Anesthesia stages

List and briefly describe the four stages of general anesthesia. 

With newer dragp and techniques, the stages of anesthesia may not be as prominent as those described in Display 35-1. In addition, movement through the first two stages is usually very rapid. 

Induction is a part of stage I anesthesia. It begins with the administration of an anestheticdrug and lasts until consciousness is lost. With some induction drugs, such as the short-acting barbiturates, this stage may last only 5 to 10 seconds. 

Stage IV is the stage of respiratory paralysis and is a rare and dangerous stage of anesthesia. At this stage, respiratory arrest and cessation of all vital signs may occur. 

Albrecht J, Hilgier W, Zielinska M, Januszewski S, Hesselink M, et al. 2000. Extracellular concentrations of taurine, glutamate, and aspartate in the cerebral cortex of rats at the asymptomatic stage of thioacetamide-induced hepatic failure modulation by ketamine anesthesia. Neurochem Res 25(11) 1497-1502. 

IV. Stage of medullary depression This deep stage of anesthesia includes severe depression of the CNS, including the vasomotor center in the medulla, as well as the respiratory center in the brain stem. Without circulatory and respiratory support, death rapidly ensues. 

Stage III. Surgical Anesthesia. As the name implies, this level is desirable for the surgical procedure and begins with the onset of regular, deep respiration. Some sources subdivide this stage into several planes, according to respiration rate and reflex activity.39... 

Stage IV. Medullary Paralysis. This stage is marked by the cessation of spontaneous respiration because respiratory control centers located in the medulla oblongata are inhibited by excessive anesthesia. The ability of the medullary vasomotor center to regulate blood pressure is also affected, and cardiovascular collapse ensues. If this stage is inadvertently reached during anesthesia, respiratory and circulatory support must be provided or the patient will die.39... 

III. Stage of Surgical Anesthesia This stage begins with the recurrence of regular respiration... 

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