And to complicate the discussion even more, most general anesthetics consist of several different agents used in various proportions. A typical general anesthetic includes such agents as inhalational agents (anesthesia gases), hypnotic agents (major tranquilizers), muscle relaxing drugs, and narcotics (pain medications). General anesthetics often include an example from each of these categories, but not always. The choices are influenced by the nature of the surgical operation, the physical condition of the patient, availability, and the preferences of the anesthesia providers.

A common scenario for the administration of general anesthesia in an adult would be first to establish an intravenous infusion, or IV; often a small dose of an anxiolytic (anxiety-relieving) drug can be given intravenously to help calm the patient prior to transfer to the operating room. While these agents do not usually produce unconsciousness, they typically do induce amnesia (memory loss) of events that occur while patients are under their influence. Often patients have no memory of even going to the operating room.

However, the full anesthetic is not begun until after the patient has arrived in the operating room. Once there, a variety of monitoring devices are applied, such as EKG, blood pressure cuff, pulse oximeter (which measures the amount of oxygen in the patient's blood), stethoscopes, etc. Other monitoring modalities may be instituted depending on the nature of the operation and the physical status of the patient.

When the surgeon is ready for the patient to be anesthetized, the anesthetic induction is begun. For adults, this is usually accomplished with a series of medication is given through the IV. These medications are referred to as induction agents, so named because they induce or bring about the state of anesthesia. For small children, in whom establishing IV access can be more difficult while awake, anesthesia is often induced by administering inhalational agents, or gases, by means of a mask placed over the mouth and nose. If needed, the IV is then placed after the child is asleep. Although the induction agents begin the anesthetic, they are not usually all that is used. Their value is in quickly establishing the anesthetized state. Most of these agents are fairly short-acting, however; if nothing else were given the patient would probably be awake again before the surgery had even started!

Induction agents are frequently used to anesthetize the patient for what is called endotracheal intubation. This is the act of placing a breathing tube, usually through the mouth, past the vocal cords and into the trachea, or windpipe. Once this has been accomplished, longer-acting agents are given IV and anesthesia gases may be administered through the tube. The reason why short-acting induction agents are used for the breathing tube placement is that occasionally unanticipated difficulty is met in achieving correct tube placement. This is usually due to diseases of, or variations in the anatomy of, the patient's throat, larynx, jaws, or neck. When problems arise, it's advantageous to have used drugs that will wear off soon and allow the patient's body to return to its normal functions while the situation is reassessed.

After proper tube placement, the anesthesia for the surgery is begun. Typically this consists of inhalational agents delivered through the breathing tube plus narcotic and muscle-relaxing drugs given IV. Each agent plays its own role in producing anesthesia. The inhalational agents, or gases, seem to affect the membranes of nerve cells. They appear to reduce nerve cell activity and thus decrease awareness and memory; narcotics blunt the perception of pain; and muscle relaxants, though not always required, are often used to facilitate the surgery by making it easier for the surgeon to separate muscle layers and gain the needed exposure. By the way, these muscle relaxants aren't selective in the muscles they work on; they weaken all the muscles of the body, including the muscles used for breathing, and this is one of the reasons a breathing tube is used: it allows a good means of assisting respirations under anesthesia. In fact, most people are placed on a ventilator (breathing machine) while they are under anesthesia if muscle relaxants are used.

The anesthesia is continued in this manner until the completion of surgery, at which time the gases are discontinued and if necessary the effects of the muscle relaxants are antagonized or "reversed" with IV medications. When the patient has regained sufficient strength and responsiveness, the breathing tube is removed and the patient is transferred to the recovery room for monitoring. Most persons are awake enough to be responsive and cooperative soon after arrival in recovery, although their memory of events may lag behind somewhat. Most people associate the moment that their memory returned with "waking up" although usually they were to all outward appearances awake before that time.

There are several approaches to the delivery of anesthesia. At CAA we practice using the Anesthesia Care Team approach. This has proven an effective mode of anesthesia delivery for CAA since our inception in 1972.