The administration of nitrous oxide is the most commonly used conscious sedation technique by dentists. It is used in over 30% of dental offices in US to provide anxiety free and painless dental treatments. Nitrous oxide sedation dentistry is an effective method of light dental sedation, and it is considered completely safe when it is administered by trained personnel and according to N2O usage guidelines.
Because of the ease of use, excellent safety record, and the many advantages vs other sedation methods, the use of nitrous oxide for dental sedation continues to increase in the US and the rest of the world. However each country (and many states in US) have different regulations on who and how can use nitrous oxide for sedation purposes.
Nitrous oxide is a colorless gas with a slight sweet odor and taste, which has analgesic and anxiolytic properties. It is an inhalation sedative; sedation is achieved by inhaling a mixture of nitrous oxide and oxygen through a mask placed over the nose. It reduces anxiety, pain, and memory of the treatment experienced.
The main steps in the process of nitrous oxide administration are the following:
Although N2O can be used for most of the patients, some nitrous oxide contraindications do exist for patients with certain conditions. The dentist must make sure that the patient is a suitable candidate for nitrous oxide sedation.
Medical history - An updated full medical and dental history of the patient must always be taken before any kind of sedation. If there is any concern or doubt, the patient’s physician must be consulted. The dentist will also ask if the patient had any problems or side effects in the past related to N2O usage.
Informed consent – In some countries the patient (or parent in case of children) must sign an informed consent form before receiving treatment (it is essential in countries like U.S. where malpractice lawsuits are common).
Patient instructions – The dentist must explain to the patient all the details of the procedure (and possible N2O side effects) and discuss what the patient must do if he has a problem during the course of treatment. Written instructions must be given to the patient concerning proper behavior before, during and after the procedure.
Final health assessment – Immediately before the administration of the nitrous oxide the dentist will do a final health assessment of the patient, asking for any recent health issues or symptoms, and measuring the patient’s vital signs (blood pressure and heart rate). Normal breathing rate is also recorded so that the correct volume of mixture is applied for the sedation.
Airway evaluation – The patient must be able to breath freely from the nose without problems. Free nasal airways are very important for proper inhalation sedation. If the nose is temporarily blocked, either the treatment must be postponed or another form of sedation should be used.
Patient relaxation – The patient is placed on the dental chair and the dentist creates a comfortable environment before administering the sedation. Relaxing music or television may be used to relax and also distract patients from their anxiety. A pillow or a blanket may also be provided to increase comfort.
The sedation gas is actually a mixture of nitrous oxide and oxygen, which is provided either from a central unit piped into the operating room or by a mobile unit. A flowmeter is used to adjust and monitor the relative concentration of each gas in the mixture.
A small rubber face mask is placed over the patient’s nose, through which the nitrous oxide and oxygen mixture is delivered. The patient is advised to breath normally through the nose and the sedation mask. The gas is administered through a valve in the mask, which releases gas only when the patient inhales through the nose. Since the sedative is received through inhalation, patients with needle-phobia can be more relaxed.
At the first phase of nitrous oxide sedation the patient breaths 100% oxygen for a few minutes until he gets used in breathing through the mask and feels comfortable with it.
As soon as the patient gets accustomed to breathing by the mask, the dentist will start to introduce the sedative gas. The percentage of nitrous oxide in the mixture is gradually increased (titration), while the dentist checks the patient’s response in order to understand when adequate sedation is achieved. Usually a mixture of at least 30% N2O (70% oxygen) is required for experiencing the analgesic and anxiolytic effects of nitrous oxide. Most patients will need a mixture of 50% N2O / 50% O2 to feel comfortable.
The dentist will provide the minimum amount of nitrous oxide required to achieve the desired sedation level for each individual patient’s needs. The patient begins to feel a pleasant level of sedation anywhere from 30 seconds to three or four minutes. After an initial feeling of light-headedness, a patient may experience a sense of well-being, euphoria, or floating. The administration of nitrous oxide must be controlled by an appropriately trained and licensed dental professional.
The analgesic effect of nitrous oxide can be adequate for certain treatments, eliminating the need for additional local anesthesia. Its numbing effect is stronger in the gingival tissues making nitrous oxide especially effective for treatments of gum disease. For some invasive procedures, after the patient is already sedated, the dentist will still have to provide local anesthesia to ensure that the patient will not experience any pain. However due to the numbing effect of the nitrous oxide on the gums, the injections of the anesthetic can be done without discomfort. After that, the dentist can proceed to the dental treatments.
At any time during the procedure, the dentist can strengthen or weaken the mixture depending on the patient’s comfort and level of relaxation. If a patient begins to feel uncomfortable, he should tell the dentist immediately and within seconds the dentist can adjust the the mixture to instantly change the level of sedation, and the patient will feel more comfortable again (either increasing N2O if the patient starts to feel pain or anxiety, or reducing it if the patient feels nausea).
The patient must be monitored continuously when under nitrous oxide sedation. The concentration of oxygen should never be less than 30% to prevent ‘hypoxia’. While the dentist is focused in performing the dental treatment, another staff member should monitor the measurements of the flowmeter which controls the N2O/O2 mixture, and the patient’s respiration by watching the inflation and deflation of the reservoir bag. A pulse oximeter to measure the concentration of oxygen in the blood is required when the administered N2O is over 50%. The dentist must maintain verbal contact with the patient, which must be able to respond without any problem. If there are signs that the patient feels sleepy or nauseous, the dentist must stop the administration of nitrous oxide.
The effects of nitrous oxide sedation are usually short lived, so full recovery is possible only some minutes after the sedative gas is discontinued. When the sedation dentistry treatment is completed, the patient will be given 100% oxygen (for about 3 to 5 minutes). After that time, almost 99% of the nitrous oxide has cleared the body, and the patient feels back to normal. Otherwise oxygen is provided for a few more minutes until full recovery. In most cases the dentist will allow nitrous oxide sedated patients to leave the office without escort and drive home by themselves, as soon as they feel fully alert and awake.