Abstract
Airway management is of paramount importance in trauma resuscitations; in fact, virtually all management algorithms begin with the assessment and protection of the airway. Trauma airways are often compromised and among the most difficult to manage due to hemodynamic instability from multi-organ dysfunction, cervical trauma, or direct trauma to airway structures.
Airway management is of paramount importance in trauma resuscitations; in fact, virtually all management algorithms begin with the assessment and protection of the airway. Trauma airways are often compromised and among the most difficult to manage due to hemodynamic instability from multi-organ dysfunction, cervical trauma, or direct trauma to airway structures.
Important Considerations for Airway Management in Trauma Patients
Airway management in the trauma patient can pose many challenges, even for the most experienced clinicians. These factors can occur independently or collectively to complicate the care of the trauma patient. There are a few specific, unique aspects of trauma airway management that require special preparation and caution (Box 2.1).
Pre-existing difficult airway (anterior larynx, short neck, poor jaw mobility, etc.)
Physical constraints of trauma immobilization
Potential or actual injuries to the cervical spine
Mechanical distortion of the airway anatomy from direct trauma to oral, pharyngeal, or laryngeal structures
Mechanical distortion of the airway from injuries to contiguous structures (lower neck, thorax, or trachea)
Other non-airway factors such as hypotension, brain injury, or pneumothorax which compete with the urgency to control the airway
Hypoxia from underlying lung injury, such as pulmonary contusion
Consider Pre-existing Difficult Airway
A fundamental rule of airway management is to ensure caution when considering the paralysis of a patient who is expected to be a difficult or impossible intubation, unless the clinician has a specific plan to address a failed airway. Further, the ability to adequately mask ventilate should be considered when determining the type and method of airway intervention.
Trauma Immobilization
The physical process of trauma immobilization with a cervical collar and backboard can significantly limit access to the airway and the anterior neck. A properly placed collar limits mouth opening and intentionally prevents repositioning of the head and neck. If time allows, patients should be log rolled off a backboard, and providers should remove the cervical collar and utilize inline stabilization during intubation attempts.
Indications for Airway Intervention
The decision to intubate a trauma patient is among the most important and definitive steps in the management algorithm. The primary goals of airway management are to improve gas exchange, relieve respiratory distress by decreasing the work of breathing, and protection against aspiration (Box 2.2). Secondary goals range from the control of the agitated patient to the delivery of heated, humidified oxygen to facilitate core rewarming.1
Indications for Intubation
Oxygenation Failure: PO2 <60 on FiO2 >40%
Ventilation Failure: pH of <7.3 associated with hypoventilation or pCO2 >55 with previously normal pCO2 or rise in pCO2 by 10 acutely in COPD
Intentional Hyperventilation
Profound Shock: Reduces energy expenditure used during rapid breathing
Intentional Paralysis: To accomplish necessary procedures in a non-compliant patient
Aspiration Protection
Mechanical Obstruction
Core rewarming
Traumatic Injuries with Associated Difficult Airways
Closed Head Injury
Changes in hemodynamics, oxygenation, and ventilation should be minimized in an attempt to maintain adequate cerebral perfusion pressure (CPP).
CPP = MAP – ICP, where ICP is intracranial pressure and MAP is mean arterial pressure.
Laryngoscopy causes an increase in ICP secondary to its resultant hypertension.
The goal during intubation is to minimize the two main contributors to increased ICP – patient position and hypoventilation (Box 2.3).
Obtain a focused neurologic examination prior to intubation and the administration of sedatives and paralytics in an effort to guide further care.
Opiates, such as Fentanyl, may be given two-to-three minutes prior to intubation in an effort to blunt the sympathetic response.
Ketamine, etomidate, or propofol can be used as an induction agent.
Ketamine increases cerebral blood flow and counters systemic hypotension. Evidence suggests that it does not elevate ICP.
Although propofol can be used, it should be used with caution and with reduced doses in patients who are hemodynamically unstable.
Preparation: Ensure proper positioning, pre-oxygenation, and use apneic oxygenation with nasal cannula
Elevate the head of the bed to improve cerebral perfusion pressure and decrease aspiration risk
Premedication regimens are controversial. Fentanyl or esmolol may decrease catecholamine surge and control the hemodynamic response to intubation
Ketamine and etomidate are the best induction agents – with the least hemodynamic effects
Propofol has neuroprotective effects, but hypotension and decreased CPP can result
Post-intubation analgesia and sedation are essential – drips should be prepared prior to intubation to minimize the effects of agitation on ICP
Maxillofacial Trauma
Facial trauma can significantly distort normal anatomy, and injuries can range in severity from minimal to severe.
