Differences Between Anesthesia and Sedation
The information presented on this site is of personal opinion and consequently is slanted and biased and not based on proper scientific research. The information presented is NOT written by a dental expert. Further the information presented has NOT been subjected to peer review by experts to verify accuracy and data integrity.
The common term used to describe differences between anesthesia provided is sedation dentistry. There are different anesthesia options available to you depending on your choices and your comfort level. Sedation is used to reduce anxiety and seperate painkillers will have to also be given. One should verify with their surgeon that he or she is properly trained and licensed in what sedation option they prefer and also discuss the different options with them.
There are many different terms used to describe anesthesia. There are different kinds of sedation and different levels of sedation that can be provided. In the order of increasing anesthesia these are local anesthesia, minimal sedation, nitrous oxide/oxygen, moderate (conscious) sedation, deep sedation, and general anesthesia. [18, 19, 23] It is possible to also not be given anesthesia.
An estimate of the cost of these different sedation types is provided on a seperate page.
Local anaesthesia eliminates the sensation of pain by blocking nerve signals to the brain in a certain part of the body by being injected into the area, sprayed directly on to the area, or rubbed on to the area. It is most often an injection into the gum surrounding the tooth. 
The treated area will very quickly start to lose feeling and the area will go numb. The operation won't start until the doctor is absolutely sure that the area is numb. It is important to realise that local anaesthesia takes away feelings of pain, but it is possible to still feel pressure, vibration, movement, or sounds. Patients who only have local anesthesia will be fully awake. 
No special preparations to treatment will have to be made while under a local anaesthetic. Thus eating and drinking as normal before surgery will occur. If there are any concerns talk to the surgeon or doctor.
The most common local anesthetic used by oral and maxillofacial surgeons is lidocaine (Xylocaine). Lidocaine can be used with or without epinephrine. Other local anesthetics used include bupivacaine (Marcaine), mepivacaine (Carbocaine), articaine (Septocaine), and prilocaine (Citanest). A local anesthetic used in a small percentage of cases from 1988 until being withdrawn from the U.S. market in 2002 was etidocaine (Duranest). The first synthetic local anesthetic was porcaine (Novocaine), which is an ester unlike all the local anesthetics named above which are amides. Novocaine is no longer used today in dentistry. Today amide local anesthetics are often combined with a vasporessor/vasoconstrictor either epinephrine (adrenaline) or levonordefrin with the purpose being to constrict blood vessels to prevent bleeding and prolong the effective duration. [10, 11, 12, 13, 14, 16, 17, 20]
The following are amide local anesthetic formulations used: [15, 16, 17, 20]
- 2% lidocaine (Xylocaine) with 1:100,000 epinephrine (most often used - considered gold standard)
- 4% articaine (Septocaine) with 1:200,000 epinephrine
- 4% articaine (Septocaine) with 1:100,000 epinephrine
- 4% prilocaine (Citanest Forte) with 1:200,000 epinephrine
- 0.5% bupivacaine (Marcaine) with 1:200,000 epinephrine
- 2% mepivacaine (Carbocaine) with 1:20,000 levonordefrin (Nordefrin, Neo-Cobefrin)
- 3% mepivacaine (Carbocaine) without epinephrine
- 4% prilocaine (Citanest Plain) without epinephrine
- 2% lidocaine (Xylocaine) without epinephrine
- 2% lidocaine with 1:50,000 epinephrine
Also available and used more in Canada is 2% mepivacine with 1:100,000 epinephrine. The onset of action for the amide local anesthetics range from the shortest being 2 to 3 minutes for articaine while bupivacaine takes the longest at 6 to 10 minutes for onset to occur. The amide local anesthetics available provide the doctor with a range of durations of action. Lidocaine, articaine, prilocaine, and mepivacaine with a vasoconstrictor provide an expected pupal duration for around 60 minutes. The longest with a vasoconstrictor is 0.5% bupivacaine which an expected pupal duration of 90 to 180 minutes (nerve block). Without a vasoconstrictor (referred to as plain) the shortest expected pupal duration is 5 to 10 minutes for 2% lidocaine and the longest expected pupal duration is 40 to 60 minutes for 4% prilocaine (nerve block). [16, 17, 20, 21]
The following ester anesthetics can also be used: 
- propoxycaine and procaine (Ravocaine)
- topical benzocaine
This image is from http://www.flickr.com/photos/travis5447/2918229917/. It is used with permission.
