Flexible bronchoscope versus video-laryngoscope for nasotracheal intubation in patients with anticipated difficult airway under topical anesthesia and dexmedetomidine infusion: A randomized controlled trial





Abstract


Background


Managing difficult airways with restricted mouth opening remains a challenge. In this regard, flexible bronchoscopes (FB) are considered the gold standard, offering precise tube placement. However, they require expertise and can be time-consuming. Video-laryngoscopes (VLs), such as the CMAC D-blade, provide enhanced glottic visualization and may reduce intubation time. While VLs are gaining popularity, data comparing them with FBs in this setting are limited. This study evaluates whether the CMAC D-blade VL can reduce intubation time compared to FB while maintaining similar success rates.


Methods


In this randomized controlled trial, 100 adult patients scheduled for elective head and neck or oral and maxillofacial surgery with anticipated difficult airways were randomized to receive awake nasotracheal intubation using either an FB or CMAC D-blade VL. The primary outcome was intubation time. Secondary outcomes included first-attempt success rate, overall success rate, and satisfaction scores.


Results


Out of 100 patients, 97 patients completed the study (FB: n = 49, VL: n = 48). Median intubation time was significantly shorter in the VL group (62 [53–71] sec) compared to the FB group (118 [107–134] sec; p < 0.0001). Success rates and intubation scores were similar, but anesthesiologist and patient satisfaction scores were better in the FB group.


Conclusion


The CMAC D blade video-laryngoscope reduces intubation time while maintaining similar success rates compared to the flexible bronchoscope for awake nasotracheal intubation with limited mouth opening. Despite the time advantage, the flexible bronchoscope was preferred by anesthesiologists and patients had more comfort.


Highlights




  • •

    Flexible bronchoscope: Gold standard for difficult airways.


  • •

    CMAC D Blade provides superior stability for intubation.


  • •

    Local anesthesia with dexmedetomidine ensures patient comfort.


  • •

    CMAC D blade easier to use for operators with less experience.


  • •

    We found that CMAC D blade took less time for intubation.



1


Introduction


Video-laryngoscopes (VL) have transformed airway management by increasing the ease of intubation, decreasing the need for cervical movement, improving the view of the glottic opening, minimizing the laryngoscopy response, and demonstrating higher success rates in the hands of both novice and experienced providers [ , ]. VLs have gained widespread popularity, and most airway management guidelines now mandate that anesthesiologists become proficient in their use, particularly for difficult intubations [ , ].


A flexible bronchoscope (FB) remains the gold standard for awake intubation under local anesthesia and sedation in patients with anticipated difficult intubation due to its precision and reliability [ ]. However, the flexible bronchoscope has limitations, including the need for significant operator expertise and longer intubation times, which may contribute to procedural delays and patient discomfort. Video-laryngoscopes, on the other hand, have shown promise as an acceptable alternative for awake intubation under sedation in patients with difficult airways [ , ].


In a previous study, Kramer et al. demonstrated that the use of the C-MAC® D-blade video-laryngoscope for awake nasotracheal intubation under topical anesthesia and sedation reduced intubation time while maintaining a similar success rate compared to flexible bronchoscope [ ]. However, the study was limited in scope and did not specifically focus on patients with restricted mouth opening, a critical airway management challenge.


To address this gap, our study aimed to compare the C-MAC® D-blade video-laryngoscope with the flexible bronchoscope for awake nasotracheal intubation under topical anesthesia in patients with limited mouth opening (<2.5 cm), a common characteristic in those undergoing maxillofacial and otorhinolaryngology surgeries. We also utilized intravenous dexmedetomidine, titrated to Ramsay Sedation Scale (RSS) and Bispectral Index (BIS) values, to optimize sedation and ensure patient comfort [ ].


Our hypothesis was that the use of a video-laryngoscope would reduce the time to intubation by 50 % compared to the flexible bronchoscope without compromising safety or procedural efficacy. This research aims to contribute to the evolving field of airway management by providing evidence to refine clinical protocols and enhance patient outcomes in difficult intubation scenarios.