In cases where airway obstruction is either present or imminent, immediate decisive action is required. Alternatively, some patients initially present with minor respiratory difficulty, but pose a significant risk of rapid deterioration.
A few moments should be taken to plan an effective strategy to safely intervene without resulting in further harm.
Expectant management or delayed decision-making may force a cricothyrotomy.
Preparation including arrangements for back up plans significantly increases the chances of successfully securing the airway.
The patient’s neck should immediately be prepped for a surgical airway in the event of a likely difficult airway or failed intubation.
There is an associated cervical spine injury in up to 5% of patients with maxillofacial trauma and neurologic injury in up to 36%.2, 3
If there is no concern for C-spine injury, place the patient in an upright position to allow blood and secretions to drain. Check the oropharyngeal anatomy and ensure jaw mobility.
RSI is the initial method of choice – if not possible or contraindicated then a surgical airway should be performed (Box 2.4).
Preparation: Examine oropharyngeal anatomy and ensure jaw mobility. Rapidly devise a specific strategy
Can rapidly deteriorate – delayed decision-making may result in cricothyrotomy
Associated cervical spine and neurologic injuries can occur
RSI initial method of choice – if not possible or contraindicated then cricothyrotomy
Direct Airway Trauma
Important signs or symptoms of airway involvement include dyspnea, cyanosis, subcutaneous emphysema, hoarseness, and air bubbling through the wound site (Box 2.5).
Penetrating trauma has a high degree of morbidity and mortality; in fact, the overall mortality is as high as 11%,4 with up to 40% of patients requiring emergent intubation.5, 6
Zone I – between the clavicles and cricoid cartilage – is the least common neck injury, but the most likely to require emergent airway management due to the close proximity of major pulmonary and vascular structures.5
Tracheobronchial injury occurs in approximately 10–20% of patients with penetrating trauma to the neck.7–10
Indications for intubation in the setting of penetrating trauma include acute respiratory distress, airway compromise from blood or secretions, extensive subcutaneous emphysema, tracheal shift, or altered mental status.11
Gunshot wound to the anterior neck is also an indication for early intubation in order to prevent obstruction from an expanding hematoma.12
A stab wound to the anterior neck is an indication for early intubation only if there is evidence of vascular or direct airway trauma.13
Orotracheal intubation with RSI is the technique of choice in penetrating neck trauma12; however, administration of paralytics may result in an obstructed airway due to the relaxation of a damaged airway segment.
An awake airway evaluation or an awake intubation can be performed under sedation and topical anesthesia. Ketamine has been suggested as a good induction agent to use in this setting without paralytics.14
Occasionally the entrance wound provides a direct communication between the anterior neck and the trachea – in this case, it may be easier to intubate directly through the wound.
Blunt trauma to the neck is frequently more complicated as it is associated with a high incidence of C-spine injuries. Specifically, up to 50% of blunt airway trauma patients have concurrent C-spine injuries.15
In terms of securing the airway in patients with blunt neck trauma, there are essentially three initial methods of choice: RSI, awake intubation, and awake fiberoptic intubation. The exception occurs in a laryngeal fracture, in which emergent tracheostomy is the best first maneuver.
Important signs or symptoms of airway involvement include dyspnea, cyanosis, subcutaneous emphysema, hoarseness, and air bubbling through the wound site
Indications for intubation in penetrating trauma include acute respiratory distress, airway compromise from blood or secretions, extensive subcutaneous emphysema, tracheal shift, or altered mental status
GSW to the anterior neck is an indication for early intubation due to expanding hematoma; stab wounds need intubation only if there is evidence of airway or vascular trauma
Awake airway evaluation or intubation can be performed with sedation (Ketamine) and topical anesthesia
Blunt neck trauma has a high incidence of associated cervical spine injury
Cervical Spine Injury
All trauma patients who present with cervical spine precautions should be assumed to have a cervical spine injury until proven otherwise (Box 2.6).
The two initial methods of choice for securing the airway are oral intubation with RSI or awake fiberoptic intubation.
When performing RSI, the anterior portion of the collar should be removed to allow for manual in-line axial head and neck stabilization (MILS).
MILS has been shown to immobilize the c-spine better in the setting of endotracheal intubation than the c-collar alone.16
However, MILS can make intubation attempts difficult, and it may not reduce the risk of cervical spine movment.17, 18
Consider airway adjuncts such as using video assisted laryngoscopy to improve the chance of success while maintaining MILS.
