EDITOR:
Anaesthesiologists still face severe airway disasters that may lead to permanent disability and even death. Numerous guidelines for difficult airway management have been developed, along with a wide range of techniques [1,Reference Handerson, Popat, Lato and Pearse2]. The incidence of difficult intubation has been reported to range from 1% to 18% [Reference Benumof3,Reference Tse, Rimm and Hussain4]. The incidence of ‘cannot intubate’ was found to be around 0.05–0.35% [Reference Handerson, Popat, Lato and Pearse2,Reference Cormack and Lehane5], whereas that of ‘cannot intubate–cannot ventilate’ situation was around 0.0001–0.02% [Reference Benumof6]. We present a case of unrecognized difficult airway with a ‘cannot intubate–cannot ventilate’ scenario due to a rare malformation of the upper airway.
Case report
A 43-yr-old ASA I male suffering from chronic low-back pain was admitted for an elective lumbar discectomy. The preoperative anaesthetic assessment revealed a healthy male with no history of allergies or general anaesthesia in the past. Airway examination revealed a neck with free movements (extension and flexion), normal mouth opening (more than 6 cm), an inter-incisor width of 7 cm, class II pharyngeal landmarks in the Samson and Young classification and a thyromental distance greater than 6 cm.
General anaesthesia was induced with midazolam, remifentanil, propofol and rocuronium to facilitate endotracheal intubation. Ventilation by facemask encountered some difficulty but oxygen saturation was maintained within the normal range. Direct laryngoscopy revealed an oblique plane of the epiglottis corresponding to a laryngoscopic view grade III. The anaesthesiologist improved the position by placing another pillow under the shoulders and performed the optimal external laryngeal manipulation manoeuvre. The first and second attempts to insert an endotracheal tube failed and the anaesthesiologist called for assistance. Upon the arrival of a second senior anaesthesiologist, mask ventilation proved very difficult, despite the two-person mask ventilation. A laryngeal mask failed to provide effective ventilation. An intubating laryngeal mask airway was inserted at this point in an attempt to facilitate tracheal intubation but ventilation by this technique was poor and tracheal intubation failed. The laryngeal mask was removed. The mask ventilation was becoming more and more difficult, with oxygen saturation decreasing and the patient becoming bradycardic. At this stage, the anaesthesiology staff attempted to perform transtracheal jet ventilation, yet three repeated attempts failed. In the meantime, the ENT surgeons had been urgently called. Surgical cricothyroidotomy was started by the anaesthesiologists pending the arrival of the ENT team, but it failed as well. Maintaining oxygenation by mask ventilation was extremely difficult throughout these manipulations. The otolaryngologists encountered serious problems but succeeded eventually in obtaining a definitive airway by tracheotomy. The patient began to breathe spontaneously. Sedation, analgesia and muscle relaxation were next administered and the patient was transferred to the ICU for mechanical ventilation and observation without undergoing surgery.
A computerized tomography scan of the neck and upper airway performed on the second day revealed severe malformations, i.e. a low-lying valleculae at the level of C5–C6 (instead of C3 normally) – with the tracheotomy cannula penetrating through them, a low epiglottis, and an asymmetrical larynx with an obliterated left piriform sinus. We also noted a very low position of the hyoid bone at the C7 level (instead of C3–C4), which was obliquely positioned, with the hyoid cornua on the right lying higher than the one on the left, probably as a result of dislocation. Furthermore, a laterally rotated and low-lying thyroid cartilage was found at T1 (instead of C5), as well as a vertical oblique position of the vocal cords (instead of the normal horizontal orientation) that were lying at the level of the apex of the lungs. The trachea was short (8.5 cm instead of 10–12 cm in the normal adult male). A computerized tomography image of the malformed airway is presented in Figure 1.
Computerized tomography image of the malformed airway.
The hypnotic medications and relaxants were stopped on the third day and the patient regained full consciousness. After a short course of weaning from mechanical ventilation, he was able to maintain normal oxygenation and ventilation by an oxygen mask. Neurological examination proved normal and the patient was transferred on day 4 to the ENT department for observation and further management. The tracheostomy tube was removed and the tracheotomy closed. The patient was discharged fully recovered on day 18, with a Medical Alert wallet card giving details of his difficult airway.
Discussion
Difficult tracheal intubation remains the most crucial predicament anaesthesiologists ever encounter in the operating room. The unanticipated difficult airway is a clinical problem encountered by most anaesthesiologists at some point, and is probably the most important cause of major anaesthesia-related morbidity [Reference Cheney and Weiskopf7]. Despite the development of various innovative devices for ventilation/intubation as well as the numerous alternative techniques for unanticipated difficult ventilation or tracheal intubation, studies designed to assess the efficacy of a predefined algorithm in the case of an unanticipated difficult airway are few [Reference Dimitriou, Voyagis and Brimacombe8,Reference Parmet, Colonna-Romano, Horrow, Miller, Gonzales and Roenberg9]. Parmet and colleagues [Reference Parmet, Colonna-Romano, Horrow, Miller, Gonzales and Roenberg9] reported the systematic use of the laryngeal mask in the case of combined unanticipated difficult intubation and ventilation and demonstrated that 94% of patients treated with the laryngeal mask as the first rescue alternative technique were successfully ventilated. Dimitriou and colleagues [Reference Dimitriou, Voyagis and Brimacombe8] reported a high success rate of tracheal intubation using the intubating laryngeal mask airway in 44 unpredicted failed laryngoscopy-assisted tracheal intubations. Despite following the management pathway according to the ASA guidelines in the present case, all of the orderly attempts to achieve endotracheal intubation failed because of severe malformation of the whole upper airway and the trachea. The lower position of the hyoid bone (mainly the right cornua) had caused a misinterpretation of the thyromental distance during the preoperative airway evaluation.
The presented case describes an unsuspected abnormal anatomy of the airway that extended from the epiglottis to the short and low-lying trachea. This malformation defied the almost normal examination of the patient’s airway (with the exception of the slightly short neck). This case of nearly fatal outcome is a rare case of severe airway malformation with an unknown congenital disorder or an acquired traumatic anomaly as possible aetiologies. With the peculiar laryngeal malformation and the hybrid position of the hyoid bone, this may be the first-described case of its kind. On a practical level, we conclude that one can never be too careful in preoperative anaesthetic assessment. Furthermore, since otolaryngologists are not always present in every instance (e.g. small hospitals, rural settings), we propose that anaesthesiologists become more familiar with surgical airway management by means of seminars and programmed workshops.
