Fibrescope vs Videolaryngoscope for Nasotracheal Intubation

Introduction

The technique of inserting a tracheal tube through the nasal passage into the trachea (airway) is known as nasotracheal intubation. This is the preferred airway for surgical procedures performed in and around oral cavity including dental procedures. Traditionally, the tracheal tube is initially inserted blindly into the nasal cavity. A laryngoscope is then used to visualise and help guide the passage of the tube into the trachea. This approach can be associated with difficulty passing the tube and a high incidence of nasal trauma [1, 2], as the nasal passages can be narrow and demonstrate inter-individual anatomic variability.

Various approaches have been described in the literature to reduce nasal trauma including warming the tube [3], applying water-based lubricants and preparing the nasopharynx with progressive dilation and/or a topical vasoconstrictors [4]. There have been randomised studies using curve-tipped suction catheters [2], and bougies [1,5] showing reduced incidence of nasal trauma as compared to blind passage of the tube through the nose. However, as these devices are blindly inserted through the nasal passage, the device itself can cause some degree of trauma.

The investigators hypothesise that the use of the flexible fibrescope could reduce nasal trauma and bleeding whilst improving first time intubation success rates, when compared to video laryngoscope-assisted nasal intubation. Using a fiberscope allows for an assessment of the patency of the nasal passages and visualisation of the path the tube will take through the nasopharynx.

In current practice, both flexible fibrescopes and video laryngoscopes are routinely used for tracheal intubation. However, with video laryngoscopy during nasal intubation, insertion of tube through the nasal passage is blind. Therefore, some practitioners prefer using a fiberscope for nasal intubation. Clinicians are uncertain as to which is the best approach. To our knowledge, previous studies have not utilised flexible fibrescopes to eliminate blind insertion of the tube in the nostril. Comparing the efficacy of a flexible fibrescope with a tracheal tube railroaded over it to a video laryngoscope for nasotracheal intubation could inform airway practitioners on their choice of technique to improve success and minimise bleeding risk.

Methods

On arrival to theatre, following a standard WHO surgical safety check list and application of routine monitoring, patients will be randomly allocated to either flexible fibrescope or video laryngoscope to facilitate nasotracheal intubation. All patients will receive decongestant nasal spray of 5% lidocaine with 0.5% phenylephrine 1 ml in each nostril.

Both a flexible fiberscope and a video laryngoscope will be available in the anaesthetic room prior to revelation of the group.

All other aspects of patient care outside of the randomisation to fibrescope or video laryngoscopy for nasotracheal intubation will be conducted in accordance with routine clinical practice and local guidelines.

For patients randomised to the video laryngoscope, laryngoscopy will be performed using the video laryngoscope: Mcgrath ™ MAC video laryngoscope (Medtronic Plc, Galway Ireland). A lubricated 6.0 mm ID tube: Polar™ Preformed Tracheal tube, North Nasal Profile™ (Smiths Medical ASD, Inc, Minneapolis, USA) will be inserted through the most patent nostril (as identified during preoperative visit) and advanced until it reaches the posterior nares. It will be then advanced through the vocal cords into the trachea under video guidance. If there was any hold-up immediately after passing the tube through the nostrils, the tube will be gently rotated to allow passage through the nasopharynx. If there is any impingement at the level of arytenoids, the tube will be withdrawn slightly, rotated anticlockwise and then advanced.

For patients randomised to the fiberscope, the same tube type will be loaded on the 4mm fibrescope: Flex. Intubation Video Endoscope 4 x 65 - model 11302BDX (Karl Stortz Tuttlingen, Germany) prior to beginning intubation. The fibrescope will then be inserted into the most patent nostril. If this nostril is deemed to be adequate by the operator, the procedure will continue, otherwise the other nostril will be assessed and the most optimal nostril will be chosen for intubation. The fibrescope will be advanced through the nasopharynx and into the trachea. At this point the tube will be advanced over the fiberscope from the trachea.

Correct placement of the tube will be confirmed using end tidal CO2 and once nasotracheal intubation is completed the rest of the anaesthetic management will proceed as planned by the lead anaesthetist.

During nasotracheal intubation the data collected will include severity of nasal trauma on a 4 point scale, smoothness of nasal intubation on a 4 point scale , laryngoscopy time (from insertion of laryngoscope in the mouth to visualize the vocal cords or from insertion of fiberscope in the nostril to visualise the vocal cords), intubation time (time from insertion of fiberscope or video laryngoscope till first capnography trace) and first attempt success rate (% of intubations succeeded in first attempt), number of intubation attempts and any additional manoeuvres required (external pressure on thyroid cartilage, tube rotation, tube impingement).

