Anesthesia is the process by which feeling is removed or blocked to alleviate or prevent pain. Surgery and other medical procedures that require a patient to remain still and calm are most often the reason for anesthesia. How anesthesia affects a body typically depends on the procedure, the type of medications used and the patient's general health.
Types of Anesthesia
Local anesthesia involves injecting a drug into a specific part of the body. It blocks the electrical impulses that nerves generate. The nerves still register pain, but the "ouch" signal does not reach the brain. The injected chemical blocks the sodium channels in the nerve. There is also regional anesthesia, which is simply a local anesthetic writ large. It prevents the transmission of chemical receptors over a much larger area, and entire nerve clusters can be blocked in this way. Regional and local anesthesia do not effect the brain directly, but individual nerve endings instead. Sedation is a more broad-spectrum anesthetic, and patients are given a chemical cocktail to make them sleepy. They are not rendered unconscious, but in order to be the most comfortable for some invasive procedures such neurological or abdominal surgery the patient may be taken to the very edge of unconsciousness. This level of anesthesia requires close monitoring from a qualified anesthesiologist in order to ensure the safety of the patient. Sedatives are introduced directly to the bloodstream so the level of medication can be kept constant. Sedation drugs affect the brain directly, as well, and higher doses are often used for general anesthesia and total unconsciousness.
General Anesthesia
With general anesthesia, medication directly affects the brain, leading to a state of total unconsciousness. The patient's nerves still register pain, and the brain still registers the pain. But the patient's unconscious state causes him to feel no pain while he is under the influence of the anesthetic. The mechanics of general anesthesia remains largely a mystery. It partially works by relaxing muscles and slowing the functions of the brain itself.