Having only local anesthesia has the least amount of potential complications that can occur but certainly permanent nerve damage and even death can occur.
Minimal sedation is a drug-induced state during where one responds normally to verbal commands. Although cognitive function and physical coordination may be impaired, airway reflexes, and ventilatory and cardiovascular functions are unaffected. 
Oral surgeons and dentists typically use nitrous oxide / oxygen as minimal sedation, although it may also be considered moderate sedation. [14, 18]
Nitrous Oxide (Laughing Gas) / Oxygen Sedation
Nitrous oxide is commonly known as laughing gas and one is awake and aware of what is going on around them. Nitrous oxide is administered with a mask via inhalation along with an oxygen mixture. Inhalation allows for the gas to be introduced into the lungs and for absorption through the gas/blood interface to occur. If there is little anxiety this approach may be given. 
A local anesthetic while having nitrous oxide will also be given to help with pain. Nitrous oxide/oxygen can be used in combination with other sedative agents. 
Unfortunately there have been instances where the gas lines controlling the nitrous oxide and oxygen are mixed up which has led to brain damage, loss of neurological function, and even death.
Discussion on Greater Levels of Sedation that Follow Below
Moderate (conscious) sedation, deep sedation, and general sedation is commonly injected using a fine plastic tube (called a cannula) into a vein on the back of one's hand or in their arm. This causes a sharp sensation, like an injection, that passes quickly.
With the cannula in place, the oral surgeon or anesthesiologist can give the various drugs and control pain and nausea, without repeated injections. One may also be put on a drip so they can be kept hydrated. Many oral surgeons receive hospital-based anesthesia training and are licensed to administer office-based moderate sedation.  An anesthesiologist will take on this role when greater levels of sedation are given such as with general anesthesia.
Typically, one must not eat or drink for about six to eight hours before sedation and anesthesia is given. If one is given certain medications when they have recently eaten they could vomit and throw up which could become life threatening. In addition, an empty stomach will prevent one from feeling sick.
Prior to surgery the oral surgeon or anesthesiologist will ask about one's medical health and history and about any previous experience they have had of office based or hospital treatment. It's important to inform the oral surgeon or anesthesiologist about any allergies and whether one suffers from asthma, hayfever or eczema. In addition, any medications one is taking will need to be told.
Smoking should be given up before being given sedation and anesthesia for at least a few days. Any make-up, nail varnish, jewelery, contact lenses, glasses, dentures, and/or hearing aids will need to be removed. In addition the oral surgeon and/or anaesthetist should be made aware of any dental crowns, bridges or loose teeth.
Which sedative drug or drugs are given will depend on the doctor's training and possible school of thought.
Sedatives can sometimes affect one's breathing. Continued monitor of breathing (respiration rate), heart rate, heart rhythm, blood pressure, and oxygenation during the surgery will occur. The heart rate and heart rhythm will be monitored via electrocardiogram (ECG/EKG). The amount of oxygen in one's blood will be monitored constantly by pulse oximetry through a small clasp on their finger and they may also be given extra oxygen through a mask or a plastic tube. When deep sedation or general anesthesia is given temperature will also be monitored. Monitoring of breath sounds via ausculation and/or end end-tidal CO2 may also occur. [7, 19]
To help control pain during and after surgery, one may be given painkillers. These can be injected through the cannula, or given as a suppository. Muscle relaxants may also be given so the surgeon can operate more easily.
When the anaesthetic gases are stopped, one will begin to wake up or recover quite quickly. They will be given a drug to reverse the effects of any muscle relaxant.
They will then be moved to a recovery room where a nurse will provide one-to-one care. The nurse will continue to monitor heart rate, blood pressure, and other vital body functions.
When one starts to wake up, they may feel sleepy or disorientated for 15 minutes or so. They may experience a sore throat and/or feel sick.
Once the nurse or anaesthetist is happy with one's progress, they will be disconnected from monitors. When they no longer need intravenous medicines or fluids that may have been given, the cannula and drip will be removed.
With moderate (conscious) sedation one can typically go home after a 20 to 30 minute recovery. With greater levels of sedation and general anesthesia this period of time before they can be sent home may be a few hours. 
The effects of any sedative and anesthestic may last longer than one would expect and temporarily affect co-ordination and reasoning skills. For this reason, one must not drive, drink alcohol, perform any strenous activity, operate machinery or sign legal documents until at least 24 hours with sedation and at least 48 hours with general anesthesia after the surgery. One should arrange for somebody to stay with them at home for the first 24 hours and have someone to drive them home after the surgery.
