Several earlier reports have described life-threatening airway obstruction during arthroscopic shoulder surgery performed under regional anesthesia, caused by the leakage of irrigation fluid out of the shoulder joint space into the surrounding soft tissues and then the neck and the pharynx. Here, we present a case of airway obstruction that occurred in a patient under general anesthesia. A 77-year-old woman with a rotator cuff rupture who was to undergo right-shoulder arthroscopic surgery was anesthetized with fentanyl and propofol. Her airway was secured with a flexible laryngeal mask airway (LMA). During surgery, the compliance of her breathing bag became gradually poorer, and finally we were not able to ventilate her at an airway pressure of 60 cmH2O. We found that her chest wall, neck, and face were swollen and tense. Laryngoscopy revealed massive swelling of the pharyngeal soft tissues. The vocal cords were not visible. Her trachea was intubated blindly, and adequate ventilation was re-established. She was placed in the Fowler position and furosemide was given intravenously. Her neck and chest swelling were reduced over the next 2 h and she was extubated without any problem. We recommend that physicians should periodically examine the neck of any patient undergoing arthroscopic shoulder surgery, especially when general anesthesia is used, because anesthetized patients cannot complain of breathing difficulty and the airway swelling may progress until it becomes life-threatening.