[Anesthetic management of a patient with postthymectomy myasthenia gravis]

A 56-year-old male who had received total thymectomy for treatment of myasthenia gravis was scheduled for sigmoidectomy under general anesthesia. Since his symptoms had become worse after the thymectomy along with increased anti-acetylcholine receptor antibody titer, preoperatively we could not estimate his sensitivity to non-depolarizing muscle relaxants. We initially tried tracheal intubation without using a non-depolarizing muscle relaxant immediately after intravenous injection of propofol 2 mg.kg-1 and fentanyl 4 micrograms.kg-1. Since the intubation was unsuccessful, however, vecuronium 0.01 mg.kg-1 was repeatedly administered until TOF ratio reached 0%. Successful intubation was performed with 3.5 mg of vecuronium. We conclude that the initial trial of tracheal intubation should be performed without a non-depolarizing muscle relaxant in patients with myasthenia gravis whose symptoms have become worse after thymectomy. If first attempt is unsuccessful, the tracheal intubation should be performed with a smaller dose of vecuronium using an electrical nerve stimulator.