean arterial blood pressure) and oxyhemoglobin saturation are the keys.

Second—Operators should focus on preintubation optimization and adequate brain perfusion before intubation. Appropriate volume replacement with normal saline solution, blood products, or both may mitigate or prevent hypotension. Selecting a hemodynamically stable and neuroprotective induction agent, such as etomidate, can further offset adverse hemodynamic consequences of RSI drugs and positive-pressure ventilation.

Third—Make wise decisions regarding RSI medications. Hemodynamically stable and neuroprotective induction agents, such as etomidate, are preferred. The dose should be reduced from 0.3 mg/kg to 0.15 mg/kg in the face of compensated or decompensated hypovolemic shock. Drugs that can precipitate hypotension (propofol, midazolam) should be avoided unless other options are unavailable. If the patient is severely compromised, ketamine is the agent of choice. The dose of ketamine is reduced to 0.5 mg/kg if the patient is in shock. Fentanyl, often used to optimize a hypertensive patient with presumed elevated intracranial pressure (ICP), is relatively contraindicated in polytrauma patients with marginal or low blood pressure even in the face of concomitant head injury.

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