Optimal airway management strategies in patients with unstable cervical spines remain controversial and a challenge for anesthesia providers (1–3). Although direct laryngoscopy for endo-tracheal intubation is a reliable and familiar method of securing the airway (4,5), this procedure may lead to extension of the cervical spine even in patients with in-line stabilization (6–8). This may increase the risk of spinal cord injury in patients with cervical spine disorders (9). Because many anesthesia providers are reluctant to use conventional laryngoscopy in patients with potential cervical spine instability, alternative methods for securing the airway are advocated (7,10–12).
Fiberoptic laryngoscopy in awake patients may facilitate tracheal intubation with little or no cervical motion (13,14); this technique, however, has several inherent limitations including patient cooperation, specialized expertise, complication with excessive secretions, blood, or vomitus, and the high cost of equipment maintenance.
A newly designed lightwand device (Trachlight™, Laerdal Medical, Armonk, NY) or an intubating laryngeal mask (Fastrach™, Intavent Ltd, Berkshire, UK) may avoid hyperextension of the occipito-atlanto-axial complex. These new devices have been suggested as alternatives for safer tracheal intubation than conventional direct laryngoscopy (15–18). However, most studies of these devices have been performed in patients with normal airways, and there are few objective data that guide appropriate selection of either of them.
We therefore conducted a prospective randomized study to evaluate and compare the efficacy of these devices in patients with known or potential spine disorders.
After IRB approval, 160 patients, ASA physical status I–II were enrolled in this study. All patients were scheduled to undergo cervical spine surgery. Written informed consent was obtained from all subjects before participating in the study.
Before performing the study, a single investigator (YI) had used Fastrach™ in 33 patients and Trachlight™ in 37 patients with the neck maintained in a neutral position. We confirmed that there was no technical difficulty in the use of the devices. The investigator had used a standard laryngeal mask airway for more than 10 yr in routine practice, whereas he had never used Fastrach™ or Trachlight™ before the preliminary trials.
The same investigator assessed the risk of induction of general anesthesia in all patients. If difficulty in mask ventilation with a neutral position of the head and neck was predicted after patient assessment, the patient was withdrawn from this study. In excluded cases, awake nasal fiberoptic intubation was applied. The patients included in this study were randomly assigned into either a Trachlight™ group or a Fastrach™ group. In both groups, general anesthesia was induced with 1–2 mg/kg propofol and 100 μg fentanyl IV and muscle relaxation was produced with 0.1 mg/kg vecuronium IV. All procedures were performed with the patient’s head and neck placed in a neutral position using an appropriately sized pillow. The neck collar was removed because it would prevent mask ventilation and light identification on the neck; whereas in the patient with a halo-vest, we attempted the trials without removing the vest. We used a reinforced tracheal tube (Fuji System, Tokyo, Japan) in the Trachlight™ group and a BlueLine™ tube (Portex, Hythe Kent, UK) in the Fastrach™ group. In both groups, an appropriate size of the tracheal tube was selected (inner diameter, 7.5–8.0 mm in males and 7.0–7.5 mm in females).
In the Trachlight™ group, two attempts limited to 30 s each were allowed for tracheal intubation. If it was impossible to intubate the trachea within these two attempts, it was regarded as a failure and the study was terminated. The trachea was then intubated with the investigator’s preference.
In the Fastrach™ group, a size #5 Fastrach™ was used unless it was judged to be too large; in such a case, a size #4 was chosen. Two attempts for insertion of the laryngeal mask portion of the Fastrach™ system were allowed. After the insertion, the cuff was inflated with 25–40 mL volume of air. Balloon pressure was manually verified. A respiratory system was connected and then manual ventilation was attempted. When tidal volumes with more than 10 mL/kg and an appropriate movement of the chest wall were obtained during manual ventilation with 15 cm H2O airway pressure, it was judged a clinically acceptable ventilation. The respiratory system was disconnected and then insertion of an endotracheal tube through the Fastrach™ was attempted. Only one attempt was allowed for “blind” tracheal intubation, because we felt that manipulation of the Fastrach™ may influence alignment of the cervical spine. If the blind intubation failed, fiberoptic bronchoscope-guided tracheal intubation through the Fastrach™ was attempted. If it was impossible to insert Fastrach™, or impossible to intubate the trachea with both attempts, it was regarded as a failure and the study was terminated. The trachea was then intubated with the investigator’s preference.
The number of attempts and the time for tracheal intubation, defined as the duration between the time when the attempt for insertion of the test device into the oropharynx was started and the time when manual ventilation through the tracheal tube was restarted, were recorded. Any complications during the attempts were recorded. Postoperative assessment by patient interview and review of the chart for neurological examination were performed on postoperative day 7. Demographic data and intubation time were reported as mean ± sd. All continuous data of the Trachlight™ group and the Fastrach™ group were analyzed using an unpaired Student’s t-test. Nominal data were analyzed using the χ2 contingency table. To examine if there was any skill acquisition during the study period, it was divided into four epochs and the data of the success rate, and the intubation time were compared between the epochs using the Kruskal-Wallis test and one-factor analysis of variance, respectively. P < 0.05 was considered statistically significant.
