An Advanced Life-Support Emergency Services unit brought a 35-year-old male into the emergency department (ED) “backboarded and collared.” The patient was an unrestrained driver who was ejected from his car when it ran off the road and hit a tree. When a paramedic team arrived 10 minutes after the crash, the patient had a blood pressure (BP) of 90/50 mm Hg, heart rate (HR) 100 beats per minute (bpm), respiratory rate (RR) 20 breaths per minute, and oxygen saturation (SpO₂) 95% on room air. His Glasgow Coma Scale (GCS) score was 7 (opened eyes to pain—2, moaned—2, abnormal flexion—3). Pupils were equal and reactive, and his mouth was tightly clenched. The patient was given oxygen via nasal prongs and a non-rebreathing face mask. Although the patient exhibited episodic agitation with combative behavior during transport, intravenous (IV) access was obtained and an infusion of Lactated Ringer’s was begun.

After ensuring scene safety, the immediate management of the patient with traumatic brain injury (TBI) in a field setting should focus on stabilizing and maintaining oxygenation and blood pressure. All patients with head injuries have potential cervical injury and should be assessed for the need to be immobilized. A fundamental premise in pre-hospital care is to anticipate and prepare for eventualities such as vomiting, seizures, and aberrations of blood pressure or oxygenation.

Should Tracheal Intubation be Performed in the Field for This Patient?

In this patient, ensuring oxygenation via a patent airway is of paramount importance. Indications for a field tracheal intubation include inadequate ventilation or oxygenation despite supplemental oxygen administration, or the inability of the patient to protect the airway. A relative indication for intubation is the risk of losing the airway during transport. Transport time and type, for example, ground versus aeromedical, must be considered. Studies of the outcome of pre-hospital airway management have yielded conflicting results leaving little consistent evidence indicating a benefit to field tracheal intubation in most patients with head injury who are oxygenated and ventilating^1–7; as discussed in Chapter 16, pre-hospital airway management protocols are currently being further investigated.

In the case presented, the patient was maintaining oxygenation and ventilation. His clinical course could not be certain and it was reasonable for the field team to consider tracheal intubation. However, the patient had clenched teeth and was predicted to also pose difficult direct laryngoscopic intubation based on his short neck and cervical spine (C-spine) immobilization. A decision to intubate would involve the use of a rapid sequence intubation (RSI) protocol; considering the short transport time, field RSI was not indicated.

What Additional Considerations Are Imposed by Field Conditions?

Several other priorities in clinical care must be addressed by the field team after initial patient stabilization.

Circulation

Hypotension is a critical factor associated with an increased morbidity and mortality in patients with head injuries.^8,9 Blood pressure in the field should be monitored closely with the goal of avoiding or correcting hypotension (systolic BP <90 mm Hg in adults).¹⁰ This patient presented with a field BP of 90/60 mm Hg. With the poor outcome associated with hypotension in TBI patients, fluid resuscitation becomes a priority. However, the field team must weigh the benefit of securing IV access in the field with the risk of delayed transport to a trauma center. Ideally, IV access and fluid administration should occur during expeditious transport to the trauma center. It should be emphasized that isolated brain injury rarely accounts for hypotension in trauma patients with multisystem injury¹¹; rather, if present, as with this patient, hemorrhage elsewhere must be suspected.

Neurologic Disability: Intracranial Pressure (ICP) and C-Spine

ICP: The GCS of 7, 10 minutes after the injury, is not predictive of the patient’s clinical course or prognosis (other than an increased likelihood of C-spine injury). The patient did not have unequivocal evidence of increased ICP since the pupils were equal and reactive and the motor response was decorticate, not decerebrate. As such there was no indication for paramedics to provide any field intervention for managing elevated ICP with modalities such as tracheal intubation/hyperventilation, mannitol, or hypertonic saline.^12–14

A potential pitfall in the management of the TBI patient is to assume that trauma is entirely responsible for altered mental status. Consideration must be given to the reversible causes of altered mental status, for example, hypoglycemia and drug toxicity, in addition to hypoxemia and hypotension.

C-spine immobilization: All patients with blunt trauma to the torso or neurological dysfunction should be suspected of having spinal cord injury until proven otherwise. Although neurologic impairment is fully manifest at the time of injury in most patients with vertebral injury,¹⁴ the implications of an unidentified spine injury are such that routine use of immobilization devices is indicated. Secondary neurological injuries are reported to occur in 10% to 30% of patients with delayed diagnosis who are not immobilized at time of entry into care^15,16 and in 2% to 10% of those who are immobilized.¹⁷ Three studies suggest that the probability of associated C-spine injury is at least tripled with GCS scores of 8 or less.^18–20 Research into techniques for optimal cervical immobilization supports the use of a rigid cervical collar that incorporates the upper thorax, stabilization blocks on either side of the head, and a long spine board for transport.^21,22 Spinal immobilization is not without consequence in that patients are at risk of aspirating if they seize, vomit, or lose protective airway mechanisms. In addition, collars have consistently been demonstrated to increase ICP and may worsen ICP dynamics in patients with head injury,^22–26 probably by interference with cerebral venous drainage.²⁷ Finally, spinal immobilization has the potential to complicate airway management by worsening the laryngeal view obtained at direct laryngoscopy (DL).²⁸ With the history of TBI and GCS of 7, the presented patient was at significant risk of C-spine trauma and required full C-spine immobilization.

