General anesthesia stages

List and briefly describe the four stages of general anesthesia. 

A 26-year-old woman in the second stage of labor received an infusion of oxytocin 10 U/l in 5% dextrose at a variable rate of 10-150 ml/ hour. In the 5 hours after delivery, which was complicated by a retained placenta requiring general anesthesia for removal, she received isotonic fluid 5500 ml, 5% dextrose 3500 ml with oxytocin 50 U/l, hydroxyethyl starch 1000 ml, and 4 units of blood. She then received 5% dextrose 7500 ml with oxytocin 100 U/l over 15 hours 24 hours later her serum sodium concentration was 113 mmol/l. She became unconscious and had a generalized convulsion. She subsequently made a full recovery. 

The stage of anesthesia not reached by the patient is medullary paralysis. The respiratory center (medulla oblongata) becomes paralyzed. Breathing and vital functions cease. Death occurs. However, the anesthetist adjusts the general anesthetic to prevent the patient from reaching this stage. 

The action of toxic doses of atropine is observed on the central nervous system. There is a functional alteration of the brain as well as lower regions of the nervous system. There is neither an increase nor decrease of the reflexes except in the last stages corresponding to the coma, anesthesia, and profound depression of the brain. The bulbar respiratory center is stimulated, the respiration being increased in rate and amplitude during the stage of central stimulation. Cushny (120) stated that it is not known whether there is a direct action on the center or an indirect effect due to the products of metabolism such as carbon dioxide. But even small doses which cause no general excitation provoke a respiratory stimulation which makes it probable that there exists a direct action on the bulbar respiratory center (119). 

Mrs. R. was admitted to labor and delivery and a normal spontaneous vaginal delivery was anticipated. Her first stage of labor was uneventful. She refused epidural anesthesia and reached full dilatation 4 hours after admission. During this phase of labor, her muscular back pain was treated with gentle myofascial stretching techniques. In general, obstetric patients in active labor tolerate these types of soft tissue techniques. However, as labor pain intensifies, patients may be unable to bear any manipulative treatment. This patient expressed relief of her muscular back pain but was unable to endure treatment of the sacrum and iliopsoas because of labor pain. 

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