We thank Drs. Todd and Bayman, Levine and Leibowitz, and Xue, Cheng, and Li for their interest in our article “Awake fiberoptic or awake video laryngoscopic tracheal intubation in patients with anticipated difficult airway management.”1 We value their questions and considerations.
Drs. Todd and Bayman raise an important issue concerning postrandomization exclusion and missing intention-to-treat analysis. We agree that postrandomization exclusion is a limitation of our study and an intention-to-treat analysis is preferable. We have now performed intention-to-treat analyses for both tracheal intubation time and the success rate for first attempt of intubation. In six of the seven cases with impossible transtracheal injection, patients’ airways were topically anesthetized and the data are available, and for patients without this information, we did the calculation under the assumption that the missing value was either the highest or the lowest recorded value.
By assigning the shortest intubation time (20 s), the median tracheal intubation time was 79 s using fiberoptic technique and 62 s with video laryngoscopic technique (P = 0.33). By assigning the longest intubation time (678 s), the median values are 80 and 72 s, respectively (P = 0.75). The success rate for tracheal intubation at first attempt was 80.4 and 69.4% for fiberoptic and video laryngoscopic techniques, respectively (P = 0.22), when the lowest number of attempts (1) was used. With the highest number of attempts (3) used for missing data, the corresponding rate at first attempt was 78.3 and 63.3% (P = 0.11). Therefore, these intention-to-treat analyses do not change the results substantially, and the conclusion is still the same.
Drs. Levine and Leibowitz are concerned that fiberoptic intubation is a threatened skill to learn and master. We do not advocate for abandoning fiberoptic intubation but merely examine an alternative intubation instrument that may be valuable for patients and anesthesiologists in difficult airway situations. Fiberoptic intubation is neither 100% safe for patients nor 100% reliable securing intubation in all patients with difficult airway. Therefore, alternatives are necessary, and we must constantly seek for the optimal intubation device that can be used for all patients with a safe and reliable result. Five patients in the McGrath VL group were excluded in accordance with our exclusion criteria to secure uniform airway analgesia for all included patients. However, to conclude that these patients could not undergo awake intubation is too excessive because awake intubation using other forms of topical anesthesia was not the topic of our study.
A mouth opening of at least 15 mm is necessary for introducing the McGrath video laryngoscope but is in fact less than that required for introducing the Macintosh and Miller laryngoscope. In addition, the video laryngoscopes improve the Cormack and Lehane grade one to two grades compared with the Macintosh and Miller laryngoscope. Therefore, we do not speculate that the Macintosh and Miller laryngoscope would have outperformed the McGrath video laryngoscope in our patient population. We did not want to inject directly into a tumor underneath the cricothyroid membrane, but to broaden this to state that we excluded all patients with neck pathology is an exaggeration. Patients, where transtracheal injection of local anesthetic failed, had at the time of inclusion been preanesthetically evaluated, and it was here judged possible to identify the cricothyroid membrane. In the future, ultrasound will possibly be helpful for correctly identifying the membrane in these patients where palpation fails.
Drs. Xue, Cheng, and Li state, “When adequate airway topical anesthesia is obtained, subsequent intubation is usually easy.” In the future, we would welcome a randomized, sufficiently powered study of topical anesthesia using video laryngoscopes versus fiberscopes, including an extended assessment of the performance of airway topical anesthesia. Surely, different techniques for local anesthetizing the airway all have advantages and disadvantages. The “spray as you go” technique may be unnerving to the less trained anesthesiologist because it causes coughing and perhaps a subsequent loss of vision when spraying through the fiberscope. Therefore, topical anesthesia may be achieved with the fiberscope but intubation may fail! We chose the transtracheal local anesthetic technique because of this procedure being the preferred method in the centers included in our study and because transtracheal anesthesia produces the least coughing during endoscopy.2 However, mastering different topical anesthesia methods will most certainly prove helpful in handling patients with difficult airways.
Finally, we think that Drs. Xue, Cheng, and Li would agree with us in the theoretical concern that video laryngoscopes may cause more pressure on the pharyngeal/laryngeal structures than the fiberscope. In this context, manikin studies have limitations because of the anatomy of manikins not being directly transferrable to patients. Airway manikins upper airway “tissue are stiff, noncompliant and static rather than soft, fragile, and dynamic.”3 For further elucidating this topic, we look forward to see the results of human studies.