Absence of pain sensation; numbing a tooth is local anesthesia; with general anesthesia the patient is unconscious. There are three different types of anesthesia. These are local regional and general.
Local anesthesia will only produce a numbing sensation and involves numbing a small area by injecting a local anesthetic under the skin just where an incision is to be made. It is used primarily for minor surgery.
The administration of a local anesthesia has the effect of numbing nerves so that they do not allow the 'pain signal' to be sent through the nervous system to the brain. Local anesthetics are thought to block these nerve impulses that produce the pain signal 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.
One of the most commonly used local anesthetics is lidocaine. Lidocaine can be administered as an injection or placed topically on mucous membranes. One common topical anesthetic used for anesthetizing the skin prior to painful procedures is known as eutectic mixture of local anesthetics (EMLA) cream which contains lidocaine and prilocaine another anesthetic. 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.
Regional anesthesia is used for slightly more difficult procedures. Regional anesthesia is used to eliminate pain in a larger part of the body by temporarily blocking large groups of nerves or the spinal cord so that the pain signal cannot reach the brain. Regional anesthesia is so named because a ﾔregionﾔ of the body is anesthetized without making the person unconscious. One example of this is spinal anesthesia which is often used on women during childbirth. A local anesthetic is injected into the spinal fluid and causes a loss of sensation of the lower body. Spinal anesthesia can be used for surgery on the legs or lower abdomen.
Regional anesthesia techniques can be used to block very specific areas such as one foot one leg one arm or one side of the neck. In these cases a smaller group of nerves is blocked by injection of the local anesthetic into a specific area. Common painkillers for regional aesthesia include morphine and fentanyl which can be used in addition to a local anesthetic.
The final type of anesthesia is General anesthesia. This type of anesthesia is used for major surgery and temporarily makes you unconscious so that your brain does not perceive any pain signals from the nervous system. During that time no messages are processed and you cannot experience pain or other conscious sensations. General anesthesia can be administered as an inhaled gas or as an injected liquid. There are several drugs and gases that can be combined or used alone to produce general anesthesia. Most adults are first anesthetized with liquid intravenous anesthetics followed by anesthetic gases after they are asleep. Children however may not like having an injection or intravenous catheter placed in them while they are awake. Therefore they often breathe themselves to sleep with anesthetic gases given through a mask
It is very important that you follow whatever instructions you are given for not eating or drinking anything prior to any surgery. When you are given anesthesia you lose the ability to protect your lungs from inhaling. When you are awake you can usually swallow saliva and food without choking because part of the swallowing mechanism involves a reflex that results in covering the opening into the lungs. When you are anesthetized you lose that reflex. If you have any solids or liquids in your stomach during the time you are under anesthesia they could come up into your mouth and be inhaled into your lungs. The result could be very serious lung damage.