A 20-year-old man without significant prior medical or surgical history presents for tonsillectomy. Induction of anesthesia is achieved with thiopental, fentanyl, and suc-cinylcholine. Anesthesia is maintained with nitrous oxide 70%, oxygen 30%, and isoflurane 1%. Fifteen minutes into the procedure, his blood pressure rises to 190/100 mmHg, and the heart rate increases to 130 beats per minute. The mass spectrometer shows an end-tidal carbon dioxide (ETCO2) concentration of 60 mmHg, despite a minute ventilation of 110 mL/kg/minute.