Analgesia/Sedation

Patients with severe head injuries can experience episodes of agitation and combativeness, both of which tend to increase ICP and can pose safety risks to both the patient and the paramedic crew. Sedatives, such as benzodiazepines and opioid analgesics, are typically employed but, if given, the GCS score should first be determined, and the status of oxygenation and ventilation closely monitored after administration.

Transport Decisions

An early priority in the management of patients with moderate or severe brain injuries is transportation to the closest facility providing immediate access to neuroimaging and neurosurgical services. Patients with severe TBI transported to trauma centers without the availability of prompt neurosurgical care are at risk of a poor outcome.⁹ For example, acute subdural hematomas in patients with severe TBI are associated with a 90% mortality if evacuated more than 4 hours after injury, but only 30% mortality if evacuated earlier.^29,30 Consequently, it is recommended that field Emergency Medical Services (EMS) systems operate under strict ground and aeromedical trauma transport protocols. Commonly accepted criteria for transport of head injured patients to a trauma center include severity of injury, a respiratory rate <10, systolic blood pressure <90 mm Hg, and a GCS score <12.

The ambulance arrived at the emergency department (ED) after a 15-minute transport. While the patient was being transferred onto the gurney in the trauma bay, it was noted that he was obese (5′ 8″ [172 cm], 275 lb [125 kg], BMI 42.3 kg·m⁻²); he had blood coming out of his right ear, and his cervical collar was riding high around his short neck. His BP was now 130/80 mm Hg, HR 110 bpm, RR 24 breaths per minute, SpO₂ was 90% on a non-rebreathing face mask, and he had snoring respirations. His blood sugar was 110 mg/dL (6.1 mmol·L⁻¹). His GCS score had decreased to 6 (2 for opened eyes to pain only, 2 for moans, and 2 for intermittent decerebrate posturing). At this point, it was noted that his right pupil was 8 mm and unreactive; his left pupil was 4 mm and reacted sluggishly. A quick airway evaluation revealed that his teeth were still clenched; he had a 6-cm thyromental span and 4-cm hyothyroid distance. There was no evidence of blunt trauma to the neck, and the cricothyroid membrane was identifiable and palpable in the midline. Two large-bore IVs were secured, blood was drawn and sent for chemistries and type and cross match. The hematocrit on the venous blood gas was 45. Portable chest and pelvis radiographs in the trauma bay were normal. Cross-table lateral x-ray of the C-spine showed good alignment and no pre-vertebral soft tissue swelling. A focused assessment with sonography in trauma (FAST) examination of the abdominal was performed, which showed no free fluid in the abdomen. A stat neurosurgery consult was ordered. Personnel from diagnostic imaging called, saying that they were ready to image the patient once he was stabilized. While the trauma team was deciding the best approach to securing the airway and managing the suspected increased ICP, the patient had a 30-second tonic–clonic seizure and desaturated to an SpO₂ of 80%.

What Elements of Airway Management Must be Considered in This Patient?

The immediate priority in this patient is reoxygenation, given the evidence suggesting a worsening of prognosis with hypoxemia in the patient with TBI.^8,9 The patient should receive assisted face-mask-ventilation (FMV) with 100% O₂. Once the SpO₂ is again well above 90%, attention can be turned to formulating a plan for tracheal intubation. Unless the seizure spontaneously terminates within 1 to 2 minutes, pharmacologic intervention with lorazepam would be indicated.

From the perspective of airway management, trauma patients secured on a backboard with cervical immobilization can appear intimidating. Notwithstanding, formal airway assessment may point to little anticipated difficulty (see sections “Difficult BMV: MOANS,” “Difficult DL Intubation: LEMON,” “Difficult VL Intubation: CRANE,” “Difficult Use of an EGD: RODS,” and “Difficult Cricothyrotomy: SHORT” in Chapter 1). In this case, the patient’s obesity predicts an increased likelihood of difficult FMV.^31–33 DL may be difficult due to the patient’s short neck and the C-spine immobilization: manual in-line neck stabilization (MILNS) increases the likelihood of obtaining a poor (e.g., Cormack/Lehane [C-L] Grade 3) view during direct laryngoscopy.³⁴ Any trismus will likely resolve with muscle relaxant administration, if used. Extraglottic device (EGD) insertion may be difficult, but should succeed once pharmacologic paralysis is achieved. Finally, although obesity can make transtracheal access difficult, in this patient, the cricothyroid membrane was easily palpable, suggesting easy access.

How Are You Going to Proceed with Tracheal Intubation?

With a reasonable expectation of successful direct laryngoscopic intubation and the availability of a backup plan “B” (e.g., indirect videolaryngoscopy, FMV, EGD use, or cricothyrotomy) should intubation fail, RSI should be used in this uncooperative patient. This plan confers the advantages of optimal intubating conditions with skeletal muscle relaxation while helping to mitigate any laryngoscopy and intubation-induced increases in ICP through the use of narcotic and sedative–hypnotic induction medications.

