[Perioperative management of a case of myasthenic crisis with unexpected difficult airway]

Myasthenia gravis (MG) is an autoimmune disorder characterized by loss of acetylcholine receptors (AChR) due primarily to the production of anti-AChR autoantibodies. We report here a case of anesthetic management of MG patient associated with difficult airway. A 58-year-old woman, 150 cm in height and 43 kg in weight, was scheduled for elective thymectomy. Preoperative evaluation using Mallampati classification, mouth opening, and thyromental distance did not predict airway difficulty. After anesthetic induction with propofol and sevoflurane, mask ventilation was performed easily. However, tracheal intubation using Macintosh type laryngoscope was unexpectedly difficult. This was largely due to transformation of the epiglottis and thereby Cormack classification was grade III. Tracheal intubation was eventually performed by blindly with a gum elastic bougie after some trials. Postoperative day two, she was diagnosed as postoperative myasthenic crisis and needed re-intubation. We used fiberscope intubation for her because it was difficult to intubate."Cannot intubate, cannot ventilate (CICV)" scenario is very rare, but it sometimes leads to serious morbidity and mortality. Therefore, we need to deal with this emergency situation by using a variety of equipments and techniques. Careful examination of the airway and a carefully considered plan for re-intubation are prerequisites for this type of surgery.