An advantage of moderate (conscious) sedation, deep sedation, and general anesthesia is the ability to titrate to effect. This means that a small incremental dose of a drug is intially given and one is monitored. Addition small incremental doses are given until a desired effect such as sleepiness is reached. Knowledge of each drug's time of onset, peak response and duration of action by the surgeon or anesthesiologist administering it allows for oversedation to not occur. When moderate (conscious) sedation is given the surgeon or anesthesiologist must wait until they know whether the previous dose has taken full effect before administering an additional drug increment. [7, 19]
Moderate (Conscious) Sedation
Moderate (conscious) sedation is a drug-induced depression of consciousness during which one responds purposefully to verbal commands, either alone or accompanied by light tactile stimulation. No interventions are required to maintain a patent airway, and spontaneous ventilation is adequate (meaning you can breathe normally). Cardiovascular function is usually maintained.  Moderate (conscious) sedation can be acheived with parenteral agents (ie. intravenous (IV), intramuscular, intraosseous, intranasal, submucosal, subcutaneous medications). [14, 18]
With moderate (conscious) sedation one may be given an oral medication (as in pill to swallow) prior to arriving at the dental office or hospital prior to surgery.
With moderate (conscious) sedation, in the dental setting, one will most commonly have intravenous (IV) sedation and/or oral sedation. One may have difficulty remembering (amnesia) everything that occured and is not as aware as with just nitrous oxide.
Sedative drugs don't block the pain signals to the brain, so local anaesthesia is often given with intravenous (IV) sedation. In addition pain killers may also be given.
If you elect to have intravenous (IV) sedation you may want to discuss with your doctor what drug or drugs he/she would like to administer as the leading experts in dental sedation agree that the fewer medications used, the safer the treatment. Some of these drugs can cause also lead to sexual hallucinations which could lead to difficulty in distinguishing from sexual assault. Thus a chaperone or nurse should be present when one is given intravenous (IV) sedation so that a hallucination can be clearly distinguished from sexual assault which in rare cases has unfortunately occured.
The overwhelming majority of people who have their wisdom teeth removed elect to have moderate (conscious) sedation.  Moderate sedation can lead to numerous complications and even death such as if an overdose is accidentally given, the pharmacology of the drug(s) is not understood, and drug-drug interactions occur.
Deep sedation is a drug-induced depression of consciousness during which one cannot be easily aroused but responds purposefully following repeated or painful stimulation. The ability to independently maintain ventilatory function may be impaired. One may require assistance in maintaining a patent airway, and spontaneous ventilation may be inadequate. Cardiovascular function is usually maintained. 
Oral surgeons and dentists typically group deep sedation together with general anesthesia. Deep sedation can also be achieved with IV sedation. However, deep sedation is not really thought of as being used in the dental profession. 
General anesthesia is a drug-induced loss of consciousness during which one is not arousable, even by painful stimulation. The ability to independently maintain ventilatory function is often impaired. One will often require assistance in maintaining a patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function (meaning breathing often is controlled by a breathing tube and ventilator). Cardiovascular function may be impaired. 
General anaesthesia allows for a doctor to put one to sleep and keep them asleep for surgery. They will be unconscious. It is generally administered in a hospital by an anesthesiologist. When one has a general anaesthetic they will not feel or remember the operation as they will be in a deep sleep. General anaesthesia may be used in cases where one is very apprehensive about surgery or has a disability.
Drugs and Medications Given During Sedation and General Anesthesia
There are many different types of medications and drugs that can be given for sedation (minimal, moderate (conscious), deep) and general anesthesia and in conjunction.
In conscious sedation an opioid narcotic, a benzodiazapine, barbiturate, or other parenteral agents can be used or a combination of these. Narcotics used include fentanyl (sublimaze), meperidine (demerol), morphine, and hydromorphone (dilaudid). Benzodiazapines used include diazepam (valium), midazolam (versed), triazolam (halcion), and lorazepam (ativan). Barbiturates include secobarbital (seconal) and pentobarbital (nembutal) Other parenteral agents used include ketamine, methohexital (brevital), propofol (diprivan), flumazenil (romazicon), and naloxone (narcan). [10, 16]
With general anesthesia vapors that are used can include sevoflurane, isoflurane, halothane, and desflurane. These could be used with conscious sedation, although not as common.