What Are Your Goals During Tracheal Intubation of the TBI Patient with C-Spine Precautions?

Our goals are to achieve tracheal intubation expeditiously while avoiding secondary neurologic injury by (1) maintaining oxygenation; (2) avoiding decreases in cerebral perfusion pressure (CPP); and (3) minimizing movement of the head and neck. Attention must also be directed toward prevention of gastric content aspiration during the process.

How Are CPP, ICP, Cerebral Blood Flow (CBF), and Autoregulation Related; What Changes Occur in TBI and How Can We Modify These Changes?

Elevated ICP is associated with worse outcomes in TBI. While its early recognition and management have not been conclusively linked to improved outcome, it is prudent to avoid any further increases in ICP in the brain-injured patient.

ICP reflects the state of the contents of the fixed housing of the intracranial vault. The three normal contents of the vault are brain tissue, cerebrospinal fluid (CSF), and blood. Intracranial blood volume is directly related to CBF. This flow is normally kept relatively constant over a wide range of blood pressures by cerebral autoregulation; as blood pressure varies, cerebral vasoconstriction or vasodilatation occurs to maintain constant blood flow, and in turn volume. However, the brain’s ability to autoregulate blood flow over a range of blood pressures is impaired or lost in TBI.

A second mediator of CBF is blood carbon dioxide tension. As blood carbon dioxide tension rises, so will CBF, leading to increased intracranial blood volume and thereby increased ICP. While aggressive hyperventilation in the patient with TBI is no longer recommended in the absence of signs of brain herniation,^9,35 attention should be paid throughout the airway management process to maintaining normocarbia.¹³

CPP is the driving force for blood flow to the brain, and is measured by the difference between the mean arterial blood pressure (MAP) and the ICP, so that CPP = MAP – ICP. In the patient with disrupted autoregulation, decreases in MAP will decrease CPP while increases in MAP, if not accompanied by equivalent increases in ICP, may be beneficial because of the increase in driving pressure for oxygenation of brain tissue. It is generally recommended that the ICP be maintained below 20 mm Hg, MAP between 100 and 110 mm Hg,³⁵ and CPP at or above 70 mm Hg. Hypotension leading to a decrease in CPP, even for a very brief period, is especially harmful, and as already mentioned has been shown to be an independent predictor of increased mortality and morbidity in patients with a TBI.^8,9

How Does Airway Management Affect ICP Dynamics?

Laryngoscopy and intubation may cause an increase in ICP indirectly through an increase in blood pressure (with disrupted autoregulation) or through a direct effect on ICP. Both laryngoscopy and placement of an endotracheal tube (ETT) result in afferent discharges that increase sympathetic activity and release of catecholamines, that is, the reflex sympathetic response to laryngoscopy (RSRL). A catecholamine surge may occur, especially with multiple attempts at laryngoscopy, potentially leading to increased heart rate and blood pressure. In the patient with TBI who has impaired autoregulation, such a blood pressure surge may contribute to an increase in ICP. This fact underscores the importance of using drugs such as sedative-hypnotics and opioids to mitigate the RSRL.

What Effects on ICP Can be Expected from Medications Commonly Used During Airway Management in the ED?

Pharmacologic agents used to aid in airway management must be selected with consideration of their effects on CPP. Prior to intubation, a modest fluid bolus will help maintain blood pressure, while vasopressors such as ephedrine or phenylephrine should also be immediately available to treat post-intubation hypotension. Pretreatment, induction, and paralytic agents used to attenuate a rise in ICP and/or facilitate intubation in the patient with TBI have been discussed in detail in Chapter 4. It should be noted that if a longer-acting muscle relaxant is used to facilitate tracheal intubation or maintain post-intubation paralysis, formal monitoring for further seizure activity should be instituted in this patient.

Victims of major trauma often require several interventions, including definitive airway control, before a full assessment of the C-spine is possible. Without radiographic evidence of an intact C-spine, an unstable injury should be assumed and airway management undertaken accordingly.

What Range of C-Spine Movement Is Considered Within Physiologic Limits?

In order to interpret the data on the effects of airway manipulations on movement of the C-spine, the amount of motion that would indicate spinal instability should be defined. Panjabi et al. have suggested that horizontal motion (anteroposterior [A-P] displacement) of one vertebral body on another exceeding 20% of vertebral body width (or 3.5 mm in an adult, corrected for x-ray magnification); >11 degrees of relative angulation of adjacent cervical vertebrae, or >1.4 mm of distraction on resting lateral radiography of the sub-axial C-spine is abnormal and would indicate instability.^36–38 Preexisting cervical abnormalities such as spinal stenosis could increase the risk of neurologic consequences inside these “anatomic limits.”³⁹

What Effect Does DL and Intubation Have on Movement of the Normal C-Spine?

