Anesthesia

Anesthesia

Also called: Anesthetic, Regional Anesthesia, Local Anesthesia

Summary

Anesthesia is defined as the loss of bodily sensation with or without loss of consciousness. It is used to numb mouth tissues or render a patient temporarily unconscious to block pain associated with dental procedures.  It works by blocking nerve endings, and may also reduce anxiety. Anesthesia is used for procedures such as fillings, root canals, tooth extractions and any other procedure that may produce discomfort.

There are two major forms of anesthesia:

  • Local anesthesia. Numbs the portion of the mouth where the dentist will be working. The dentist typically uses a needle to inject the anesthetic into the gum or inner cheek to block nerve endings and numb mouth tissues. Topical anesthetics are another form of local anesthetic. They typically are applied topically to numb an area before injecting the area with a local anesthetic. Local anesthesia is used for more frequently in dental procedures than general anesthesia.

  • General anesthesia. Puts patients to sleep so they are unconscious during the procedure. Under general anesthesia, patients do not feel any pain. When general anesthesia is used, it will be provided by someone with expertise in delivering the anesthesia and responding to any complications. Such experts include anesthesiologists, dental anesthesiologists and oral surgeons.

Local anesthesia typically is used for procedures such as fillings, root canals, crowns, extractions and treatment of gum disease. General anesthesia may be used for people (including children) who cannot calm down enough to be treated safely (dentophobic), or who have medical, physical or emotional disabilities that prevent them from following directions so they can be treated safely. It also may be used for patients undergoing unusually long or difficult procedures.

Patients who are going to use any form of anesthetic are urged to inform their dentist or other physician about any medications they are taking, including herbal supplements, because these can sometimes interact adversely with the anesthetic. Disclosing pre-existing medical conditions also is important prior to the procedure.

On the day of the procedure, patients are urged to follow the dentist’s preparatory instructions. Before administering the local anesthetic, a topical anesthetic that numbs the area may be applied.

If general anesthesia is to be used, the procedure may be performed either in a hospital or in an office equipped with proper monitoring equipment and trained staff. The anesthesia itself is inhaled or injected, and the patient quickly loses consciousness. During the procedure, the patient’s blood oxygen level, heart rate, blood pressure, temperature and breathing are monitored.

Areas that receive local anesthetic may feel numb for several hours after the procedure. This typically feels like a fat lip. Patients who receive general anesthetic may feel nauseous and may vomit after awakening.

Used correctly, anesthesia is very safe in all its forms. However, each form of anesthesia has its own risks and side effects. In particular, general anesthesia may cause serious complications in rare instances.

About anesthesia

Anesthesia is used to allow patients to feel comfortable during dental procedures such as fillings, root canals and oral surgery.

There are two major forms of anesthesia: local anesthesia and general anesthesia. Local anesthesia is used far more frequently in dental procedures than general anesthesia.

Local anesthesia numbs the portion of the mouth where the dentist will be working. The dentist typically uses a needle to inject the anesthetic into the gum or inner cheek to block nerve endings and numb mouth tissues.

Examples of local anesthetics include lidocaine, prilocaine, mepivacaine and bupivacaine. In addition to the anesthetic, the solution that is injected includes other substances, such as:

  • Vasoconstrictor. Narrows blood vessels, making the anesthetic’s effect last longer.
  • Antioxidant. Prevents the breakdown of the vasoconstrictor.
  • Sodium hydroxide. Adjusts the acidity of the solution to keep it working properly.
  • Sodium chloride. Helps the solution enter the bloodstream.

Local anesthesia may be injected as either a block injection (which numbs an entire region of the mouth) or infiltration injection (which numbs a smaller area). Researchers are also investigating a more precise form of local anesthesia that only affects a single tooth. The numbing effect of local anesthetics lasts for between one and several hours.

Topical anesthetics are another form of local anesthetic. These medicines are applied as ointments, gels, sprays or adhesive patches to skin or mucous membranes. Some topical anesthetics come in flavors, such as cherry and bubble gum. They numb the area to which they are applied. Dentists may use topical anesthetics to numb an area before inserting a needle into the area for a local anesthetic.

Topical anesthetics typically are made up of the same solutions used for local anesthetics. However, the dose of the topical may be stronger, because less of the anesthetic infiltrates the tissue when given topically. A topical may numb the nerves down to 2 to 3 millimeters (about 1/10 inch) below the surface for 15 to 30 minutes.

