Preoperative rigid laryngoscopic examination and modified jaw thrust manoeuver during fibreoptic-assisted tracheal intubation for general anaesthesia

Abstract

Preoperative laryngoscopic examination of the airway informs general anaesthesia management and planning. However, the same glottic opening view cannot always be obtained during direct laryngoscopy of anaesthetised patients. In this case report, a patient underwent preoperative rigid laryngoscopy due to medical history, and no problems were anticipated in performing tracheal intubation; however, the direct laryngoscopic view was a Grade 4 on the Cormack-Lehane Scale after anaesthesia induction. A jaw thrust manoeuvre to facilitate fibreoptic-assisted nasotracheal intubation was not feasible. In order to compensate, a modified method of jaw thrust was implemented, where both thumbs were placed on the floor of the patient’s mouth, leading to a successful result. Safe airway management should be implemented with proper planning based on a careful preoperative evaluation.

Background

Preoperative airway assessment is an indispensable component of safe anaesthesia practices. Difficult or failed tracheal intubation can lead to serious consequences such as brain damage and death.¹ Patients with demonstrated or suspected pathology in the upper respiratory tract must undergo a more in-depth airway evaluation before general anaesthesia, including a laryngoscopic examination by an otolaryngologist.² Preoperative laryngoscopy provides a detailed anatomical view of the laryngeal structures and a view of the proximal trachea.

When fibreoptic-assisted tracheal intubation is performed on an anaesthetised patient, airway collapse may impede access to the glottic opening. Many airway clearance methods have been proposed to overcome this problem and facilitate intubation, including airway devices for route guidance, direct laryngoscopy, jaw thrust and lingual traction.³

In this report, a patient underwent preoperative rigid laryngoscopy that indicated no tracheal intubation problems were expected; however, the direct laryngoscopic view was a Grade 4 on the Cormack-Lehane Scale after anaesthesia induction. In order to compensate, a modified method of jaw thrust was implemented, where both thumbs were placed on the floor of the patient’s mouth, leading to successful fibreoptic-assisted nasotracheal intubation. We report this case to describe how preoperative laryngoscopy should be applied to anaesthesia practice and introduce a modified jaw thrust method used to achieve fibreoptic-assisted nasotracheal intubation in a case where the conventional jaw thrust could not be performed.

Case presentation

A 68-year-old woman was scheduled for excision of a recurrent oral cancer under general anaesthesia. She had already undergone hemimandibulectomy with supraomohyoid neck dissection and reconstruction with fibula free flap for excision of oral cancer 1 year prior. Her Cormack-Lehane Scale Grade was 1, and no adverse events during anaesthesia induction, maintenance and recovery were reported for this surgery. Postoperative radiotherapy was applied due to perineural invasion on pathology.

At the preoperative visit, an airway examination revealed a mouth opening of 2.5 fingers’ breadth, limited neck extension, a thyromental distance of 6.5 cm, an edentulous mandible and a Mallampati Class 3 airway. A rigid laryngoscopic examination with 10% lidocaine spray was performed by an otolaryngologist who consulted on the airway evaluation and revealed non-specific appearances of the epiglottis, arytenoid cartilage and hypopharynx (figure 1). Vocal cord mobility was normal. The consultation concluded that there was no risk of difficulty in tracheal intubation for general anaesthesia. Although there were limitations in patient neck extension, anaesthesia induction was planned using a standard method of conventional direct laryngoscopy as there were no problems identified in previous anaesthesia records or preoperative laryngoscopy findings.

Figure 1.

Preoperative rigid laryngoscopic view of the glottic opening.

After arriving in the operating room, standard monitoring commenced, including ECG, non-invasive blood pressure and pulse oximetry. Vital signs were within normal limits. Anaesthesia was induced with intravenous propofol and remifentanil using a target-controlled infusion pump (Orchestra Base Primea, Fresenius Kabi, Brézins, France). The target effect site concentrations for propofol and remifentanil during induction were 4 µg/mL and 4 ng/mL, respectively. After confirming that the lungs could be easily ventilated with a face mask, intravenous rocuronium was administered. The train-of-four and bispectral indices were monitored.

