Why is stage IV of general anesthesia dangerous?

Stage IV of general anesthesia is considered dangerous because it represents an overdose of the anesthetic agent, characterized by the loss of spontaneous respiration and the imminent collapse of cardiovascular control.1

While general anesthesia is divided into four stages to monitor the depression of the brain’s sensory responsiveness, stage IV indicates that the patient has reached a critical level of physiological depression where vital life-sustaining functions are failing. Physicians aim to maintain patients within stage III, which is the level of full surgical anesthesia, to ensure safety while performing medical procedures.1