A 58-year-old man is undergoing emergency repair of a perforated peptic ulcer under general anesthesia. Five minutes after induction with thiopental, the anesthesiologist observes the following: the patient has irregular, gasping respiration; blood pressure is 160/95 mmHg; heart rate is 110 bpm; there is vigorous thrashing and involuntary limb movement; the eyes are open with dilated pupils; and there is active vomiting. The patient has not yet been intubated. What is the current anesthetic stage, and what is the most appropriate immediate action?