A nasotracheal tube (6.5 mm internal diameter) was gently inserted through the left naris, and the direct laryngoscope was introduced into the mouth. The direct laryngoscopic view at this point was a Grade 4 on the Cormack-Lehane Scale. The nasotracheal tube was withdrawn, and flexible fibreoptic bronchoscopy was attempted with the jaw thrust manoeuvre. However, jaw thrust on the deformed and edentulous mandible was ineffective. Previous supraomohyoid neck dissection surgery and radiotherapy limited lengthening of the soft tissue around the neck (figure 2), and bronchoscopy did not provide a sufficient view of the glottis opening.

Figure 2.

Edentulous and deformed mandible after reconstructive surgery. Asterisks show the scar from the previous surgery.

The assistant modified the standard method and placed both thumbs in the patient’s mouth, firmly fixing them to the floor of the mouth. They used the rest of their fingers to grasp the patient’s mandibular ramus like a hook. Thus, the mandible was pulled forward, and the flexible fibreoptic bronchoscope could more easily approach the glottis; subsequent nasotracheal intubation was successful. During the surgery, propofol and remifentanil were infused at target effect site concentrations of 2.8–3.2 ng/mL and 3.0–3.5 µg/mL, respectively, and an O₂/air mixture was used.

Outcome and follow-up

Total surgical time was 3 hours 10 min; no adverse events occurred. The patient was extubated when she could open her eyes and respond to verbal commands using train-of-four monitoring and sugammadex administration. She was able to breathe spontaneously without the aid of oral airway or assisted ventilation. There were no adverse airway events in the postanaesthesia care unit or general ward.

Discussion

This case report addresses two issues. The first is how preoperative laryngoscopy is interpreted and applied in anaesthesia practice, and the second is the introduction of a modified jaw thrust method to facilitate flexible fibreoptic-assisted tracheal intubation in patients with head and neck pathologies.

Endoscopes used to examine laryngeal lesions include a rigid and flexible laryngoscope.⁴ In our institution, the rigid laryngoscope is used to obtain a clear, magnified view, and a flexible laryngoscope is used when a functional assessment during continuous speech is required. Rigid telescopic laryngoscopy is performed using a 70° or 90° angled telescope placed transorally with the patient seated.⁵ A 70° telescope (Machida LY-C30, Tokyo, Japan) connecting to a high-resolution endoscopic video camera system was used in the case reported here (figure 3). Direct laryngoscopy for tracheal intubation necessitates a direct view of the glottis within a narrow view angle of approximately 10–15°⁶; however, the 70° telescope provides a more angled and indirect view. In this case, the rigid telescope’s view angle was not appreciated by the anaesthesiologist before anaesthesia. We recommend that anaesthesiologists and otolaryngologists collaborate to discuss what equipment was used during the preoperative laryngeal endoscopy.

Figure 3.

Rigid telescopic laryngoscope used in preoperative examinations. The dotted line represents the field of view provided by this 70° telescope.

The glottic view may also be affected by soft tissue tone around the airway under anaesthesia and due to patient position, which, in this instance, differed from the preoperative examination. Zhang and Li⁷ reported two laryngeal cyst cases presenting significant differences between preoperative laryngoscopic findings and airway assessment after anaesthesia induction. They used a video laryngoscope for tracheal intubation, but such equipment was not available for our patient. It might have been easier to secure the airway if a video laryngoscope had been used instead of a direct laryngoscope.

Preoperative laryngoscopy findings provide functional and anatomical information of the larynx and proximal airway. However, we suggest that these findings may only be relied on to the extent that there are no anatomical problems around the glottis; in such cases, further consideration must be given to the potential for problems with accessing the glottis with an endotracheal tube. Sufficient mouth opening and sniffing position are needed to see the larynx and glottis with a direct laryngoscope. After anaesthesia induction, it is essential to consider changes in the soft tissue that affect the visual field.

