We read with great interest the recent article by Malcharek et al.1 comparing the efficacy of two airway topical anaesthesia techniques for awake fibreoptic intubation in patients at risk of secondary cervical injury. They showed that awake fibreoptic intubation using the translaryngeal injection technique was faster and produced less cough or gagging compared with that using the Enk Fibreoptic Atomizer (COOK Medical Europe Ltd., Limerick, Ireland). Given that adequate airway topical anaesthesia is an important prerequisite to ensure successful awake fibreoptic intubation and patient comfort,2 their findings have potential implications. We congratulate the authors for conducting this clinically useful research, but would like to ask some questions about their methodology.
First, awake fibreoptic intubation includes two parts, airway topical anaesthesia and then subsequent intubation.3 A limitation of this study design is the lack of evaluation of patient comfort during topical anaesthesia of the airway. It is generally believed that translaryngeal application of local anaesthetics often incites powerful coughing and patient discomfort. Furthermore, local anaesthetic injected into the airway is nebulised and distributed over the infraglottic and supraglottic structures by the patient's coughing.2 In contrast, airway spray of a local anaesthetic with a fibreoptic bronchoscope using a ‘spray-as-you-go’ technique produces only low levels of discomfort for patients.4
Second, a 1-min waiting period after lidocaine application ensured that the local anaesthetic had an effect on the airway mucosa. In fact, as with other local anaesthesia methods, ‘tincture of time’ is one of the most useful supplements to airway topical anaesthesia.5 Although 2 to 4% lidocaine applied to the airway mucosa begins to produce topical anaesthesia after about 1 min, 3 to 5 min of contact time is usually required to provide adequate penetration of lidocaine into the airway mucosa to achieve a maximal effect.6 In this study, 18 and 31% of patients in the translaryngeal injection and the Enk Fibreoptic Atomizer groups, respectively, had a coughing score 3 or 4 during awake fibreoptic intubation, and the percentages with a gagging score 3 or 4 were 22 and 24%, respectively. We argue that inadequate airway topical anaesthesia because of an inadequate waiting time for the maximal effect of lidocaine may explain such high incidences of patient discomfort.
Third, the patients were interviewed on the first postoperative day and were asked to rank postoperative sore throat using a visual analogue scale ranging from 1 to 5. When postoperative sore throat is compared between groups, standardization of postoperative analgesia should be a crucial component of the study design. The type and dose of analgesia and the timing of its administration in relation to the assessment of postoperative sore throat should have been described in the ‘Methods’ section. Because it is not possible to compare postoperative analgesia in the two groups, the secondary outcome findings and their subsequent conclusions should be interpreted with caution, as they may have been determined using incomplete methodology.7
Finally, the level of sedation was determined after awake fibreoptic intubation but before anaesthesia induction using a modified Ramsay scoring system ranging from 1 to 4. We noted that 64 to 70% of patients had a modified Ramsay score 1. This sedation depth seems insufficient for awake fibreoptic intubation. To ensure the comfort of awake patients and successful instrumentation, we believe that before awake fibreoptic intubation is started the level of sedation required if using the modified Ramsay score should be 2 (awake, eyes closed).8,9
Acknowledgements related to this article
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Comment from the editor: Dr Malcharek did not respond to our invitation to submit a reply to this letter.
1. Malcharek MJ, Bartz M, Rogos B, et al. Comparison of Enk Fibreoptic Atomizer with translaryngeal injection for topicalanaesthesia for awake fibreoptic intubation in patients at risk of secondary cervical injury: a randomised controlled trial. Eur J Anaesthesiol
2. Simmons ST, Schleich AR. Airway regional anesthesia for awake fiberoptic intubation. Reg Anesth Pain Med
3. Kundra P, Kutralam S, Ravishankar M. Local anaesthesia for awake fibreoptic nasotracheal intubation. Acta Anaesthesiol Scand
4. Xue FS, Liu HP, He N, et al. Spray-as-you-go airway topical anesthesia in patients with a difficult airway: a randomized, double-blind comparison of 2% and 4% lidocaine. Anesth Analg
5. Stackhouse RA. Fiberoptic airway management. Anesthesiol Clin North Am
6. Morris IR. Pharmacologic aids to intubation and the rapid sequence induction. Emerg Med Clin North Am
7. Xue FS, Xiong J, Wang Q, et al. Comparison of safety and efficacy of Supreme laryngeal mask airway and ProSeal laryngeal mask airway. Eur J Anaesthesiol
8. Eftekharian HR, Zarei K, Arabion HR, et al. Remifentanil, ketamine, and propofol in awake nasotracheal fiberoptic intubation in temporomandibular joint ankylosis surgery. J Craniofac Surg
9. Rosenstock CV, Th⊘gersen B, Afshari A, et al. Awake fiberoptic or awake video laryngoscopic tracheal intubation in patients with anticipated difficult airway management: a randomized clinical trial. Anesthesiology