The different stages of anesthesia are:
Stage I: Analgesia and conscious sedation
Stage II: Stage of delirium
Stage III: Stage of Surgical Anesthesia
Plane I: Pupils dilate progressively with the depth of anesthesia. Lid reflex, swallowing, retching and vomitting gets abolished. Corneal reflex is present. Conjunctival reflex is absent. Pharyngeal reflex is lost.
Plane II: Eye balls fixed, laryngeal reflexes are also abolished.
Plane III: Asynchrony between thoracic and abdominal movements. Progressive paralysis of intercostal muscles, Pupillary light reflex and corneal reflex are lost.
Plane IV: Complete intercostal muscle paralysis. Pupils are dilated. Muscles are flaccid.
Stage IV: Stage of respiratory paralysis
Minor surgeries like dental extractions are carried out in stage I or stage of analgesia. Major surgeries are carried out on Plane III of Stage III of General Anesthesia or the stage of Surgical Anesthesia.