Endotracheal intubation of patients with known or suspected cervical spine instability presents the challenge of securing the airway without causing or exacerbating neurologic injury. When laryngoscopy is selected over fiberoptic intubation, there is concern that there may be excessive cervical spine motion/displacement. In this case report, we describe the use of postintubation radiography to determine whether there was a change in cervical spine alignment after intubation in a patient with an acute traumatic Type III odontoid fracture.
The patient reviewed this case report and gave written permission for the authors to publish the report.
A 72-year-old female presented to the operating room at 21:15 for urgent irrigation, debridement, and external fixation of open comminuted fractures of the right tibia and fibula and a closed midshaft fracture of the right femur. Before her presentation, a review of the electronic medical record revealed she had been an unrestrained front passenger in a single vehicle accident with airbag deployment approximately 10 hours earlier. The patient had not been ejected from the vehicle and had not lost consciousness. Upon hospital admission, cervical spine computed tomography showed moderate to severe degenerative disc disease at C5-C6 and C6-C7, and a nondisplaced fracture of C2 involving the dens and C2 body, classified as a Type III dens fracture1 (Fig. 1). A subsequent cervical spine series obtained 2 hours before her arrival to the operating room showed normal alignment of all bony structures and evidence of moderate prevertebral swelling. Other preoperative studies revealed no other injuries. The patient’s medical history was significant for obesity (84 kg, body mass index = 33 kg/m2), hypertension, hyperlipidemia, hypothyroidism, and a hiatal hernia with uncontrolled gastroesophageal reflux. The patient reported she had a normal cardiac catheterization and echocardiogram during a prior chest pain evaluation. Her medications included alendronate, aspirin, atorvastatin, carvedilol, enalapril, furosemide, levothyroxine, meloxicam, nortriptyline, and ranitidine. The patient last had solid food and liquids at 8:00 AM on the day of the accident. Preoperative laboratory studies included a hemoglobin concentration of 10.5 g/dL, creatinine of 0.7 mg/dL, troponin-T of <0.03 ng/mL, and a venous lactate of 1.4 mEq/L. On the basis of the information available before the patient’s presentation to the operating room, the plan had been to perform an awake fiberoptic intubation, followed by confirmation of preserved neurologic function, followed by subsequent general anesthesia and surgery.
On presentation to the operating room, the patient was supine with a Miami J cervical spine collar (Össur, Reykjavik, Iceland) in place. She was alert, conversant, and moving all 4 extremities spontaneously. Before administration of any medication, the patient began to vomit, producing approximately 100 mL of dark brown liquid. Without moving her head or neck, the patient was log rolled to the lateral position and her oropharynx was suctioned. IV metoclopramide (10 mg) and ondansetron (4 mg) were administered and she was returned to the supine position. An airway evaluation revealed upper and lower dentures (which were then removed), and a Mallampati class IV airway. The remainder of her physical examination was unremarkable and consistent with the absence of other injuries.
Because of the patient’s history of gastroesophageal reflux, and the presence of active vomiting with a nonempty stomach, the airway management plan was changed to consist of a rapid sequence induction of anesthesia with use of manual inline stabilization (MILS) and cricoid pressure. Her preinduction vital signs were: arterial blood pressure 138/66 mm Hg, heart rate 127 beats/min, and room air saturation 100%. The patient was administered oxygen and the anterior portion of the cervical collar was removed.2 Before induction, MILS was established as described by Criswell et al.3 and cricoid pressure was applied. Anesthesia was induced with IV propofol (100 mg) and succinylcholine (100 mg) in rapid succession. Videolaryngoscopy with a C-MAC® D-Blade (Karl Storz Endoscopy-America Inc., El Segundo, CA) afforded full visualization of the glottis and a 7.0 cuffed endotracheal tube was easily and rapidly passed through the vocal cords without apparent motion of the patient’s head or neck. No gastric fluid was seen in the pharynx or larynx. Thereafter, the anterior portion of the cervical collar was reapplied and the endotracheal tube was secured. Immediately after intubation, a cross-table lateral cervical spine radiograph was obtained to assess cervical spine alignment. The radiograph showed both the odontoid and body of C2 had not changed in their alignment in comparison to the preoperative state (Fig. 2). An orogastric tube was placed and 200 mL of brown liquid was removed from the stomach. Anesthesia was maintained with isoflurane in 50% oxygen, with a later conversion to sevoflurane. The 2-hour procedure was uneventful from both surgical and anesthetic perspectives. Upon emergence from anesthesia, the patient’s trachea was extubated and she readily followed motor commands in all extremities in the operating room. The patient was transferred to the intensive care unit for further management.
