Topic Overview

General anesthesia is a combination of medicines that you inhale through a mask or receive through a needle in a vein to cause you to become unconscious. It affects your whole body. Under anesthesia, you should be completely unaware and not feel pain during the surgery or procedure. General anesthesia also causes forgetfulness (amnesia) and relaxation of the muscles throughout your body.

General anesthesia suppresses many of your body’s normal automatic functions, such as those that control breathing, heartbeat, circulation of the blood (such as blood pressure), movements of the digestive system, and throat reflexes such as swallowing, coughing, or gagging that prevent foreign material from being inhaled into your lungs (aspiration).

Because these functions are suppressed, an anesthesia specialist must carefully keep a balance of medicines while watching your heart, breathing, blood pressure, and other vital functions. An endotracheal (ET) tube or a laryngeal mask airway device is usually used to give you an inhaled anesthetic and oxygen, and to control and assist your breathing.

General anesthesia is commonly begun (induced) with intravenous (IV) anesthetics. But inhaled anesthetics also may be used. After you are unconscious, anesthesia may be maintained with an inhaled anesthetic alone, with a combination of intravenous anesthetics, or a combination of inhaled and intravenous anesthetics.

As you begin to awaken from general anesthesia, you may experience some confusion, disorientation, or difficulty thinking clearly. This is normal. It may take some time before the effects of the anesthesia are completely gone.

Risks and complications from general anesthesia

Serious side effects of general anesthesia are uncommon in people who are otherwise healthy. But because general anesthesia affects the whole body, it is more likely to cause side effects than local or regional anesthesia. Fortunately, most side effects of general anesthesia are minor and can be easily managed.

General anesthesia suppresses the normal throat reflexes that prevent aspiration, such as swallowing, coughing, or gagging. Aspiration occurs when an object or liquid is inhaled into the respiratory tract (the windpipe or the lungs). To help prevent aspiration, an ET tube may be inserted during general anesthesia. When the tube is in place, the lungs are protected so stomach contents cannot enter the lungs. Aspiration during anesthesia and surgery is very uncommon. To reduce this risk, people are usually instructed not to eat or drink anything for a certain number of hours before anesthesia so that the stomach is empty. Anesthesia specialists use many safety measures to minimize the risk of aspiration.

Insertion or removal of an ET tube or other airway device may cause respiratory problems such as coughing or gagging. Insertion of an airway device also may cause an increase in blood pressure (hypertension) and heart rate (tachycardia). Other complications may include damage to teeth and lips, swelling in the larynx, sore throat, and hoarseness caused by injury or irritation of the larynx.

Nausea and vomiting are more likely with a lengthy procedure and also with certain types of procedures, such as eye or abdominal surgery. In most cases, nausea after anesthesia doesn't last long and can be treated with medicines called antiemetics. Vomiting may be a serious problem if it causes pain and stress or affects surgical incisions.

Other serious risks of general anesthesia include changes in blood pressure or heart rate or rhythm, heart attack, or stroke. Death or serious illness or injury due solely to anesthesia is rare and is usually also related to complications from the surgery.

Some people who are going to have general anesthesia express concern that they will not be completely unconscious but will "wake up" and have some awareness during the surgical procedure. But awareness during general anesthesia is very rare. Anesthesia specialists devote careful attention and use many methods to prevent this.