Radiographic studies on live and cadaveric subjects with intact C-spines demonstrate that DL causes considerable extension between the occiput and C2. Most extension (about 12 degrees) occurs between the occiput and C1, with about half as much (approximately 7 degrees) between C1 and C2.^40–51 A total of about 6 degrees of extension occurs from C2 to C5.^{41–44,50,51} From C5 to the cervicothoracic junction, a small amount (about 8 degrees) of flexion occurs.^42–44 Actual tube passage causes slight additional superior rotation between the occiput and Cl, but little other movement.^40,50 There is some evidence that exposing only a “minimum view” during laryngoscopy (i.e., seeking a view of only the posterior elements of the laryngeal inlet, but not of the cords) will reduce occiput–C2 extension.^40,50,52,53

What Effects Do Airway Opening Maneuvers and FMV Have on Movement of a Normal C-Spine?

Several radiographic studies have looked at the effects of airway opening maneuvers and FMV on C-spine movement. One cadaver study performed with no applied MILNS found that chin lift and jaw thrust caused as much extension at C1–C2 as oral laryngoscopic intubation.⁵⁴ A second cadaver study, using backboard, cervical collar, and tape found that significantly more C-spine displacement occurred with FMV than with either oral or nasal tracheal intubation.⁵⁵ However, a subsequent study using elective surgical subjects with their heads taped in a neutral position found FMV to cause significantly less C-spine movement than DL at each of the occiput–C1, C1–C2, C2–C5, and C5–T1 motion segments.⁴⁴ Although sometimes conflicting in their results, these studies can at least be taken as an indication that appropriate C-spine precautions should be applied during all phases of airway management in patients at risk of C-spine injury.

What Are the Effects of Airway Opening Maneuvers and FMV in Models of an Injured C-Spine?

Donaldson et al.⁵⁴ studied the motion occurring during various airway maneuvers in a series of six cadavers with a surgically created unstable C1–C2 segment. With the head stabilized, they found that pre-intubation maneuvers (chin lift and jaw thrust) caused more narrowing of the space available for the spinal cord (SAC) than DL or blind nasal intubation. In a subsequent cadaver series, this time with an unstable C5–C6, the same investigators demonstrated a trend toward chin lift/jaw thrust causing as much movement as DL.⁵⁶ Aprahamian et al.⁵⁷ also studied a cadaveric specimen with a posteriorly destabilized C5–C6 segment, and similarly reported that chin lift/jaw thrust caused as much or more movement at the site of injury as oral or nasal intubation. Brimacombe et al.⁵⁸ determined C-spine motion for six airway management techniques in cadavers with a posteriorly destabilized third cervical (C3) vertebra. Here again, both chin lift/jaw thrust and oral intubation with DL caused significant antero-posterior (A-P) displacement of the unstable segment, although the movements were within the previously described physiologic limits. Finally, Pasarn et al. studied nine lightly embalmed human cadavers with a surgically created unstable C1–C2 injury, comparing the motion caused by a jaw thrust maneuver with that resulting from a head tilt/chin lift. Using electromagnetic motion sensors attached directly to the spine above and below the injury level, they found that head tilt/chin lift caused significantly more angular motion in all planes, and more axial displacement and A-P translation than the jaw thrust maneuver.^43,59,60

How Effective Is MILNS in Preventing C-Spine Motion in Normal Patients and Injury Models?

MILNS appears to restrain overall spinal movements occurring during DL in patients and cadaveric specimens with normal spines to within physiological levels, and has less impact on airway interventions than do other forms of immobilization.^41,53,61 In injury models, Lennarson et al.^50,62 reported that MILNS did not completely eliminate movement at the injury level during intubation of a cadaver model with either posterior or complete ligamentous C4–C5 disruption; however, the movements recorded during interventions were within physiological limits. Gerling evaluated the effect of MILNS as well as cervical collar immobilization on spinal movement during DL in a cadaver model with a C5–C6 transection injury. Although there was less A-P displacement measured with application of MILNS compared with collar (7.5% of vertebral body width vs. 13.7%), the overall magnitude of movement was small and within physiological range. There was no difference in axial distraction or angular rotation.⁶³ Turner studied 10 cadavers surgically destabilized at C4–C5. MILNS did not significantly change the median motion seen during DL in any of angulation, distraction, or A-P displacement at the unstable level.³⁹

Two recent comprehensive reviews on the topic support the notion that while there may be some reduction in overall C-spine motion with MILNS, movement at individual motion segments, including sites of injury, may in fact not be significantly restrained by stabilization.^28,64 As Aprahamian et al.⁵⁷ stated about collar immobilization in 1984, it may be that MILNS should simply be taken as a cautionary sign of a possible neck injury, and to then use gentle and precise airway maneuvers to minimize C-spine movement.⁶⁴

How Does Applied MILNS Impact DL?