All trauma patients should be assumed to have a C-spine injury until proven otherwise
RSI or awake fiberoptic intubation are the preferred methods
When performing RSI, the anterior portion of the cervical collar should be removed to allow for manual in-line stabilization
Consider airway adjuncts to improve chances of success while maintaining manual in-line stabilization
Thoracic Trauma
Thoracic trauma may present difficulties when it causes a distortion of the trachea from its normal midline position (Box 2.7).
Occasionally a large pneumothorax can cause significant subcutaneous emphysema tracking into the neck, which can interfere with the ability to identify the trachea and/or cricothyroid membrane.
Pneumothorax, hemothorax, or significant trauma to the lung (pulmonary contusion) can inhibit the ability to adequately pre-oxygenate the patient prior to the intubation.
A pneumothorax should be treated prior to intubation if possible.
Thoracic trauma can displace the trachea from the normal midline position or distort the normal anatomy and landmarks
RSI or awake fiberoptic intubation are the preferred methods
Thoracic injuries can inhibit pre-oxygenation
Treat pneumothorax prior to intubation if able
Burns
Upper airway edema is progressive over 24–36 hours after the burn; therefore, it is advisable to secure an airway earlier rather than later (Box 2.8).
Because burn injuries develop over hours, it is often is reasonable to consult a burn specialist prior to securing an airway when appropriate.
If transport is needed to a burn center, particularly a prolonged transport, consider a secure airway with intubation prior to transfer.
Indications for intubation include: Stridor or hoarseness, known inhalation of toxic fumes, and increased work of breathing. Nasopharyngoscopy by the treating clinician or an ENT consultant can help to look for evidence of burns or edema of the posterior pharyngeal or glottis structures. If no burns to these structures are discovered and the patient remains stable, intubation can be withheld. Remember, however, that this is a dynamic situation. Any change with respect to the patient’s work of breathing or stridor should prompt another nasopharyngoscopic evaluation or definitive airway management with intubation.
Standard oral endotracheal intubation with RSI is the initial method of choice to secure the airway when no obvious obstruction is visualized.
If concerned about obstruction, “an awake look” should be performed under sedation and topical anesthetics.
Because of the incidence of upper airway edema, there should be a low threshold for moving to fiberoptic intubation or cricothyrotomy.
Upper airway edema is progressive over hours – advisable to secure an airway early, but reasonable to consult with burn specialist in many circumstances
Liberal use of nasopharyngoscopy can help with the decision to intubate or manage expectantly
If prolonged transport is needed to a burn center, consider a secure airway prior to transfer
RSI is the method of choice, but could also consider awake intubation or fiberoptic intubation
Indications for intubation:
Stridor or hoarseness
Known inhalation of toxic fumes
Increased work of breathing
Burn or edema to airway structures
Carbonaceous sputum or soot in nares or mouth
Rapid-Sequence Intubation (RSI)
RSI is currently considered the method of choice for emergent airway control in the trauma patient, unless specific contraindications are present (Box 2.9).19–21
Total upper airway obstruction requiring surgical airway
Loss of facial/oropharyngeal landmarks requiring surgical airway
Relative Contraindications:
Anticipated difficult airway scenario where endotracheal intubation may not be successful, relying on bag-valve-mask
Crash airway scenario with the patient in a cardiac arrest situation, unconscious, and apneic, which requires immediate intervention with no medications
Rapid Sequence Intubation (RSI): The Technique
A teaching tool to describe the steps of RSI was developed by Walls.21 The “P’s” of RSI are described below in a modified form that reflects emphasis on some new considerations.
P – Plan B
The first P in this series refers to the predetermined plan for dealing with a difficult or failed orotracheal intubation. A complicated situation can rapidly become a disaster if no pre-implemented plan is in place to mitigate unanticipated difficulty. An emergency airway cart, containing difficult intubation equipment, can keep all needed tools readily available. See Box 2.10 for an example emergency airway cart.
Emergency Airway Supplies (example)
A complete set of RSI drugs
Induction/Sedation agents: Etomidate, ketamine
Paralytic agents: Succinylcholine, rocuronium, vecuronium
Adjunctive medications: Atropine, lidocaine
Various ET tube sizes and types: Pediatric and adult
Oropharyngeal and nasopharyngeal airways
Additional laryngoscope parts
Miller and Macintosh blades
Standard laryngoscope handle
Pediatric laryngoscope handle
Video laryngoscopy tools
GlideScope
C-Mac
Airtraq
Airway Adjuncts
Tracheal Introducer (Bougie)
LMA – laryngeal mask airway
ILMA – intubating LMA
King LT
Retrograde intubation sets
Surgical Airway Tools
Percutaneous and open cricothyrotomy kits
Scalpels (#10, #11, #15 blades)
Extra instruments
Various size needles and syringes
P – Predict a Difficult Intubation
A thorough evaluation of the patient prior to attempts at laryngoscopy can help to predict a difficult intubation. The LEMON law can be used as a tool for airway evaluation. The description below adds “S” for saturation.
