Many techniques have been used for tracheal intubation of patients with known or suspected cervical spine disease . Some authors recommend a flexible fiberoptic bronchoscope (FOB) for initial intubation of these patients , and report a success rate near 100% . Others emphasize limitations of the FOB, noting that it is technically difficult to use and that it breaks easily . In one study, FOB intubation in an emergency room was successful only 72% of the time .
The Bullard laryngoscope (BL) also has been used for endotracheal intubation in cases of cervical spine instability. We recently treated a 13-yr-old child with Klippel-Feil syndrome (a segmentation-fusion anomaly of C1-2), congenital odontoid subluxation, and marked stenosis of the cervicomedullary junction, undergoing odontoid resection and halo application. This child's trachea was easily and rapidly intubated with the BL after failed attempts by experienced operators using the FOB, and one failed attempt at direct laryngoscopy with cervical immobilization . We, therefore, designed a study to directly compare the FOB and the BL with respect to rapidity of glottic visualization and intubation, and anatomic features predicting difficult intubation in patients requiring cervical immobility during endotracheal intubation.
This study was approved by our institutional review board, and written, informed consent was obtained from each patient. Seventeen adult patients, ASA physical status I, II, or III, scheduled for neurosurgical correction of a cervical spine problem, were included. Each patient was considered at risk for neurologic injury during endotracheal intubation based on a request for awake fiberoptic endotracheal intubation by the neurosurgical team, or radicular symptoms initiated or exacerbated by neck extension. Most showed evidence of spinal canal impingement on a preoperative magnetic resonance imaging scan. Patients were allocated randomly to one of two study groups for endotracheal intubation with the BL (Group BL; n = 8) or the FOB (Olympus BF Type P30; Olympus, Lake Success, NY; Group FOB; n = 9); before intubation, glottic visualization was performed using the alternative technique.
The following data were collected for each patient: height, weight, thyromental distance (measured with the patient supine and the neck in neutral position), and Mallampati class without phonation . Thyromental distance and Mallampati class were measured and recorded by one of us (AIC). (Height and weight were measured and recorded by an anesthesiology resident during routine preoperative assessment.)
Each patient was sedated using a combination of fentanyl, midazolam, and droperidol. Topical anesthesia of the airway was achieved with lidocaine ointment as previously described . Patients randomized to the FOB group first underwent laryngoscopy with the BL to visualize the glottis and vice versa. Time for glottic visualization was measured as the time from initial introduction of the laryngoscopy instrument through the lips until visualization of the glottic opening. After removing the scope from the airway, times for glottic visualization and intubation were recorded. After visualization of the glottis, but before intubation, 5 mL of 4% lidocaine was injected through the glottis using the instrument's medication port. All intubations were performed orally. Figure 1 shows a schematic representation of the experimental protocol.
All visualizations and intubations were performed by attending anesthesiologists or experienced senior residents, and each operator had to have successfully completed 10 prior intubations with the modality used. All intubations were performed with the neck in a comfortable position for the patient and with any preexisting immobilization device (e.g., collar, traction) in place. Nerve blocks and transtracheal lidocaine injection were not used before intubation.
Means +/- SD for intubation times were calculated for the BL and FOB groups and compared using Student's t-test for independent samples. Means +/- SD for glottic visualization times were also calculated for the BL and FOB groups and compared using Student's t-test for correlated samples. A correlation matrix was calculated by linear regression using glottic visualization time (for BL and FOB) and the anatomic variables, including weight, height, body mass index, thyromental distance, and Mallampati class. P < 0.05 was considered significant for each regression analysis and t-test.
Glottic visualization was uniformly successful on the first attempt in both groups. Endotracheal intubation was also uniformly successful, although one intubation in the FOB group took 183 s because of difficulty passing the endotracheal tube through the glottis after an easy laryngoscopy. No new neurologic deficits were observed after endotracheal intubation.
Times for glottic visualization and endotracheal intubation are summarized in Table 1 and Table 2, respectively. Both glottic visualization and intubation were achieved significantly more rapidly in the BL group than the FOB group.
A matrix examining intercorrelations of the study variables is shown in Table 3. Significant correlations were not observed between body mass index or Mallampati class and time for glottic visualization with either the BL or the FOB. A significant negative correlation was found between thyromental distance and glottic visualization time using the BL Figure 2. No significant correlation between thyromental distance and glottic visualization time was observed for the FOB.
There are many endotracheal intubation techniques commonly used for patients with known or suspected cervical spine injury. Despite two case reports of quadriplegia after endotracheal intubation in patients with unrecognized cervical spine injuries [8,9], there is no basis for stating that a particular technique is either safe or dangerous .
The BL may be an alternative to the FOB for endotracheal intubation with minimal cervical spine movement. A recent study of patients with normal cervical spines reported head extension of only 2 degrees during endotracheal intubation with the Bullard versus 10 degrees for the Macintosh and 11 degrees for the Miller blade . Significant reductions in radiographic cervical spine extensions were found for the Bullard versus the Macintosh blade at the atlantooccipital joint, atlantoaxial joint, and C3-4. Median atlantooccipital extension angles were 50% smaller with the Bullard versus the Macintosh laryngoscope.
The BL compared quite favorably with the FOB, yielding faster glottic visualization and endotracheal intubation. That thyromental distance is negatively correlated with glottic visualization time when using the BL may imply that it is less suitable for patients with unstable necks and coexisting micrognathia. Although use of the BL has been advocated in micrognathia , it is unclear whether extreme micrognathia combined with cervical spine immobility may predict actual failure with the BL, as the time for longest glottic visualization with the BL was 23 s in our study, and this was less than the mean time for visualization using the FOB.
The BL has significant advantages over the FOB. It is more portable, less easily damaged, and less expensive to repair than the FOB. Consequently, if the BL can replace the FOB in certain patient populations, cost savings may accrue.
That intubation using the BL is 53 s faster than when using the FOB may seem clinically insignificant. Indeed, when intubating a very well-sedated patient at no risk for regurgitation under ample topical airway anesthesia, a faster intubation may not confer significant clinical advantage. However, awake sedation does not necessarily protect the patient from recall, and that the patient is awake does not necessarily imply that ventilation will be adequate and the airway protected from pulmonary aspiration of gastric contents. Where a patient is anxious, or the airway is poorly topicalized, a reduction in airway instrumentation time may be beneficial. Conversely, when a patient is hypoventilating or at risk for aspiration, a 50% reduction in the time window, during which an adverse event can occur, may reduce the risk that there will be a complication.
In conclusion, awake endotracheal intubation in patients at risk for neurologic injury during intubation may be reliably accomplished with the BL more rapidly than with a FOB. The performance of the BL, however, appears to deteriorate in micrognathic patients with coexisting neck immobility.
The authors thank Faith McLellan, Joann Aaron, and Donald S. Prough, MD, for reviewing an early draft of this manuscript, and the residents and faculty of The University of Texas Medical Branch for participating in this study.
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© 1995 International Anesthesia Research Society
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