Follow-up assessments

Patients will be reviewed in the first 3 to 24 hours whilst they are in the hospital, as apart a standard postoperative visit, where an assessment of patient-centred secondary outcomes will be made. No further follow up is required for this study. If any patients report continuing nasal bleed in the postoperative period, a maxillofacial surgeon will be requested to review the patient for further management and any outcome data may be collected up to 72 hours.

Consent

Participants will be given adequate time to read and understand the patient information leaflet. Once they have read the information, any questions will be answered. If they agree for the study, they will be asked to complete the consent form. The consent will be obtained by chief investigator, principal investigator or one of the research team members delegated and supervised by the investigators.

Sample size

Sample size is based on the primary outcome of incidence of nasal bleeding. A previous study of video laryngoscope assisted nasotracheal intubation reported a rate of bleeding detected in the posterior pharynx of 68% (Abrons 2017). A relative reduction in 33% is considered clinically significant. To detect this treatment difference at a significant level of 5% and power of 90%, a total sample of 186 patients is required. To account for failure and loss of follow up, the investigators will recruit a total of 200 patients.

Randomisation Methodology

Participants will be randomised using a paper randomisation list that will be provided to the UHCW Research and Development (R\&D) department, independent from the rest of the study team. The randomisation list will be generated by the study statistician prior to recruitment starting. The method of permuted random blocks will be utilised, with varying block sizes used.

Blinding

It will not be possible to blind the investigator to the type of device used. However, 5 minutes after completion of intubation, the operating surgeon (who is blinded to the technique of intubation) will examine the oropharynx and record the bleeding. At the time of intubation, the investigator will record the bleeding as seen on video laryngoscope or fiberscope monitor screen.

Assessment and management of risk

For this study, patients requiring general anaesthesia and nasotracheal intubation for elective surgical procedures will be recruited. The flexible fibrescope and video laryngoscope selected for this study are currently used in routine clinical practice as intubation aids. In the event of any unanticipated difficulty with intubation, the lead anaesthetist will follow the Difficult Airway Society guidelines and data collection will stop at this point.

The lead anaesthetist is free to choose different airway equipment to those specified by the study if they feel that this would be clinically appropriate. The investigators do not anticipate any additional risks to the study participants. During the procedure of airway management, all patients will be closely monitored as specified by 'Association of Anaesthetists' standards of monitoring during anaesthesia. This includes peripheral oxygen saturation, end tidal oxygen, depth of anaesthesia and end-tidal CO2, ECG and blood pressure.

References

1. Abrons RO, Zimmerman MB, El-Hattab YMS. Nasotracheal intubation over a bougie vs. non-bougieintubation: a prospective randomised, controlled trial in older children and adults usingvideolaryngoscopy. Anaesthesia 2017; 72: 1491-500.
2. Morimoto Y, Sugimura M, Hirose Y, Taki K, Niwa H. Nasotra- cheal intubation under curve-tipped suction catheter guidance reduces epistaxis. Canadian Journal of Anesthesia 2006; 53: 295-8
3. Kim YC, Lee SH, Noh GJ, et al. Thermosoftening treatment of the nasotracheal tube before intubation can reduce epistaxis and nasal damage. Anesthesia and Analgesia 2000; 91: 698- 701.
4. El-Seify ZA, Khattab AM, Shaaban AA, Metwalli OS, Hassan HE, Ajjoub LF. Xylometazoline pretreatment reduces nasotra- cheal intubation-related epistaxis in paediatric dental surgery. British Journal of Anaesthesia 2010; 105: 501-5.
5. Bansal T, Singhal S, Dhingra K. A study to evaluate nasotracheal intubation using Airtraq laryngoscope with a bougie and without a bougie. Indian J Anaesth 2022;66:757-62.
6. Collins SR, Blank RS. Fiberoptic intubation: an overview and update. Respir Care. 2014 Jun;59(6):865-78; discussion 878-80. doi: 10.4187/respcare.03012. PMID: 24891196.
7. Hansel, J., Roger, A.M., et al. (2022) Videolaryngoscopy versus direct laryngoscopy for adults undergoing tracheal intubation, Cochrane Database of Systematic Reviews, 4(4), CD011136. Available at https://pubmed.ncbi.nlm.nih.gov/35373840/ (Accessed 5 July 2023)