A 52-year-old man is undergoing general anesthesia for an open abdominal surgery. During induction with propofol, the anesthesiologist observes that the patient progresses through the classical stages of anesthesia. At the point where the patient exhibits nystagmus, irregular breathing with periods of apnea, and loss of corneal reflex, which stage of anesthesia is the patient in, and what is the primary concern during this stage?