By discussing out loud your primary plan, your plan B, and the conditions which will mandate an emergent cricothyrotomy, it will make it easier to move to cricothyrotomy if indicated.
L – Look Externally
External anatomical features that can predict difficult intubation are short muscular neck, protruding upper incisors, high-arched palate, receding mandible, and severe facial trauma.
E – Evaluate Internally: The 3-3-2 Rule
The rule describes the ideal external dimensions of the airway.
3 – the opening of the jaw should be far enough to accommodate three fingers (3–4 cm).
3 – the distance from the mentum to the hyoid bone should be at least three fingerbreadths.
2 – the distance from the floor of the mouth to the thyroid cartilage should be at least two fingerbreadths.
M – Mallampati
The Mallampati classification was developed to correlate a simple visual inspection of the patient’s pharynx with the ability to obtain direct visualization of the larynx. Airways are designated as Class I, II, III, or IV. Mallampati classes roughly correlate with the Cormack and Lehane direct laryngoscopic views, graded as 1, 2, 3, and 4 (Figure 2.1).
Figure 2.1 Mallampati classification
Mallampati Class I: No difficulty: Soft palate, uvula, fauces, pillars visible
Mallampati Class II: No difficulty: Soft palate, uvula, fauces visible
Mallampati Class III: Moderate difficulty: Soft palate, base of uvula visible
Mallampati Class IV: Major difficulty: Hard palate only visible
O – Obstruction
Blood in the upper airway, foreign body, expanding hematoma, abscess, swelling of intraoral structures, or laryngeal edema.
N – Neck mobility
Inability to flex or extend the neck (c-collar, arthritis, etc.), Cervical spine injury.
P – Prepare
Preparation includes the following:
Remove dentures.
Bring the difficult airway cart to the bedside.
Have the chosen intubation method set up.
Verify the integrity of the balloon on the ET tube.
Have suction ready at the bedside. When preparing suction, it is useful to have two suction options available. A standard Yankauer tip works well for loose secretions but does not adequately aspirate larger food pieces.
Verify the integrity of IV access.
Have color-change capnography and/or end-tidal CO2 device ready.
P – Preoxygenate
As early as possible the patient should be placed on high flow oxygen, as close to 100% FiO2 as possible (Figure 2.2). A typical NRB mask with oxygen reservoir can only provide an FiO2 in the mid 60% range. The FiO2 can be substantially raised by placing a nasal cannula set at 15 LPM on the patient during the preoxygenation period. A full 15 LPM can be effectively delivered via a standard cannula.22 A non-rebreather mask with a reservoir is then added over the nasal cannula and set at the absolute maximum possible setting. This means that the oxygen flow knob will be turned until it will not turn any further. During the intubation procedure, the mask is removed, but the nasal cannula is left in place during intubation. Passive oxygenation, also known as apneic oxygenation, provides real oxygen delivery to the patient and can help maintain saturations above 90% for an extended period of time.22, 23 Patients should be positioned sitting up during pre-oxygenation, as patients will have less ventilation/perfusion mismatch compared to lying flat.
P – Position
Many trauma patients present in a c-collar (Figure 2.3). After collar removal, the c-spine should be maintained with manual in-line stabilization. If the patient’s c-spine can be cleared, the patient should be placed such that the head is elevated off the bed by a few inches (approximately four inches). The head is subsequently extended on the neck so that the face is parallel to the ceiling, while the earlobe is aligned with the sternal notch.22 This maximizes the alignment of the oral axis, pharyngeal axis, and the glottis axis. Except in the pediatric patient, placing the pillow or towel roll beneath the shoulders to force hyperextension of the neck without elevating the head is not helpful, and should be avoided.
Figure 2.3 Positioning (Photos: Colin Kaide)
Proper positioning with earlobe in line with sternal notch and face parallel to the floor (used with permission, courtesy of Colin Kaide)
Proper positioning with earlobe in line with sternal notch and face parallel to the floor using multiple blankets
Incorrect positioning with earlobe not in line with sternal notch and neck hyperextended
P – Put to Sleep
Induction agents are given simultaneously to or in rapid succession with paralytic agents (Table 2.1).
Cricoid pressure (Sellick’s Maneuver) is no longer recommended routinely. It has no proven benefits and can potentially make intubation more difficult.24
Avoid ventilating the patient until reoxygenation is required, as indicated by oxygen saturation falling below 90%.
