General anesthesia is a combination of medications that a person inhales through a mask or receives through a needle in a vein to cause the person to become unconscious. General anesthesia affects the whole body, including the brain, heart, and lungs, and therefore increases a person's risk of side effects, most of which are minor and can be easily managed.

Rare but serious risks of general anesthesia include:

• Irregular heartbeat (arrhythmia).
• Increases or decreases in blood pressure, which may be dangerous.
• A rapid increase in body temperature.
• Rare reactions to medications used in the anesthesia.
• Difficulty breathing.
• Heart attack or stroke.
• Death from complications of changes in heartbeat, blood pressure, body temperature, or breathing.

Serious side effects of anesthesia are uncommon, especially in people who are otherwise generally healthy. Anyone who has medical problems, such as heart, lung, kidney, or endocrine conditions, including diabetes, should tell the person who will be giving the anesthesia (the anesthesiologist or nurse anesthetist). Also, a person should report any medications he or she is taking and whether he or she has any allergies.