Authors' Reply to Letter to the Editor "Comparing Sedation Regimens for Awake Fiberoptic Intubation".

We appreciate Prof. Xue et al. for their thoughtful comments on our study.[1] We agree with them that history of smoking and respiratory comorbidities can increase airway reactivity to airway irritation, resulting in an increased severity of cough. In our study, patients with a history of smoking and respiratory comorbidities were excluded and the demographic data of patients were comparable between the groups.

Furthermore, two senior anesthetists actualizing our study had equal proficiency with the use of fiberoscope and had performed more than 50 fiberoptic intubation for difficult airway management before this study. To ensure the consistency and repeatability of measurements, the procedure of awake fiberoptic nasotracheal intubation was normalized by video training and the test tools were illustrated for all participants before the study. In addition, we know that both patient's head position and airway clearance procedure can affect ease of fiberoscopy and tracheal tube placement. In our study, the patient's head was placed in the sniffing position with a 6 cm-high firm pillow under the occiput and the jaw-thrust was performed for the airway clearance.

As to the airway topical anesthesia, we completely agree with Xue et al. that a reasonable waiting period after each lidocaine spray helps ensure topical anesthetic to go into effect and reach peak effect, but spray of lidocaine via the working channel of fiberoscope often does not cover the whole supraglottic and glottic areas, and maybe only covers a small airway area. Therefore, even the contact time of lidocaine with the airway mucosa is enough, it may also not meet the requirement to pass fiberoscope and tracheal tube, as shown in the previous studies.[23] In the previous study by Xue et al.,[2] 61.5–73.1% of patients displayed grimacing and coughing responses during awake fiberoptic orotracheal intubation, though the patients received the classic “spray-as-you-go” technique under midazolam and fentanyl sedation. Jiang et al.[3] also showed that the incidence of coughing was 43.3% in patients receiving the glottis topical anesthesia with pressure-driven 2% lidocaine spray 3 times for 20 s each time at a 30-s interval. Despite a short interval of lidocaine spray used in our study did not ensure topical anesthesia to reach peak effect, grimacing, and coughing mainly occurred during advancement of fiberoscope and tracheal tube into the trachea, and most patients only exhibited slight grimacing and coughing, which met the requirements of comfort and adequate cooperation for awake fiberoptic intubation (AFOI).

We are very sorry not to define clearly intubation score, a multiple-factor variable including the ease of AFOI, scores of patient reaction and coughing during AFOI.[2] In our study, power analysis of sample size was actually performed according to patients’ reaction scores, rather than intubation score.

Finally, in available literature, a loading dose of dexmedetomidine ranging from 0.4 to 1.5 μg/kg has been used for sedation combined with or without midazolam for AFOI. However, there is not information regarding hypnotic synergism of dexmedetomidine and midazolam when using them together. A possibility shown by Cattano et al.,[4] a given dose of dexmedetomidine 0.4 μg/kg combined a dose of midazolam 2 mg did not produce sufficiently sedation. In our experience, dexmedetomidine 1 μg/kg combined with midazolam 2 mg can cause deep sedation, which may place patients at a risk of airway uncontrol. Moreover, we completely agree with Xue et al. that prolonged preparation time for targeted sedation level may challenge a patient's patience and comfort. Unfortunately, the time required for targeted sedation level was not measured in our study. This is a limitation of our study design.