Many trauma patients presenting to the ED arrive on a backboard immobilized with rigid cervical collar, sands, and tape. Unfortunately, any immobilization technique that restricts mouth opening will make laryngoscopy more difficult. In one study, 64% of patients immobilized with a collar, tape, and sandbags presented at Grade 3 or 4 view with DL, compared to only 22% of patients undergoing MILNS, with cervical collar removed.³⁴ Other studies concur that DL in patients stabilized with cervical collars will result in a >50% incidence of C-L Grade 3 or 4 views.^63,65 Goutcher and Lochhead⁶⁶ studied the effect of semirigid cervical collars on mouth opening in awake volunteers. Mean mouth opening of 40 mm without a collar decreased to 26 to 29 mm with cervical collar, and in a quarter of the subjects, mouth opening was reduced to 20 mm or less. A common pattern of practice is therefore to loosen or open the rigid collar (i.e., removing the anterior element) during laryngoscopy after the application of MILNS. In general, when MILNS is substituted for a rigid cervical collar, the direct laryngoscopic view should improve, with a quoted incidence of C-L Grade 3 or 4 views improved to between 20%^51,67–69 and 50%.^70–72 Thiboutot randomized elective surgical patients to standard “sniffing” position or MILNS for DL. In this series, the incidence of C-L Grade 3 or 4 view in the MILNS group exceeded 50% versus 5% for the unrestricted, sniffing position, and 50% of MILNS patients could not be intubated on the first attempt, compared to 5.7% without MILNS.⁷⁰ The consistent message from the literature is that MILNS application is associated with difficult DL; strategies to improve laryngeal view (e.g., use of indirect video laryngoscopy) and facilitate tracheal intubation during the application of MILNS have been reported and will be discussed subsequently.

Why Is Traction No Longer Used During MILNS?

Older publications make reference to using in-line traction when C-spine precautions were indicated. However, traction forces applied during MILNS may endanger the spinal cord if there is a serious ligamentous injury. Lennarson et al.⁶² noted distraction at the site of a complete ligamentous injury when traction forces were applied for the purposes of spinal stabilization during DL. Similarly, Kaufman et al.⁷³ demonstrated that in-line traction applied during radiographic evaluation resulted in spinal column lengthening and distraction at the site of injury in four recently deceased patients with ligamentous disruptions. Bivins et al.⁷⁴ also studied the effect of in-line traction during orotracheal intubation in four victims of blunt traumatic arrest who had unstable spinal injuries. Traction applied to reduce subluxation at the site of injury resulted in both distraction and posterior displacement at the fracture site. Current recommendations promote the use of in-line stabilization and not traction during airway interventions requiring C-spine precautions.

Does the Choice of Direct Laryngoscope Blade Impact the Degree of C-Spine Movement During Laryngoscopy?

Several investigators have studied C-spine movement caused by different DL blades. Two studies in elective surgical patients found significantly less (by about three degrees) head extension with Miller, as compared with Macintosh blade laryngoscopy.^46,75 However, other studies have failed to demonstrate a difference in motion between the two blades.^55,61,76 Studies with the levering tip McCoy/CLM-type blades have also generated conflicting results: some have found significantly less C-spine movement with use of the activated blade when compared to a Macintosh^52,77 while others have not.^63,78

In cadaver injury models, one study showed that Miller blade laryngoscopy resulted in significantly less axial distraction (1–2 mm) at the level of a surgically created C5–C6 transection than the Macintosh, but no difference in angular rotation or A-P displacement.⁶³ However, Aprahamian et al.’s⁵⁷ study of a single cadaver, also with an unstable C5–C6 injury, reported no difference between Macintosh and Miller blades. At present, there is no evidence that Miller blade use is preferred to the Macintosh for DL when attempting to minimize movement of the C-spine.⁷⁹

Is Any DL Blade Superior for Exposing the Glottis with Applied MILNS?

To date, there is no convincing evidence that either curved or straight blades are superior to the other for exposing the laryngeal inlet during DL with applied MILNS. However, a number of studies suggest that laryngoscopy using the levering tip McCoy/CLM blade with the tip activated may be helpful when a poor view is obtained in the setting of MILNS. Three studies of the McCoy blade report improvement of a C-L Grade 3 view to 2 or better in 83% (with applied MILNS)⁸⁰; 86% (MILNS with cricoid pressure)⁸¹; and 92% (rigid cervical collar) of cases respectively,⁸² compared with Macintosh blade DL.

How Do Alternatives to DL Such as Indirect Video-Laryngoscopes Impact C-Spine Movement During Tracheal Intubation?

Many of the alternatives to DL, such as indirect optical- or video-laryngoscopes appear to cause somewhat less movement of the C-spine during tracheal intubation. Laryngoscopy and intubation with the Bullard laryngoscope has been shown to result in significantly less C-spine movement than DL with Macintosh^41,76,83 or Miller blades.⁷⁶ Similarly, intubation with the Pentax Airway Scope (AWS) results in significantly less upper C-spine movement than DL with both attempted full^48,84 and minimal view⁸⁵ exposure of the cords. C-spine movement during AWS use is further reduced with passage of a tracheal tube introducer (TTI) via the blade’s delivery channel prior to ETT advancement.⁸⁶ Compared with the Macintosh blade, Airtraq-facilitated intubation appears to cause significantly less movement at some, but not all^43,45 of the studied C-spine motion segments. However, a more recent cadaver study using a surgically created unstable odontoid fracture failed to demonstrate a significant difference in space available for the spinal cord at the C1–C2 segment between Airtraq, Macintosh, and McCoy blade laryngoscopy and intubation. In this study, the DL blades were used to only expose a minimum (arytenoids) view, MILNS was applied, and a TTI was passed prior to the ETT.⁸⁷