2


Methods


After approval by the institutional ethics committee of AIIMS New Delhi (IECPG 717/December 23, 2020, RT-24/January 27 2021, OT-05/August 25 2021, and registration in the clinical trial registry of India (CTRI) at https://ctri.nic.in/Clinicaltrials/pmaindet2.php?EncHid=NTAyNTU=&Enc=&userName= (CTRI number: CTRI/2021/03/031855; principal investigator: Dr. Nishant Patel and Dr. Aritra Kundu; date of registration: March 10, 2021), patients were recruited to participate in this prospective randomized controlled trial. The study was conducted between September 2021 and January 2023 in the operating rooms of maxillofacial and otorhinolaryngology surgery, in accordance with the Ethical Principles for the medical Research Involving Human Subject outlined in the Declaration of Helsinki of 1975 (revised in 2013). Informed written consent was obtained from each patient in accordance with relevant guidelines and regulation. Patients aged between 18 and 75 years, scheduled for elective maxillofacial and otorhinolaryngology surgeries, were screened for this study. Eligibility included an anticipated difficult intubation and a planned nasotracheal intubation. All patients underwent evaluation in the pre-anesthesia clinic for assessment of difficult airway, which included: mouth opening restricted to 1.5–2.5 cm, a modified Mallampati grading of 4, neck extension less than 70°, a positive upper lip bite test, a medical history of radiotherapy, the presence of any head or neck tumors, or a history of previous difficult intubation with American Society of Anesthesiologists (ASA) physical status classification of I-III. The patients with ASA Status IV or more, with brady-arrhythmias, heart failure, the base of skull fracture, emergency surgery, thrombocytopenia or coagulopathy and patients with nasal pathology were excluded.


2.1


Randomization and blinding


All recruited patients were randomly assigned using computer-generated simple randomization methods in a 1:1 sequence. They were assigned either to the flexible bronchoscope (FB) group or the CMAC D blade video-laryngoscope (VL) group using a sequentially numbered opaque sealed envelope method. The randomization sequence was generated before the commencing of study. Group allocation was concealed in 100 sealed envelopes. These were then sealed and shuffled into a random order before being numbered with sequential study identification numbers. Patients, the statistician assessing the outcome data, and the investigator evaluating the patients in the postoperative period were blinded to the group allocations. However, due to the nature of the study involving two different devices, the primary investigator could not be blinded. An independent investigator, who was not part of the study, generated the random allocation sequence, enrolled the participants, and assigned them to their respective interventions.


2.2


Study protocol


All patients were transferred to the surgical theatre complex and nebulised with lidocaine 4 % (4–5 ml) with oxygen at 5–6 l/min in the preoperative waiting room. According to the British Thoracic Society’s guidelines for bronchoscopy, a maximal dose of 10–15 ml lidocaine 4 % was allowed (not more than 9 mg/kg of lean body weight) [ , ]. Two puffs of lidocaine 10 % spray (one metered dose of ‘puff’ delivers 0.1 ml, i.e., 10 mg lidocaine) were applied to the tonsillar pillars and the back of the throat. Patients were instructed to gargle with the medication in their oral cavity until the upper airway was numb. Patients also received topical nasal drops of xylometazoline (0.1 %), with two drops administered in each nostril, and 0.2 mg intramuscular glycopyrrolate half an hour before intubation.