In patients with cervical spine instability, there is a concern that laryngoscopy and endotracheal intubation may result in cervical spinal cord injury.2,4,5 Accordingly, when the cervical spine is unstable, awake fiberoptic intubation is often chosen6 because of (1) studies demonstrating minimal cervical spine motion with this technique7,8 and (2) the ability to perform postintubation neurologic testing. However, awake fiberoptic intubation requires sensory anesthesia of the upper pharynx, larynx, and subglottic trachea,9 deliberately eliminating protective airway reflexes so that introduction of the fiberscope and endotracheal tube will not result in coughing or gagging and attendant motion of the cervical spine. Ablation of protective airway reflexes potentially increases the risk of aspiration of gastric contents. Because this patient (1) had a prior diagnosis of uncontrolled gastroesophageal reflux disease and (2) was actively vomiting large volumes of gastric material, it was our judgment that topical anesthesia of the airway carried prohibitive risk. We elected to induce general anesthesia and perform a rapid sequence intubation using cricoid pressure and MILS.2,4,5 We elected to use a videolaryngoscope because (1) MILS has been shown to decrease glottic visualization with conventional line of sight laryngoscopy10 and (2) the C-MAC D-Blade has been shown to provide better glottic visualization than conventional line-of-sight laryngoscope in patients predicted to be difficult to intubate.11
MILS was introduced in clinical practice in the 1980s and is intended to decrease motion at unstable cervical segments during laryngoscopy.12 However, 3 cadaver studies have reported that MILS does not affect motion of unstable cervical segments during conventional direct laryngoscopy and intubation.13–15 Therefore, use of MILS during intubation does not guarantee that pathologic motion of the unstable segment cannot occur.
Because the C-MAC D-Blade does not require a line-of-sight, one might expect that less cervical spine extension would be required for intubation when compared with conventional direct laryngoscopy. However, at the present, cervical spine motion during intubation with C-MAC D-Blade has not been characterized. Such studies have been performed with other videolaryngoscopes and have shown considerable diversity. Cervical spine extension with use of a GlideScope does not differ from that occurring with a Macintosh, at least in the upper cervical segments.16–18 In contrast, extension with an AirwayScope is approximately 40% less than with a Macintosh in all cervical segments.19,20 Finally, overall (Oc-C5) extension with use of an Airtraq is approximately 30% than that with a Macintosh, but is not significantly less in upper (Oc-C1, C1-C2) segments.21,22 Therefore, not all videolaryngoscopes result in less cervical spine motion than conventional line-of-sight laryngoscopes and, of those that do, motion differences are segmentally specific. Therefore, use of a videolaryngoscope during intubation does not guarantee that motion at an unstable segment is necessarily less than that which would occur with a Macintosh.
A recent study in patients with stable cervical spines showed that cervical spine motion/force relationships were nonlinear and differed among laryngoscopes.22 In particular, although the amount of force applied with the Airtraq (10 N) was only 20% of the force applied by the Macintosh (50 N), overall (Oc-C5) cervical spine motion with the Airtraq was still 66% of the Macintosh value (19 degrees versus 29 degrees, respectively). Despite greatly differing forces with these 2 laryngoscopes, there was not a significant difference in Oc-C1 or C1-C2 extension between these 2 laryngoscopes. The authors concluded, “Anesthesiologists should not consider ‘low-force’ laryngoscopes to necessarily result in proportionately less cervical spine motion.” This conclusion calls into question the common tactic assumption that a “low-force” laryngoscope should necessarily result in less motion at an unstable cervical segment than a “high-force” laryngoscope. For example, Wendling et al.23 observed no significant difference in C1-C2 extension between the Macintosh and Airtraq in a cadaver C2 (odontoid) fracture model. Thus, at the present, neither MILS nor use of any type of videolaryngoscope can guarantee that pathologic motion of an unstable cervical segment will not take place during intubation.
By obtaining a postintubation lateral radiograph, one can immediately determine whether postintubation cervical spine alignment differs from that present preoperatively. Obviously, a postoperative radiograph cannot address cervical spine motion during the intubation itself. However, given that laryngoscopy and intubation are typically accomplished in less than 20–30 seconds, motion transients during intubation would be correspondingly brief. Two experimental studies show that cervical spinal cord tolerance to compressive injury is time dependent. Functional recovery from even marked cord compression is possible with brief (<1 minute) compression intervals,24,25 whereas the likelihood of functional recovery markedly decreases with sustained cord compression.26 Therefore, we speculate that, in the presence of an unstable cervical spine, transients of cervical spine motion during intubation may be less important than the postintubation cervical spine position that will be maintained during subsequent hours of surgery and postsurgical care. If, after intubation, intervertebral extension and subluxation at the unstable segment(s) are unchanged, the clinician has substantive assurance that there is no new (or exacerbated) cord stretch or cord compression. If, however, new hyperextension and/or subluxation are present on the postintubation radiograph: (1) a neurosurgical or orthopedic surgical consultant may be able to reestablish preoperative cervical spine alignment and/or (2) the patient can be awakened from anesthesia and a neurologic examination performed.
Our observation of no change in postintubation alignment in the presence of an acute odontoid fracture is compatible with 1 case report.27 Specifically, Ostermeier et al. reported that a computed tomography scan obtained 30 minutes after intubation in a patient with an acute Type II odontoid fracture showed minimal (2–3 mm) anterior displacement of the fractured odontoid in comparison to the preintubation radiograph. In fact, after intubation, the previously posteriorly displaced odontoid fragment was more normally aligned relative to the body of C2. In a different case report, Morell et al.28 described the use of continuous fluoroscopy to monitor motion of an unstable C1-C2 segment during intubation. In this latter case report, almost no C1-C2 subluxation was observed during or after intubation with axial traction, although C1-C2 intervertebral extension during intubation was not reported. We cite these 2 other case reports not to suggest that intubation in the presence of C1-C2 instability does not carry risk of pathologic cervical spine motion. Rather, we cite these other reports to show that others have also found radiography to be helpful in the assessment of cervical spine displacement associated with intubation in the presence of unstable cervical segments. We suggest clinicians consider intra- or postintubation radiography as an aid in the airway management of patients with cervical spine instability.
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