Other medications that can be used along with general anesthesia or conscious sedation include codeine (methyl morphine), methadone (Dolophine), oxycodone (Perocet), atropine, dexamethasone, glycopyrrolate, nalbuphine (nubain), thiopental (pentothal), scopolomine, droperidol, penthrane, enflurane, phenergan, chloral hydrate, innovar, talwin. Some of the medications listed have fallen out of use and replaced by other drugs, particularly the latter ones in this paragraph. They are primarily provided here for historical information and may still be used in developing countries. [10, 11, 12, 13, 14, 16]
Local Anesthesia versus Sedation versus General Anesthesia
Local anaesthesia and sedation are commonly performed and generally safe procedures. In many cases there are clear advantages over general anaesthesia, such as speed of recovery and lower risk of complications. However, in order to make an informed decision and give properly give consent, one should be aware of the possible side-effects and the risk of complications.
Sedation can cause headaches, drowsiness for longer than expected durations, make one feel nauseous, cause one to be sick and vomit, and cause feelings similar to those of a hangover. Most people have some difficulty remembering aspects of the procedure (amnesia) and in rare cases unpleasant memories of the procedure. With any procedure involving anaesthesia there is a very small risk of an unexpected allergic reaction to the anaesthetic. With intravenous (IV) sedation and general anesthesia irritation of the vein where the injection occured (phlebitis) can occur.
General anaesthesia side-effects are mostly temporary. After having a general anaesthetic, one may have a sore throat, a headache, or feel tired and confused for a couple of days. Uncommon complications include chest infections and difficulty breathing, damage to teeth, lips or tongue. Serious complications as a result of anaesthesia do occur, but they are extremely rare such as damage to the eyes, serious allergic reactions to medications, and nerve damage. It's estimated that serious complications result in 1 death in every 162,000 cases to 1 in every 1.733 million cases in dental offices. See the mortality rates in dentistry page to read how this figure was determined.
Awareness under general anesthesia occurs when surgical patients can recall their surroundings and sometimes even pain, related to their surgery. Clinical studies have demonstrated that anesthesia awareness occurs in roughly one patient per thousand receiving general anesthesia.
The exact risks will differ for every person.
Brain Monitoring Devices
Brain monitoring devices (also called brain function monitors, consciousness monitors or depth of anesthesia monitors) provide anesthesia professionals a method to assess patient responses during surgery, in addition to observation of clinical signs and conventional monitoring of vital signs. Brain monitoring technologies are employed by a growing number of anesthesia professionals to help assess patient consciousness and adjust the amount of anesthetic medication during surgery in order to avoid over and under dosing. They measure brain wave activity.
Recent studies have demonstrated that using a brain monitoring device such as a BIS monitor during an operation is an effective method to decrease the chance of awareness. A BIS monitor reduces the frequency of awareness more than 5-fold. BIS monitoring helps anesthesia professionals recognize those periods of an operation when more anesthesia medication is needed to stay asleep, or identify potential problems with the anesthesia medications.
A number of studies involving thousands of patients have shown the additional benefits when an anesthesia professional uses a BIS monitor to help adjust the amount of medications that are received during an operation. Typically, the amount of medication given is reduced by one-fifth. As a result, patients generally wake up faster at the end of surgery, have less nausea and vomiting, and are able to leave the recovery room sooner.
To watch a video to understand how anesthesia works on the body and how a brain monitor can help an anesthesia professional give patients the right amount of anesthesia go to the following link http://www.businesswire.com/cgi-bin/mmg.cgi?eid=5547695
If the above link does not work for the video go here http://www.teethremoval.com/anesthesia_brain.wmv
Final Note on Anesthesia
The surgeon should have the training, skills, drugs, and equipment to identify and manage any emergency situation that may occur until paramedics can arrive or until the person experiencing the emergency event has no airway or cardiovascular complications. Unfortunately there has been a case that occured where a dentist locked himself in the office during an emergency.  Hence dentists, surgeons, and doctors can panic in the event of an emergency that may occur even if they have all the training, skills, drugs, and equipment at their disposal which puts their patient at risk for a potentially serious complication or even death. Unfortunately, there have also been cases where surgeons do not have all the needed training, skills, drugs, and equipment which has lead to death. Due to these risks, it may be safer to have surgery performed in a hospital (or at minimum close proximity) where other doctors and medical professionals can quickly assist the surgeon if a medical emergency occurs. Certainly having an experienced, well educated, and trained surgeon is also important.
Updated December 16, 2011
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