The effectiveness of topical anesthesia was evaluated by the patient’s acceptance of the nasopharyngeal airway in both groups. Following this, an oropharyngeal airway was inserted to check the adequacy of oropharyngeal anesthesia. After the attending anaesthesiologist confirmed sufficient topical anesthesia, the envelope was opened; revealing the group allocation and the randomized technique of intubation was implemented. Standard monitoring and Bispectral Index (BIS; Medtronic- Covidien, Dublin, Ireland) monitors were attached in the operating room, and baseline values were recorded. The patients received supplemental oxygen via nasal prongs at 2–4 L/min at the beginning of sedation, which was kept on throughout the procedure. Patients were sedated with an initial loading dose of 1 mcg/kg of dexmedetomidine over 10 min in both groups, followed by infusion at 0.4 mcg/kg/hr. The time to reach a BIS score of ≤80, sustained for at least 30 s and RSS of ≥2 was noted in both groups. Once the attending anaesthesiologist deemed the sedation adequate, a well-lubricated soft nasopharyngeal tube was inserted into the nasal tract using lidocaine jelly. For tracheal intubation, either a C-MAC D-blade (Karl Storz Endoskope SE & Co. KG, Tuttlingen Germany) or a flexible bronchoscope (11301 BN1 outer diameter 5.2 mm; Karl Storz, Tuttlingen, Germany) was used. Cuffed reinforced tracheal tubes with internal diameter 6.0–7.5 mm were used in all patients, as per the discretion of the intubating anaesthesiologist before the information about the randomization.


The attending anesthesiologist, either a senior registrar or consultant, performing the intubation had completed at least 50 previous intubations using both a video-laryngoscope and a flexible bronchoscope before the study. To optimize tracheal intubation, the anesthesiologists were allowed to use external manipulation of the larynx, a change in head positioning, or Magill forceps. The sequence of these manoeuvres was left to the discretion of the anesthesiologist.


In the FB group, initially, the flexible bronchoscope was passed through the nostril to the carina and then the tracheal tube was railroaded. However, in the VL group, the CMAC D-blade VL was placed in the oral cavity for glottis visualization, after that the tracheal tube was passed through the nostril into the glottis. In the VL group, we suppressed the cough reflex by spraying 4 % lidocaine around the glottis under vision with gentle laryngoscopy pressure, or we used the spray-as-you-go technique for the FB group.


In the event, that a patient experiences discomfort or intolerance during the procedure, a bolus of Propofol was administered in aliquots of 0.2–0.5 mg/kg, and the total amount of propofol used was noted. If the anesthesiologist was unable to perform successful tracheal intubation after three attempts, the intubation attempt was considered unsuccessful. The patient was intubated after giving general anesthesia at the discretion of the attending anesthesiologist.


The intraoperative maintenance of anesthesia and extubation process is carried out at the discretion of the attending anesthesiologists. All the patients were transferred to the post anesthesia care unit (PACU) post-operatively. During this time, non-invasive blood pressure (NIBP), ECG, SpO2 and respiratory rate (RR) were monitored and recorded for all the patients.


2.3


Study outcomes


2.3.1


Primary outcome, intubation time


Intubation time was divided into phases 1 and 2. Phase 1 was from the insertion of tracheal tube in the nasal cavity for video-laryngoscope group or insertion of tracheal tube mounted on the flexible bronchoscope in the nasal cavity to the visualization of the glottis. Phase 2 was defined from visualization of glottis till the appearance of the 3 square wave of capnograph. The sum of the timings of phase 1 and phase 2 was calculated as the total intubation time.


2.3.2


Secondary outcome


The secondary outcomes noted were first attempt success rate with overall success rate, intubation score, amount of propofol used for rescue, adverse events, anesthesiologist’s satisfaction score and patients’ satisfaction score. These parameters were noted by an independent observer unaware of the study methodology.


2.3.2.1


Intubation success rate


Only three intubation attempts were allowed for each patient. The attempt was declared failed if the anesthesiologist failed with tracheal intubation despite all maneuvers and propofol rescue bolus. An intubation attempt was defined when the FB was removed from the nose, or VL was removed from the mouth without negotiating the tracheal tube into the glottis. Once the procedure was declared unsuccessful, the patients were intubated at the discretion of the attending anesthesiologist.


