Discussion
General recommendations for difficult airway management are awake fiberoptic intubation, awake video laryngoscope, laryngeal mask airway as an intubating conduit, lightwand, oral or nasal blind intubation, retrograde intubation, invasive airway access, and ECMO which is left as the last method [9]. In this case, due to the severe contractures and microstomia, direct visualization of the pharynx and larynx by video laryngoscope seemed impossible. Laryngeal mask airway was not considered because size # 3 or 4 for a female adult is too large to pass through her mouth. Orotracheal intubation with lightwand was excluded on the reason that neck scars cannot be illuminated. Retrograde intubation and tracheostomy were also excluded for the reason that anterior neck structures, including the larynx, trachea, and carotid arteries, are unidentifiable and impalpable. For the distortion of the upper airway and uncertainty of success, oral or nasal blind intubation was not the preferred choice. Due to a good safety and success profile, awake fiberoptic intubation is a preferred choice of anticipated difficult tracheal intubation [3]. However, ATI may give patients significant discomfort and nociceptive recall [10-12] or be perceived as potentially dangerous when causing a pronounced sympathetic response [13]. Furthermore, due to the several failures of awake intubation in other medical centers, the patient refused to accept it again. Therefore, fiberoptic intubation with precise sedation, analgesia, and without inhibition of spontaneous ventilation and cardiovascular function seems an ideal choice.
At present, many sedative drugs, such as midazolam, dexmedetomidine, propofol, sevoflurane, can be selected. A low dose of midazolam produces a direct amnesia effect. Dexmedetomidine provides a good sedative effect in awake conditions, but the sedation needs to be carefully titrated as excessive sedation can lead to hypoventilation and bradycardia, or inadequate sedation leads to discomfort, anxiety and excessive sympathetic discharge. Moreover, dexmedetomidine may cause nociceptive recall [8, 14]. Compared with propofol intravenous anesthesia, sevoflurane inhalational has less effect on respiratory depression [13]. Moreover, sevoflurane can be quickly washed out. Thus, it is more controllable than other intravenous drugs. In this case, midazolam 2 mg, sufentanil 5 μg, and intermittent sevoflurane inhalation were administrated to provide precise sedation and analgesia. Meanwhile, an oral hose was connected to a high flow of oxygen to prevent hypoxia. However, sedation should not be used as a substitute for inadequate airway topicalization [3].
To sufficiently anesthetize the upper airway and suppress the gag, swallow and cough reflexes, a perfect topicalization is essential. There are many ways of airway topicalization, such as nebulization with lidocaine, nerve block, thyrocricocentesis spraying, and the SAYGO technique [2]. However, research indicated that atomization of local anesthetics had a potential possibility of higher stress responses and poisoning [15]. Due to anatomical structure changes, nerve block and thyrocricocentesis were impossible for such kind of patients. Compared with the classical SAYGO technique that lidocaine sprayed directly via the working channel of the fiberscope, the modified SAYGO technique, which lidocaine sprayed via an epidural catheter inserted through the working channel of the fiberscope, controls the dosage of local anesthetics more accurately and does a better anesthesia effect, therefore usually used in patients with difficult airway [6-8]. However, the epidural catheter does not match with all fiberscopes. Here, we directly fastened the epidural catheter at the end of the fiberscope. Moreover, this SAYGO technique can evaluate the airway passage directly, which increases the safety of intubation. Thus, it seemed a better choice in this case.
Furthermore, once the local anesthetics worked, the patient was sedated by sevoflurane inhalation again, then intubated by the guidance of flexible bronchoscopy. Taken together, using intermittent sevoflurane inhalation and the modified SAYGO technique, a safe, comfortable, unconscious, and satisfied intubation with spontaneous breathing keeping was achieved in a postburn patient with severe difficult airway and unwillingness to accept ATI. Moreover, this strategy is not limit to postburn patients with difficult airway.