By introducing a lozenge containing 100-mg lidocaine concealed in liquorice powder and aspartame, we aimed to reduce patient discomfort by avoiding the invasive trans-tracheal injection for awake intubation, as this is a very unpleasant procedure.1,2 The lozenge is custom made to release the lidocaine over 10 min to anaesthetise the pharynx in the awake patient allowing intubation with McGrath Videolaryngoscope (Aircraft Medical Limited, Edinburgh, UK).
This feasibility study included 16 consecutive elective patients with anticipated difficult intubation scheduled for bariatric surgery under general anaesthesia. Inclusion criteria were as follows: age 18 to 70 years; able to understand and speak Danish; and able to give informed oral and written consent to participate. Exclusion criteria were as follows: known lidocaine allergy and pregnant or nursing women. Mallampati score and BMI were used to assess the anticipated difficulty of the intubation.
Ethical approval for this study (Ethical Committee No H-B-2008–062) was provided by the Ethical Committee B for the Capital Region, Denmark (Chairperson Lars Hviid) on 26 August 2008 and registered at www.clinicaltrials.gov (NCT00791024). The study was carried out according to good clinical practice (GCP) and monitored by the GCP Unit at Copenhagen University Hospital.
The lozenges were manufactured by the Pharmacy of the Capital Region. Xylocaine spray (AstraZeneca, Södertälje, Sweden), 4-mg lidocaine was used below the vocal cords as an additional local anaesthetic to the lozenges. For inspection of the oro-pharyngeal cavity, to facilitate the tracheal intubation, the McGrath Videolaryngoscope (Aircraft Medical Limited) was used.
No sedatives were administered as premedication. To obtain oro-pharyngeal anaesthesia, the lidocaine lozenges were administered 10 min prior to intubation. After oro-pharyngeal anaesthesia, the McGrath Videolaryngoscope was used to apply additional anaesthesia with Xylocaine spray on and beneath the vocal cords before tracheal intubation. Remifentanil infusion 0.15-μg kg−1 ideal body weight × −1 was used to calm the patient during the procedure. Only two consultants performed the tracheal intubations. If the McGrath Videolaryngoscope intubation failed a fibreoptic scope was used. Immediately after intubation, general anaesthesia was induced with propofol and remifentanil.
Then the anaesthetist estimated the difficulty of the intubation on a questionnaire and registered time used for overview and intubation of the airway.
The following day, the patients were interviewed regarding their perception of the method by a four-point scale: 1, no discomfort; 2, slight discomfort; 3, moderate discomfort; and 4, severe discomfort. Patient satisfaction was evaluated, asking the patients to state if they would recommend the procedure to others. Patients were also asked to evaluate the taste and texture of the lozenges.
Patients’ details are presented in Table 1. Twelve patients were successfully intubated using the McGrath Videolaryngoscope. Four patients had fibreoptic intubation due to severe gag reflexes. All patients were awake during intubation and all had a clear memory of the procedure. The median time to obtain adequate view for intubation with the McGrath Videolaryngoscope was 7.9 s. (range 1 to 20 s.), and the median time to intubation was 8.2 s. (range 1 to 20 s). The combined time for overview of the airways and the intubation in all patients was within 30 s. No additional local anaesthesia in the pharynx was needed in any of the 16 cases, no patients experienced postoperative discomfort from the pharynx and no complications were encountered in any of the patients.
The anaesthetists assessed 85% of the intubations to be either very easy or easy to perform. Sixty-three percent of the patients scored the procedure: slight discomfort or no discomfort. All patients found the taste and texture of the lozenges to be good or neutral. All patients would recommend the procedure to others.
Life-threatening situations can occur during induction of anaesthesia when tracheal intubation is performed. Awake intubation is a way to avoid such situations, but is considered unpleasant for most patients. Several methods have been used for topical anaesthesia of the airway including nebulisation3 and trans-tracheal injection of local anaesthetics prior to awake intubations. Unfortunately, these methods are unpleasant and time-consuming, and a very high dosage of lidocaine is necessary for nebulisation.3
We have developed a new method for analgesia in awake laryngoscopic intubation in patients with anticipated difficult intubation with lidocaine lozenges and video laryngoscopic intubation. The new method was acceptable and beneficial for both patients and anaesthetists. Our data indicate that the combination of an effective topical analgesia and the McGrath is a safe, easy and effective method for awake oro-tracheal intubation. As this feasibility study is a description of a new way of topical analgesia of pharynx other types of laryngoscopes might be used as well as the McGrath Videolaryngoscope.
Assistance with the study: none declared.
Financial support and sponsorship: none declared.
Conflicts of interest: none declared.
1. Joo HS, Kapoor S, Rose DK, Naik VN. The intubating laryngeal mask airway after induction of general anesthesia versus awake fiberoptic intubation in patients with difficult airways. Anesth Analg
2. Simmons ST, Schleich AR. Airway regional anesthesia for awake fiberoptic intubation. Reg Anesth Pain Med
3. Williams KA, Barker GL, Harwood RJ, Woodall NM. Combined nebulization and spray-as-you-go topical local anaesthesia of the airway. Br J Anaesth