There are three major types of anesthesia used today. The first and most common is a general anesthesia. This is a state of being in a rug induced coma like state, commonly caused by nitrous oxide. This state of sleep is classified by what are called the four A’s. These A’s are analgesia, amnesia, anesthesia, and akinesia, which mean the absence of pain, loss of retentive memory, unconsciousness, and motor loss. Twilight anesthesia, another type, is extremely similar to a general anesthesia. This anesthetic is given in monitored amounts in order to allow for light to heavy sedation of the patient, while still allowing the patient to remain conscious. The third type of anesthetics is regional anesthetics, sometimes called spinal or epidural anesthetics. This anesthetic is administered to and remains in a limited amount of the body, and allows the receiver to remain alert during a procedure but not feel the pain. Each anesthesia has its benefits and depending on the type of procedure, the anesthesia administer will choose the ideal anesthetic.