The left molar approach assisting fibreoptic intubation

We present details of a technique combining conventional and fibreoptic laryngoscopy to allow tracheal intubation in a case of unexpected difficult intubation. A 57-year-old, 75-kg man was scheduled for elective sigmoid colectomy for a non-obstructing adenocarcinoma of the colon. Pre-operative assessment of his airway revealed a Mallampati grade 2 pharyngeal view, good jaw thrust and Patil distance greater than 6 cm; however, inward sloping upper incisors were noted (Figure 1 -4. ECG, non-invasive blood pressure and pulse oximetry were applied on arrival in the anaesthetic room. A thoracic epidural was sited after obtaining intravenous access and then the patient was laid supine. Anaesthesia was induced with fentanyl 0.1 mg and propofol 150 mg. After checking that mask ventilation was possible, muscle relaxation was produced with atracurium 40 mg. Anaesthesia was maintained with sevoflurane 4% in oxygen. Laryngoscopy with Macintosh size 4 and McCoy size 3 blades was difficult because of the sloping teeth and decreased submandibular compliance. No view of the epiglottis or other laryngeal structures could be obtained. A gum elastic bougie was inserted blind and a 7-mm tracheal tube railroaded over it. Capnography revealed a small amount of carbon dioxide with each breath over approximately 20–30 s but clinical inspection of chest movements and auscultation suggested oesophageal intubation. The tube was therefore removed. Manual ventilation was still possible although becoming more difficult. A second consultant with considerable experience in fibreoptic intubation was now present, as was a fibreoptic laryngoscope. Anaesthesia was maintained with boluses of propofol. At no point did the measured oxygen saturation fall below 96%. Oral fibreoptic laryngoscopy was performed in combination with external jaw thrust and laryngeal manipulation. The tip of the epiglottis was seen pressed against the posterior laryngeal wall; the fibrescope could not be guided beyond it. Manual lifting forward of the tongue was tried but failed to improve the situation. At this stage, the size 4 Macintosh blade was reintroduced using the left molar approach [1]. With the Macintosh blade in place, the fibreoptic scope was again used and the posterior portion of the arytenoid cartilages could be seen. The fibrescope was guided into the trachea and the mounted 7-mm tracheal tube was railroaded with some difficulty into the trachea. Capnography and auscultation were used to confirm correct placement of the tube. Anaesthesia and surgery proceeded uneventfully using the epidural for analgesia and maintaining anaesthesia using sevoflurane in an air/oxygen mix. At the end of surgery, neuromuscular blockade was antagonised using neostigmine 2.5 mg with glycopyrronium 0.5 mg, and a peripheral nerve stimulator was used to ensure complete reversal of blockade. Sevoflurane was stopped and the trachea was extubated with the patient fully awake in the sitting position. The following day, the patient was reviewed. The difficulty in tracheal intubation was explained, his notes were marked and he was given a letter outlining the problem for future reference. The patient had no recollection of the events but did complain of a sore throat and a swollen tongue. This case illustrates several points: Airway assessment may be falsely reassuring as difficult intubation is rare [2]. Inflation of the stomach during mask ventilation may potentially produce a confusing capnograph trace if the oesophagus is subsequently intubated. Use of a conventional laryngoscope via the left molar approach can allow identification of laryngeal structures using the fibreoptic laryngoscope. The use of fingers and the McCoy laryngoscope have been described previously to aid passage of tracheal tubes through the laryngeal inlet during fibreoptic intubation [3]. Combined use of conventional and fibreoptic laryngoscopy has also been described in a case that was clearly predicted to be difficult [4]. We believe that this is the first description of the left molar approach to conventional laryngoscopy being used to facilitate recognition of laryngeal structures by the fibreoptic laryngoscope.