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by Eugenie Heitmiller, MD

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Heitmiller, Eugenie. "How Anesthesia Works." 01 April 2000. HowStuffWorks.com. <http://health.howstuffworks.com/anesthesia.htm> 19 July 2008.

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Local Anesthesia

Local anesthesia involves numbing a small area by injecting a local anesthetic under the skin just where an incision is to be made. When used alone, this type of anesthesia has the least number of risks. Local anesthetics are thought to block nerve impulses by decreasing the permeability of nerve membranes to sodium ions. There are many different local anesthetics that differ in absorption, toxicity, and duration of action.

Photo courtesy Department of Defense: Defense Visual Information Center
Captain Cynthia Warwick (right) and Staff Sergeant Chad Smith, U.S. Air Force, prepare a syringe with local anesthesia during Operation Enduring Freedom.

One of the most commonly used local anesthetics is lidocaine (Xylocaine). Lidocaine can be administered as an injection or placed topically on mucous membranes. Another topical anesthetic is cocaine. Cocaine is primarily used to anesthetize the nasal passages for surgical procedures. A topical anesthetic that is gaining popularity for anesthetizing the skin prior to painful procedures, such as injections, is known as eutectic mixture of local anesthetics (EMLA) cream which contains lidocaine and prilocaine. This white cream is placed on the skin and then covered with an occlusive dressing for approximately one hour to obtain a good numbing effect. In addition, EMLA can be used to numb the skin prior to giving injections or pulling superficial splinters.

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