General anesthesia puts patients to sleep so they are unconscious during the procedure. Under general anesthesia, patients do not feel any pain. Medications used as part of general anesthesia include benzodiazepines, barbiturates, opioid analgesics and neuromuscular blocking agents.

When general anesthesia is used, it will be provided by someone with expertise in delivering the anesthesia, monitoring the patient and responding to any complications. Such experts include anesthesiologists, dental anesthesiologists and oral surgeons.

Patients who receive anesthetics during dental procedures should feel very little or no pain or discomfort. Patients who feel the anesthetic wearing off or who feel it is not working should notify their dentist immediately. In many cases, a dentist will arrange a signal with a patient before the procedure to serve as an alert in case of pain. For example, patients may be asked to raise a finger or hand if they experience discomfort.

Researchers are investigating new anesthetic processes for dental treatments. A new method called electronic anesthesia delivers electrical impulses through electrodes as a means of blocking pain. This technique allows patients to avoid needles completely. Another new technique involves injecting anesthetic directly into the jawbone. Known as an intraosseous injection, it can help to numb teeth directly. It takes less time to take effect and patients experience no pain with less numbness. Intraosseous injection can be used for any dental procedure, including fillings and root canals. There is also a new device that allows a very controlled, slow delivery of local anesthetic as the needle is advanced. This results in a pain free injection.

In addition to anesthesia, other forms of sedation may be used to help calm patients during dental procedures. These include conscious sedation, nitrous oxide and others.

Conditions treated with anesthesia

Local anesthesia typically is used for procedures such as fillings, root canals, crowns, extractions and treatment of gum disease. General anesthesia may be used for people who cannot calm down enough to be treated safely (e.g., children), or who have medical, physical or emotional disabilities that prevent them from following directions so they can be treated safely. It also may be used for patients undergoing unusually long or difficult procedures, such as surgical tooth extractions.

Dentists may use topical anesthetics to numb an area before inserting a needle into the area for a local anesthetic. Topicals also may be used for the following reasons:

  • Prevent the gag reflex due to insertion of impression trays or x-ray film
  • Reduce discomfort during scaling and root planing
  • Reduce discomfort during suture removal or during placement of a sedative dressing for a dry socket

Before procedures using anesthesia

If general anesthesia is going to be used, the patient may require a complete physical examination prior to the procedure. This ensures that the patient does not have a condition that could interfere with or be affected by the anesthesia.

Patients who are going to receive any form of anesthesia are urged to inform their dentist or other physician about any medications they are taking, including herbal supplements, because these can sometimes interact adversely with the anesthetic. Patients are also urged to be forthcoming about any illegal drugs they are taking, because certain drugs can cause potentially fatal reactions when taken with anesthesia.

Disclosing certain medical conditions also is important prior to the procedure. For example, some drugs used in general anesthesia can induce a condition called malignant hyperthermia. This is an inherited disease that causes muscular rigidity, high fever and metabolic changes. Patients with a family history of this disease should disclose the fact to their dentist or physician.

On the day of the procedure, patients are urged to follow their physician’s preparatory instructions. For example, patients receiving general anesthesia usually are asked to stop eating and drinking for a specified period of time (often overnight) prior to the procedure. This is done to clear the stomach. If the stomach is not clear, food can be aspirated into the lungs, resulting in serious complications.

Patients also are urged to bring any regular medications or other medical equipment (e.g., inhalers, glucose monitors) with them to the hospital if they will be staying overnight.

During procedures that use anesthesia

Before administering local anesthesia, the dentist may use a cotton swab or forced air to dry the area. Then, the area is swabbed or sprayed with a topical anesthetic that numbs the area after two to three minutes of continuous exposure. This prevents the patient from feeling the needle as it penetrates the mouth tissue. An anesthetic patch sometimes is used to deliver the topical instead of a spray or swab.

A local anesthetic is then injected into the patient’s cheek or gums. Despite the use of the topical anesthetic, patients may still feel a slight sting when the local anesthetic is injected. This is not caused by the needle, but rather by the effect of the medicine as it moves into the tissue.

If general anesthesia is to be used, the procedure is more likely to be performed in a hospital or same day surgery center. However, in some cases it can be performed in a dental office. Just prior to this procedure, an intravenous (I.V.) line is inserted into a vein. This delivers sedative drugs and any other medications that may be necessary.  A tube is placed in the patient’s windpipe (trachea) to help with breathing (intubation).