Preoperative diagnoses in 160 patients are shown in Table 1. One-hundred-forty-eight patients (74 patients each) were enrolled in analysis in this study. There were no significant differences between groups in gender, age, height, or weight (Table 2). An additional 12 patients, in whom difficult mask ventilation was suspected, were withdrawn from the study. In these patients all intubations were successfully accomplished under awake nasal fiberoptic laryngoscopy. In 74 patients in the Trachlight™ group, intubation was successful at the first attempt in 67 (90.5%) cases and at the second attempt in 5 (6.8%) cases. The overall success rate for tracheal intubation was 97.3% (72 of 74 patients). In contrast, in 74 patients in the Fastrach™ group, ventilation through the Fastrach™ was acceptable within two attempts for insertion in 59 (79.8%) cases, and blind tracheal intubation through the device was possible in only 42 (56.8%) cases with first attempt. In 17 patients in whom ventilation was acceptable but blind tracheal intubation through the Fastrach™ was impossible, fiberscope-guided tracheal intubation was successful in 12 (70.6%) cases. The overall success rate was therefore 54 of 74 patients (73.0%) in the Fastrach™ group (Fig. 1).
Mean intubation time, for cases in which intubation was successful at first attempt, was significantly shorter in the Trachlight™ group than in the Fastrach™ group (23 ± 9 s versus 71 ± 24 s) (Fig. 2). There were no significant differences in the results for the four epochs during the study period (Fig. 1,2).
In the Trachlight™ group, two failed cases were resolved with fiberoptic laryngoscopy. In 20 patients in whom tracheal intubation failed in the Fastrach™ group, 17 cases were resolved with Trachlight™, and the remaining 3 cases were resolved using fiberoptic bronchoscope without the use of Fastrach™. Consequently in all cases in which intubation failed with Fastrach™, the trachea was successfully intubated with the alternative devices.
During the intubation procedure, minor mucosal bleeding was recognized in 14 patients in the Fastrach™ group, compared with 2 cases in the Trachlight™ group. Minor nasal bleeding was seen in 3 of 12 requiring fiberoptic laryngoscopy cases. No other complications such as dental injuries or unexpected respiratory and circulatory changes occurred during the procedure.
On postoperative day 7, neurological deterioration as compared to the preoperative state was noted in 2 cases in the Trachlight™ group, 1 case in the Fastrach™ group, and 1 case with the awake fiberoptic technique. No patient complained of throat discomfort at this time in any group.
In this study we demonstrated that tracheal intubation without neck movement using Trachlight™ was more successful and required less time than Fastrach™. There was a 2.7% failure rate with Trachlight™, and 90.5% of intubations were successful at the first attempt, compared with 27.0% failure rate and 56.8% success rate with Fastrach™ without fiberoptic laryngoscopy. During the study period there was no skill acquisition of the devices used. This suggests that the skill itself did not influence the results. Therefore, Trachlight™ may be superior for orotracheal intubation with respect to reliability, rapidity, and safety compared with Fastrach™ in patients with cervical spine disorders.
Several previous reports have shown the usefulness of Fastrach™ in patients with cervical spine disorders (17–19); however, the studies were performed in simulated patients or were anecdotal reports, and there was no comparison with alternate devices. Successful tracheal intubation with Fastrach™ depends on neck position (20,21). However, movements of the head and neck are limited in patients with cervical abnormalities. We believe that the decreased success rate with Fastrach™ compared with the previous studies (22,23) is attributable to keeping a neutral position without neck movement.
In this study we chose a BlueLine™ tracheal tube for economical reasons in the Fastrach™ group. This may be another reason for the decreased success rate in the Fastrach™ group because the manufacturer recommends the use of a dedicated straight silicone tube for intubation through the Fastrach™ for the best results (15).
In contrast, Hung et al. (15) reported that difficulty in tracheal intubation using the Trachlight™ does not appear to be influenced by anatomical variations of the upper airway. There was no correlation between intubation time and airway variables such as mandibular protrusion, mento-hyoid distance or Mallampati class. We therefore believe that the Trachlight™ may be more reliable than the Fastrach™ in the patient whose head and neck are required to be in a neutral position.
Our intubation protocol allowed only two attempts, each within 30s in the Trachlight™ group. In the Fastrach™ group, only one attempt was allowed for blind intubation through Fastrach™ after the airway had been established within two attempts for insertion because we wanted to evaluate the reliability in the context of clinical simplicity and rapidity. This protocol seems more strict than those in previous studies regarding the usefulness of Fastrach™(22,23). However, our protocol may reflect actual clinical reliability of these devices.
The second choice of instruments was decided by the investigator when the intubation failed within the protocol. Most cases failed with Fastrach™ were resolved with Trachlight™ (17/20). In contrast, two cases of failure with Trachlight™ were resolved with fiberoptic laryngoscopy. These results also suggest that Trachlight™ has an advantage of reliability over Fastrach™ in such a time-limited situation.
Keller et al. (24) have reported that laryngeal mask devices exert greater pressures against the cervical vertebrae than does direct laryngoscopy. Kihara et al. (25) has reported that the intubating laryngeal mask can produce posterior displacement of the cervical spine. These data, plus our observation of less bleeding with the Trachlight™, suggest that tracheal intubation using Trachlight™ may be a more gentle technique than the Fastrach™ in the patient with a neutral position of the head and neck, although there are few data regarding precise cervical movement in the use of the Trachlight™.
In conclusion, we demonstrated that, for well trained personnel, the Trachlight™ may be superior to the Fastrach™ for orotracheal intubation in elective patients with cervical spine disorders, with respect to reliability, rapidity, and safety. Anesthesia providers responsible for securing the airway in patients with cervical spine disorders should be familiar with the Trachlight™ intubation technique.
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