Etomidate | Ketamine | Propofol | |
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Dosage | IV 0.3 mg/kg IV 0.15 mg/kg in hypotensive patients | IV push 1–2 mg/kg, with decreased doses in hypotension | Adult and Children: 2–2.5 mg/kg IV slowly over 30 sec; with decreased doses in hypotension |
Pregnancy Category | C | Unknown, but likely safe | B |
Preparation | 2 mg/mL | 100, 50, and 10 mg/mL | 10 mg/mL |
Description | Non-barbiturate, sedative hypnotic with anesthetic and amnestic properties (no analgesia) | Dissociative anesthetic; PCP derivative. May act at multiple receptor sites including opioid and cholinergic Ketamine is the only single agent with anesthetic, amnestic, and analgesic properties | Non-barbiturate, sedative-hypnotic with anesthetic and amnestic properties |
Onset & Duration | <60 sec; 6–10 min | IV 30–60 sec; 10–15 min | <60 sec; 5–10 min |
Reversal Agent | None | None proven; naloxone and physostigmine may have some theoretical effect | None |
Ideal Patient |
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Contraindications |
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Major Side-Effects |
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P – Paralyze
Depolarizing agents such as succinylcholine act at the ACh receptor and act to initially cause depolarization of the motor endplate and induce contraction, manifesting clinically as fasciculations (Table 2.2).
Subsequently, the receptor is blocked by the succinylcholine, preventing ACh from binding and producing further contraction. The paralysis lasts until succinylcholine is degraded by acetylcholinesterase.
Non-depolarizing agents such as vecuronium and rocuronium competitively inhibit the ACh receptor, occupying it and then exiting the site. These agents are removed from the neuromuscular junction and broken down in the liver. Their duration and onset of action are generally longer than succinylcholine. Vecuronium is not ideal for RSI and is best used for ongoing paralysis.
Succinylcholine | Rocuronium | |
---|---|---|
Dosage | 1.5–2 mg/kg IV rapid push | 0.6–1.2 mg/kg IV rapid push. 1 mg/kg is preferred dose |
Pregnancy Category | C | B |
Preparation | 20 mg/mL | 10 mg/mL |
Description | Depolarizing neuromuscular blocking agent | Non-depolarizing neuromuscular blocking agent |
Onset | 30–60 sec | 45–90 sec |
Duration | 6–12 min | 15–40 min |
Reversal Agents | None | Neostigmine, Sugammadex |
Ideal Patient | First-line paralytic agent in RSI |
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Contraindications |
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Major Side-Effects |
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P – Pass the Tube
One technique which has been described to facilitate direct visualization of an anterior larynx is called “BURP” (Backward-Upward-Rightward-Pressure).25, 26 The assistant applies pressure to the thyroid cartilage, first backward (toward the table), then upward (toward the head), and finally rightward. The adult larynx should be displaced backward so as to abut the vertebrae, 0.5–2 cm to the right and about 2 cm cephalad. Meanwhile, the intubator attempts direct visualization of the larynx.
External Laryngeal Manipulation (ELM) achieves the same backward, upward, and rightward airway repositioning as does “BURP,” however the pressure is applied by the intubator with his or her right hand.27, 28 This allows the intubator to visualize the effects of the manipulations and adjust the pressure accordingly. The final position of the larynx can be held by the assistant, freeing the intubator’s right hand to complete the procedure (Figure 2.4).
Video Laryngoscopy
The introduction of video laryngoscopy has virtually made most other airway devices obsolete. This device uses a fiberoptic lens attached to the laryngoscope blade or at the end of a stylet to transmit a picture of the cords to a portable LCD screen. Direct visualization of the tube passing through the cords can be obtained.
The GlideScope
Unlike with a conventional laryngoscope, the GlideScope blade is inserted in the middle of the tongue without a sweeping motion.
Owing to the steep curvature of the blade, the cords can be easily seen, even in an anterior airway.
Occasionally, the cords and tube can be seen, but difficulty arises in trying to pass the tube through the opening. Passage of the tube can be made easier by using the rigid GlideScope stylet.
The C-MAC
Conceptually similar to the GlideScope, but the C-MAC uses a blade configured much like a conventional Macintosh blade, whereas the glidescope blade has a more hyperacute angle.
The CMAC can be used to perform DL, with the back-up of having a video view of the cords.
One study suggested that the C-MAC and GlideScope both provided good views of the cords, however use of the C-MAC resulted in faster times to passage of the tube successfully through the cords.29