2.3.2.2


Nasal intubation score [ , ]


The patient’s response to the introduction of the tracheal tube was evaluated using the nasal intubation scoring (see Table 1 ). If the nasal intubation score exceeded 4, indicating severe gagging or coughing, two additional puffs of 10 % lidocaine were administered under direct vision. A rescue bolus dose of propofol (@ 0.2–0.5 mg/kg) was also given, and intubation was reattempted-after-60-s.



Table 1

Nasal intubation score.



















Vocal cord movement Coughing
1 = Open 1 = None
2 = Moving 2 = One gag or cough only
3 = Closing 3= >1 gag or cough, but acceptable
4 = Closed 4 = Unacceptable condition

Min score 2; Max Score 8.


The intubation score was calculated based on vocal movement (1–4 points) and coughing (1–4 points). Individual scores were added to obtain the final score, which ranged from a minimum score of 2 to a maximum score of 8.


2.3.2.3


Anesthesiologists’ satisfaction score


Anesthesiologists rated their satisfaction with the intubation attempts on a numerical rating scale. It was a subjective scoring derived for this study (refer Table 2 ). Based on this scoring system-a score of 1 was given when the anesthesiologist was most satisfied, a score of 2 was given for mild satisfaction, a score of 3 was given for some dissatisfaction and a score of 4 was given for most dissatisfaction [ ].



Table 2

Anesthesiologists’ and patients’ satisfaction score.



















Anesthesiologist’ satisfaction score Patients’ satisfaction score
1 = most satisfaction 1 = no facial grimace
2 = minimal satisfaction 2 = mild facial grimace
3 = some dissatisfaction 3 = moderate facial grimace
4 = most dissatisfaction 4 = severe facial grimace.


2.3.2.4


Patient’s satisfaction score [ ]


Patient’s satisfaction score ( Table 2 ) during the intubation was rated as: 1 = no grimace, 2 = mild grimace, 3 = moderate grimace and 4 = severe grimace. After 24 h of surgery, a visit was done to record any recall during intubation and the incidence of hoarseness and sore throat was noted.


2.3.2.5


Adverse events


Any adverse events during intubation, such as desaturation (SpO2<94 %), the use of atropine or ephedrine for hemodynamic support and, major nasal bleeding requiring intervention, were noted.


3


Sample size calculation and statistical analysis


In a previous study conducted by Kramer et al. the time to nasotracheal intubation using a flexible bronchoscope in patients with limited mouth opening was found to be 94 s [ ]. To achieve a 50 % reduction in nasotracheal intubation time with the video-laryngoscope, we took a conservative standard deviation of 80 s. With an alpha error of 0.05 and a power of 80 %, a total of 90 patients were required for the study. Anticipating a dropout rate of 10 %, we ultimately recruited 100 patients, with 50 patients assigned to each group. Statistical analysis was carried out using SPSS software (IBM SPSS Statistics 26). The normality of the data distribution was assessed using the Kolmogorov-Smirnov test. For data that did not follow a normal distribution, we employed non-parametric tests. The following statistical methods were applied to analyze the results:



  • 1.

    For comparing quantitative variables that were not normally distributed, we used the Mann-Whitney test for two groups. The Independent t -test was used for comparing normally distributed data between two groups.


  • 2.

    For qualitative variables, the Chi-Square test was utilized. If any cell had an expected value of less than 5, Fisher’s exact test was applied.


  • 3.

    A p-value of less than 0.05 was considered statistically significant for all analyses.



4


Results


One hundred patients were enrolled in the study, with 50 randomly allocated to either the FB group or the VL group. There were no dropouts in any of the groups. Intubation was successful in 49 patients in the FB group and 48 in the VL group ( Fig. 1 . CONSORT Diagram).


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May 11, 2025 | Posted by in ANESTHESIA | Comments Off on Flexible bronchoscope versus video-laryngoscope for nasotracheal intubation in patients with anticipated difficult airway under topical anesthesia and dexmedetomidine infusion: A randomized controlled trial

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