During which stage of anesthesia does respiration stop and cardiac arrest occur?

Stage IV of anesthesia is characterized by the most profound level of unconsciousness and significant respiratory and cardiovascular depression. During this stage, respiration often ceases altogether, and cardiac arrest is a critical risk due to the deep suppression of central nervous system function. This stage represents the point where the patient is no longer able to maintain the basic physiological processes necessary for survival without assistance.

In contrast, Stage III, which includes the surgical anesthesia phase, allows for controlled breathing and cardiovascular stability, while Stage II is marked by excitement and struggling, where the patient is still able to breathe on their own. Light Stage III represents an early level of surgical anesthesia where the patient may still maintain some physiological stability. Thus, Stage IV is distinct in its severity, highlighting the importance of monitoring and intervention during anesthesia to prevent the patient from progressing into this dangerous stage.