The anesthesia itself is inhaled or injected. In some cases, both techniques are used. The patient loses consciousness quickly. During the procedure, the patient’s blood oxygen level, heart rate, blood pressure, temperature and breathing are monitored.

After procedures that use anesthesia

Areas that receive a local anesthetic may feel numb for several hours after the procedure. This typically feels like a fat lip. Patients may find it difficult to speak clearly or to eat and drink. Patients also are urged to be careful not to bite the mouth or lip, because this can cause damage that will be painful once the anesthetic wears off.

Patients who receive general anesthesia may feel nauseated and may vomit after awakening. Patients should have someone else drive them home. Driving or operating heavy machinery is prohibited for 24 hours following the procedure. Patients often receive a prescription for medications that can help them manage any post-surgery pain.

Patients who have general anesthesia also are urged to avoid use of drugs that depress the central nervous system for at least 24 hours following the procedure. Such drugs include alcohol, tranquilizers, cold medications, allergy medications and muscle relaxants.

Potential risks with anesthesia

Local anesthesia is very safe, and there are few side effects associated with this medication. In rare cases, a swelling filled with blood (hematoma) may form if the needle hits a blood vessel. In other cases, the anesthetic may cause numbness in areas outside the region where the work is performed. For example, patients may experience drooping in the eyelids or corner of the mouth. This is due to the anesthetic spreading to and affecting the nerves that control these muscles. This can be disturbing to patients but the condition generally goes away when the local anesthetic wears off.

Though very rare, some patients may experience an allergic reaction to local anesthetics which is manifested as itching or rashes. The allergy is usually not to the local anesthetic itself but to the preservatives that are added to it. Patients should alert their dentist should this occur.

The vasoconstrictor in anesthetic solution may cause the heart to beat faster for a minute or two. The needle used to inject the solution can also injure a nerve, causing extended numbness and pain that usually heals over time.

Topical anesthetics also have very few risks. Some patients may have a mild allergic reaction that may cause swelling and raised welts on the skin that itch or burn. Severe allergic reactions are rare. It may be a day or two before the allergic reaction occurs.

Using excessive amounts of topical and local anesthetic can be toxic. Symptoms of toxicity include:

  • Blurred vision
  • Breathing difficulties
  • Dizziness or lightheadedness
  • Drowsiness
  • Headache
  • Ringing in the ears
  • Seizures
  • Shivering

Excessive amounts of topical anesthetic can also cause methemoglobinemia. This rare condition occurs when hemoglobin (a substance in red blood cells) is converted to an inactive form that fails to carry oxygen. In mild cases, the patient experiences no symptoms. More severe cases may be marked by fatigue, bluish or graying skin color, and breathing difficulties. The condition is treated with methylene blue which converts the inactive hemoglobin back to a normal functioning form.

Patients who have general anesthesia may feel nauseated afterward and may vomit. Other side effects include dizziness, drowsiness, headache, muscle aches, shivering, sore throat, vision problems and weakness. Most of these side effects disappear within 24 hours, although they can last for a few days.

Though very low, there is still risk of more serious complications associated with general anesthesia. In rare cases, patients have experienced stroke, heart attack, brain damage or even death. The risk of such complications partly depends on age, gender, weight, present medical condition, and history of use of tobacco, alcohol or drugs. In the vast majority of cases, complications that arise are safely managed by the experts who administer the anesthetic.

Questions for your doctor regarding anesthesia

Preparing questions in advance can help patients to have more meaningful discussions regarding their conditions. Patients may wish to ask their doctor the following questions related to anesthesia:

  1. Do any of my medical conditions or use of drugs prohibit me from using anesthesia?
  2. What form of anesthesia is most appropriate for me?
  3. Will sedatives or nitrous oxide be used in addition to the anesthetic?
  4. What are the potential risks or side effects that I face?
  5. If I need general anesthesia, will the procedure be performed in a dentist’s office or a hospital?
  6. Why do you think general anesthesia is a better option for me than local anesthesia?
  7. How should I prepare for having anesthesia?
  8. Should I make any temporary lifestyle changes following my use of anesthesia?
  9. What signs should I look for that might indicate a possible adverse reaction?
  10. Are there new methods of administering anesthesia that are available to me?
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