The use of a GlideScope video-laryngoscope (GVL) during MILNS resulted in some reduction in mid-cervical (C2–C5) spine movement compared with DL in one study⁴⁴; another failed to show a significant difference in average spine movement at any level to that occurring during DL.⁵¹ Studies with the Bonfils and Shikani optical stylets have concluded that less C-spine movement occurred with the optical stylets compared to Macintosh blade DL.^44,83,88 Results with the LMA-Fastrach vary, with some studies showing small amounts of flexion of the upper C-spine during ILMA insertion and subsequent intubation with MILNS,⁸⁹ while others have demonstrated extension, although not significantly different from that encountered during DL.⁹⁰ Tracheal intubation using a flexible bronchoscope (FB) results in less movement of the head and neck compared to DL,⁹⁰ GVL,⁹¹ and LMA-Fastrach⁵⁸-faciliated intubation in anesthetized patients. However, this information must be tempered with the appreciation that FBs are expensive, more difficult to use, particularly in the presence of blood and secretions, and can be time-consuming in emergencies.⁴⁰ FBs are generally used if an awake intubation is elected, an option that permits the advantage of post-intubation neurologic reassessment.

To summarize, although studies have suggested that many of the foregoing devices result in less movement at some C-spine segments than DL, there is no evidence of a better neurological outcome with their use in the patient at risk with a C-spine injury. Indeed, as discussed in the next section, use of such alternatives to DL is probably most beneficial to maximize the chances of laryngeal visualization and first-attempt intubation success with MILNS application during tracheal intubation.

How Do Adjuncts and Alternatives to DL Such as Indirect Video-Laryngoscopes Compare for Successful Intubation of the Patient Undergoing MILNS?

The TTI is a valuable adjunct to DL in the patient undergoing MILNS. Nolan and Wilson⁶⁸ randomized half of 157 patients undergoing MILNS in the operating room to attempted primary passage of the tube, or prior passage of a TTI. Although the primary technique was quicker on average, 11 patients in this group required >45 seconds for intubation, and there were five failures. All five failures were successfully intubated with adjunctive use of the TTI. There were no failures in the TTI group.

Studies of the Bullard laryngoscope,^41,65,92 GVL,^69,92,93 CMAC video-laryngoscope with use of the Macintosh blade,⁹⁴ McGrath Series 5 video-laryngoscope,⁹⁵ Pentax AWS,^69,96–98 and Airtraq,^99–102 or optical stylets^71,103 have documented one or more of a significantly improved laryngeal visualization,^{69,70,100,101} better success rate,^72,101,104 or lower intubation difficulty score (IDS)^{70,100,101,103,105} compared to Macintosh blade DL in patient or cadaver studies during MILNS or use of a cervical collar. A study that compared the Pentax AWS with the GlideScope in a series of adult patients with MILNS reported more rapid intubation with the AWS.¹⁰⁶ One pediatric study comparing the GlideScope to DL (curved and straight blades were used) failed to demonstrate an improved view during MILNS.¹⁰⁷

Several series evaluating LMA-Fastrach use in patients with applied rigid collars have reported intubation success rates comparable to those obtained in unrestrained elective surgical patients^108,109: the one study reporting a poor success rate under these conditions had included cricoid pressure in the study protocol.¹¹⁰

In general, most of the alternatives to DL, including video-laryngoscopes used in the patient undergoing MILNS cause comparable or less neck movement and generally enable easier visualization and/or tracheal intubation. For those with access to the devices and skill in their use, they may be a good option for such conditions, although compared to DL there are no data indicating an outcome benefit.

Is Cricoid Pressure Contraindicated in Patients with Potential C-Spine Injury?

The reader is referred to Chapter 5 for a more detailed discussion on the risks and benefits of cricoid pressure in emergency airway management. The authors’ opinion is that cricoid pressure may prevent aspiration in some patients, has low potential to do harm, and can readily be removed if its application results in difficulty in airway management; it generally may be applied when there is a concern that the risk of regurgitation and aspiration is increased. With specific reference to the use of cricoid pressure in the patient with potential C-spine injury, radiographic studies (albeit in cadaveric specimens) have generally found that C-spine movement with application of cricoid pressure is within physiologic limits. In one study of six cadavers with intact C-spines, with 40N of applied cricoid pressure and using radiographs for assessment, Helliwell et al.¹¹¹ found a median A-P displacement of <1 mm. In an earlier study of cadavers with a surgically created unstable C-spine at the C5–C6 level, Donaldson et al.⁵⁶ reported a mean of 0.64 mm of A-P translation, 3.6 degrees of angulation, and 1 mm of spinous process distraction with cricoid pressure application.

