International Journal of Surgery and Anesthesia Research

Stages of Anaesthesia

There are four stages of general anesthesia that help providers to better predict the course of events, from anesthesia induction to emergence. Stage I begins with the induction of anesthesia and ends with the patient's loss of consciousness. The patient still feels pain in Stage I. Stage II, or REM stage, includes uninhibited and sometimes dangerous responses to stimuli, including vomiting and uncontrolled movement. This stage is typically shortened by administering a barbiturate, such as sodium pentothal, before the anesthetic agent. Stage III, or surgical anesthesia, is the stage in which the patient's pupillary gaze is central and the pupils are constricted. This is the target depth of surgical anesthesia. During this stage, the skeletal muscles relax, the patient's breathing becomes regular, and eye movements stop. Stage IV, or overdose, is marked by hypotension or circulatory failure. Death may result if the patient cannot be revived quickly.

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