It should be acknowledged that the limitations in neck extension identified before surgery were overlooked in this case. Previous surgery or radiotherapy to the head and neck can be significant predictors of airway challenges.⁸ Accordingly, an advanced airway management plan should have been designed during anaesthesia planning based on the patient’s medical history and preoperative evaluation. When difficult airway management is expected, awake fibreoptic intubation is considered the standard approach, especially when difficulties with mask ventilation are expected.^{9 10} We believe awake fibreoptic intubation would have been ideal for the induction of anaesthesia in this patient, especially because a video laryngoscope was not available. The non-implementation of awake fibreoptic intubation was attributed to underestimating the patient’s airway-related issues and accepting the otolaryngologist’s opinion of the preoperative laryngoscopy without a full understanding of the instrument used during the assessment.

The jaw thrust manoeuvre facilitates the advancement of the flexible fibreoptic bronchoscope into the trachea and increases success rates during oral fibreoptic-assisted tracheal intubation.¹¹ In this case, the patient had an edentulous and deformed mandible that had undergone significant reconstructive surgery due to tumour excision. It was difficult to grasp and pull in a conventional jaw thrust manner (figure 4A). Limits in soft tissue pliancy made this more difficult. The modified method enabled a more accurate and efficient jaw thrust suitable for the edentulous and deformed mandible (figure 4B). Iqbal et al described an anterior jaw lift manoeuvre in which the assistant extends the patient’s head by putting one hand on the occiput and inserting the thumb of the other hand into the patient’s mouth to grasp the mandible and pull it forward.³ In that study, an anterior jaw lift with head tilt provided a better view of the glottis opening than the route guidance airway device.

Figure 4.

Conventional jaw thrust manoeuvre performed by an assistant during fibreoptic-assisted tracheal intubation (A). Modified jaw thrust manoeuvre of placing the thumbs on the floor of the mouth and pulling the jaw forward (B).

Conversely, Park et al suggest a neutral head position provides a better view of the glottic opening than the sniffing position during oral fibreoptic intubation.¹² Our case, unlike these studies, required nasotracheal intubation. Further study on head positions during fibreoptic-assisted tracheal intubation might enable more efficient procedures.

Airway clearance methods for fibreoptic-assisted tracheal intubation include airway devices for route guidance, direct laryngoscopy, jaw thrust and lingual traction.³ Durga et al reported that a combination of jaw thrust and lingual traction cleared the airway more effectively than either manoeuvre alone.¹³ In our case, modified jaw thrust alone was sufficient for airway access, perhaps because the angle from the nasopharynx to the glottic opening was less acute than for fibreoptic-assisted oral intubation and thereby less disturbed by tongue retraction. As lingual traction requires another assistant, this should be anticipated if the need is expected. The most helpful airway clearance method will vary depending on the bronchoscope access route, the patient’s anatomical singularities and the anaesthesiologist’s experience. Procedures should be applied with full consideration of these factors.

Despite various factors suggesting difficult airway, the preoperative laryngoscope findings were accepted at face value, which led to difficulties in airway management for general anaesthesia; the cause of the error is thought to be a lack of understanding of rigid laryngoscopy. Awake fibreoptic intubation often takes time to perform; however, it is a reliable and safe airway management method that should be actively considered when a difficult airway is predicted. In addition, a modified method of jaw thrust in which both thumbs were placed on the floor of the patient’s mouth can facilitate fibreoptic-assisted tracheal intubation.

Learning points.

• Preoperative laryngoscopy provides essential information for airway evaluation and management planning for general anaesthesia; nonetheless, it should be acknowledged that the same glottic opening view cannot always be obtained during the direct laryngoscopy performed on anaesthesia-induced patients. The anaesthesiologists should be aware that the preoperative laryngoscopy was conducted with the patient awake and sitting up. They must also understand how to interpret the results in the context of the equipment used.

• The modified jaw thrust manoeuvre, in which the mandible is held like a hook with both thumbs in the patient’s mouth, can be a useful alternative to clear the airway for fibreoptic-assisted tracheal intubation. If the conventional jaw thrust manoeuvre is not feasible due to the patient’s anatomy, as in this case report, a hook-like jaw thrust is worth attempting.

• Safe airway management should be implemented with proper planning based on a careful preoperative evaluation that includes all the information collected.