The decision to apply cricoid pressure in the patient with TBI must be considered in the context of both its potential for minor risk of C-spine movement and other detrimental effects. Cricoid pressure may interfere with FMV or efforts to place or ventilate through an EGD.¹¹² Difficulty with ventilation likely results from obstruction of the airway by the applied pressure; the loss of airway patency may also shorten the time to desaturation even in the absence of ventilation.¹¹³ A recent review has suggested that cricoid pressure may also adversely impact airway management with DL, the lightwand, and the FB.¹¹² Thus, although cricoid pressure appears to result in radiographic movement that is within physiologic limits,³⁶ it may be prudent to reconsider its use in patients with known unstable lesions at or near the level of the cricoid cartilage, or in those in whom difficulty with FMV or tracheal intubation has been encountered.

Does Administration of an Induction Agent and/or a Muscle Relaxant by Itself Have Any Effect on the C-Spine?

Historically, concern has been raised that administration of an induction agent and muscle relaxant to the patient with a C-spine injury could release any “splinting” of an unstable segment by adjacent muscle spasm. However, there is no published evidence for a clinically significant increase in the degree of cervical spinal movement due solely to induction agent and muscle relaxant administration.

Do EGDs Cause Significant C-Spine Movement on Insertion?

In a cadaver study, both the LMA-Classic and LMA-Fastrach were found to transiently exert pressure on the upper cervical vertebrae during insertion, suggesting the potential to cause some degree of flexion in that location.¹¹⁴ This was confirmed in a later in vivo study in which the LMA-Fastrach was found to cause an average of 1.4 to 3.0 degrees of flexion of the upper C-spine during insertion and a lesser amount upon removal.⁸⁹ This contrasts with the extension caused by direct and video-laryngoscopy. In a cadaver model of a destabilized C3 segment, both the LMA-Fastrach and LMA-Classic caused posterior displacement of the unstable segment, yet significantly less than that caused by Combitube™ insertion.⁵⁸ However, in all cases the movement was less than that deemed “physiologic” (see section “What Range of Cervical Spine Movement Is Considered Within Physiologic Limits?” in this chapter). Furthermore, EGDs are vital rescue oxygenation tools in difficult airway situations, with their benefits in reoxygenating a hypoxemic patient often outweighing any potential risk posed by small movements of the C-spine, particularly if care is taken to minimize such movement.

How Does a Cervical Collar or MILNS Influence the Ease of Insertion of, or Ventilation Through EGDs? What About Tracheal Intubation Through EGDs?

Clinical trials, many using a cross-over design have indicated that presence of a cervical collar or application of MILNS without a collar adversely impacts overall or first-attempt success insertion rates with the LMA-Classic,¹¹⁵ LMA-Fastrach,¹⁰⁴ Laryngeal Tube,¹¹⁶ and Combitube.¹¹⁷ Comparative studies have indicated a slight advantage to the LMA-Proseal¹¹⁸ and the LMA-Fastrach¹¹⁹ when compared with the LMA-Classic under these conditions, and substantially better performance of the LMA-Fastrach when compared to the Laryngeal Tube.¹²⁰ Interestingly, in a study of the LMA-Supreme, once inserted, application of a cervical collar increased the effectiveness of seal pressure from a median of 22 to 27 cm H₂O.¹²¹

A small case series of 10 patients published in 2000 suggested a poor success rate with blind intubation through the LMA-Fastrach while wearing a neck collar with applied cricoid pressure.¹¹⁰ However, larger series published subsequently have reported that intubation success rates with blind^104,122 or FB facilitated¹²³ intubation through the LMA-Fastrach during cervical collar or MILNS application appear to be similar to standard conditions.

What Effect Does Cricothyrotomy Have on C-Spine Movement?

Surgical cricothyrotomy was originally advocated as a preferred airway intervention in patients at risk for C-spine injury, rather than orotracheal intubation, and is now deemed to be an appropriate alternative in an urgent situation if oral or nasal routes cannot be used or are unsuccessful. Although long considered safe in the presence of a C-spine injury, the effect on C-spine movement of surgical cricothyrotomy has not been extensively studied. Gerling et al.¹²⁴ studied C-spine movement during open surgical cricothyrotomy in a series of 13 cadavers with a complete C5–C6 transection. A-P displacement was limited to 6.3% of C5 body width (i.e., 1–2 mm of subluxation), and axial distraction to <1 mm across the C5–C6 injury during the procedure. Earlier, using a similar injury model in a single cadaver, Donaldson et al.⁵⁶ reported that A-P displacement was limited to 0.9 mm during tracheotomy. As these movements are within physiological levels, values from both studies would likely be less than the threshold for clinical significance.

How Safe Is It to Intubate the Trachea of the Patient with a Potential C-Spine Injury?

