Anesthesia, or anaesthesia (from Greek αν-, an-, "without"; and αἴσθησις, aisthēsis, "sensation"), traditionally meant the condition of having sensation (including the feeling of pain) blocked or temporarily taken away. It is a pharmacologically induced and reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes, decreased stress response, or all of these simultaneously. These effects can be obtained from a single drug which alone provides the correct combination of effects, or occasionally a combination of drugs (such as hypnotics, sedatives, paralytics and analgesics) to achieve very specific combinations of results. This allows patients to undergo surgery and other procedures without the distress and pain they would otherwise experience. An alternative definition is a "reversible lack of awareness," including a total lack of awareness (e.g. a general anesthetic) or a lack of awareness of a part of the body such as a spinal anesthetic. The pre-existing word anesthesia was suggested by Oliver Wendell Holmes, Sr. in 1846 as a word to use to describe this state.
Types of anesthesia include local anesthesia, regional anesthesia, general anesthesia, and dissociative anesthesia. Local anesthesia inhibits sensory perception within a specific location on the body, such as a tooth or the urinary bladder. Regional anesthesia renders a larger area of the body insensate by blocking transmission of nerve impulses between a part of the body and the spinal cord. Two frequently used types of regional anesthesia are spinal anesthesia and epidural anesthesia. General anesthesia refers to inhibition of sensory, motor and sympathetic nerve transmission at the level of the brain, resulting in unconsciousness and lack of sensation. Dissociative anesthesia uses agents that inhibit transmission of nerve impulses between higher centers of the brain (such as the cerebral cortex) and the lower centers, such as those found within the limbic system.
If you are having surgery, your doctor will give you a drug called an anesthetic. Anesthetics reduce or prevent pain. There are four main types.
- Local: numbs one small area of the body. You stay awake and alert.
- Conscious or intravenous (IV) sedation: uses a mild sedative to relax you and pain medicine to relieve pain. You stay awake but may not remember the procedure afterwards.
- Regional anesthesia: blocks pain in an area of the body, such an arm or leg. Epidural anesthesia, which is sometimes used during childbirth, is a type of regional anesthesia.
- General anesthesia: affects your whole body. You go to sleep and feel nothing. You have no memory of the procedure afterwards.
The type of anesthesia your doctor chooses depends on many factors. These include the procedure you are having and your current health.