There is no evidence that tracheal intubation using careful direct or video-laryngoscopy with in-line stabilization results in secondary neurologic injury in patients with unstable C-spine fractures.^125–128 Traditionally, oral intubation using DL was deemed dangerous because it was thought to cause excessive spinal movement with the potential for secondary injury.⁶⁷ It was thought that such secondary injury could be avoided by the careful performance of nasotracheal intubation or cricothyrotomy. Although there were no data at that time to support this thesis and later data would seem largely to refute it, this hypothesis had achieved a sufficiently widespread acceptance as to be labeled a “therapeutic legend of emergency medicine” by Rosen.¹²⁹ McLeod and Calder reviewed the use of the direct laryngoscope in patients with spinal injury or pathology.¹³⁰ With the possible exception of one case,¹³¹ they concluded after review and analysis of the case reports that it was unlikely that the use of the direct laryngoscope was the cause of the myelopathies reported. As well, a report analyzing cases in the American Society of Anesthesiologists’ Closed Claim database echoed the view that most case reports ascribing cord injury to intubation in patients with unstable injury failed to provide sufficient data to support firm conclusions regarding causation.¹²⁸ In that analysis, 47 cases of cervical injury claims were identified in the database of 7740 claims filed between 1970 and the end of 2007. In one instance, airway management was judged to be a probable contributor to cord injury in a C-spine surgery patient; in another it was judged to be a probable contributor to injury in a patient who presented with an unstable injury but who did not have surgery. In both instances, the patients underwent difficult DL without cervical stabilization. The potential for aggressive DL with unrestricted spinal movement to cause neurological injury in spine-injured patients has also been detailed in two other reports.^131,132 However, the message that these reports emphasize is the need for spine stabilization in patients at risk of a C-spine injury until such injury is ruled out or definitive therapy for diagnosed C-spine injury is implemented, and not that careful direct or video-laryngoscopy is contraindicated.

Is DL Acceptable for Intubation of the Patient with a C-Spine Injury?

There is clearly a difference of opinion in the literature regarding the optimal means of securing the airway by tracheal intubation in patients with C-spine injury. Many authors have reported on the use of the direct laryngoscope in the management of patients with C-spine injury for both elective and emergency intubations.^{125–127,133–138} Most of these studies are limited both by their small sample size and their retrospective nature. However, they do reveal that neurological deterioration in spine-injured patients is uncommon after airway management when appropriate care is provided, even in high-risk patients undergoing urgent tracheal intubation. Reassuring as they are, these studies are not sufficient to rule out the possibility that on rare occasions, and even when provided with the utmost care, airway management undertaken in insolation or as part of a more complex clinical intervention, may result in neurological injury.

The use of a direct laryngoscope following induction of anesthesia in the patient with a head injury is deemed an appropriate practice option by the American College of Surgeons as outlined in the manual of Advanced Trauma Life Support Program^® (ATLS^®, 2008) for doctors and by experts in trauma, anesthesia, and neurosurgery^{126,127,130,139–148} and by the Eastern Association for the Surgery of Trauma.¹⁴⁹ Advantages of the direct laryngoscope in this setting include its effectiveness, the ability to visualize and remove upper airway foreign bodies during use and clinician familiarity. These advantages have the potential to be augmented by the contemporary direct-style video-laryngoscopes—that is, those with Macintosh-shaped blades. Furthermore, indirect-type video-laryngoscopy blades may enable visualization of the larynx with less extension of the upper C-spine and will facilitate visualization during MILNS. Enthusiasm has been expressed by neuroanesthesia experts for the exclusive use of the FB to facilitate tracheal intubation in patients with a C-spine injury, citing this as the optimal practice option.¹⁵⁰ However, it is worth noting that over 40% of American anesthesiologists admit that they are not comfortable using an FB for airway management.¹⁵¹ Further, it should be recognized that significant difficulties may be experienced during the use of the bronchoscope, even by persons skilled in its use, during airway management in patients with a C-spine injury.¹⁵² Carefully performed direct or video-laryngoscopy with appropriate MILNS in the trauma patient at risk for a C-spine injury can be considered a pattern of practice within the standard of care.

Is There Anything Else That Might Make Airway Management More Difficult in the Patient with a C-Spine Injury?

A small number of case reports and case series document the association of pre-vertebral retropharyngeal hematomas with some injuries of the upper C-spine, particularly with a hyperextension injury that disrupts the anterior elements of the spinal column.^60,153–157 Such patients may present with symptoms of dysphagia and dyspnea, with the potential for difficult laryngoscopy due to anterior displacement of the laryngeal inlet. As well, patients with chronic spinal disorders, especially those resulting in abnormal ossification (e.g., ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis) may present with spine injury, including after relatively trivial trauma. Increased difficulties with tracheal intubation and high rates of medical and surgical complications resulting from care have been reported in such patient populations.^158,159

What Are the Post-Intubation Considerations in the Head-Injured Patient?

Objective confirmation (e.g., with an end-tidal CO₂ monitor) of correct tracheal placement of the ETT is essential. Recognizing the importance of maintaining CPP, blood pressure should be reassessed after airway interventions and any unacceptable drop corrected with fluid and/or vasopressors. Pupils should be reassessed. After checking for optimal depth, the ETT should be firmly fixed to the patient, as many transfers will occur (e.g., to the diagnostic imaging department and thereafter to the ICU or operating room). However, tight ties encircling the neck should be avoided. If the patient’s blood pressure permits, a slight head-up position can be achieved by placing the stretcher in the reverse Trendelenburg position. This will promote venous drainage and may help reduce elevated ICP, if suspected.