Nitrous oxide and oxygen sedation

Inhaled sedation with a mixture of nitrous oxide and oxygen (N₂O/O₂) is a method of minimal “conscious” sedation in which the patient breathes a controlled gas mixture through a nasal mask. The patient stays conscious, breathes independently and keeps protective airway reflexes and the ability to respond to instructions.

The method reduces anxiety, provides mild pain relief and makes treatment easier to tolerate. It takes effect in 30–60 seconds, with the maximum effect after about 5 minutes. Nitrous oxide is not metabolized and leaves the body unchanged through the lungs, so recovery after the gas is stopped is quick. Sedation is given when indicated, after an examination by the doctor.

How the procedure goes

• The patient sits comfortably in the chair, and the doctor fits a nasal mask of the right size.
• For the first 1–2 minutes, the patient breathes pure oxygen.
• The doctor then gradually raises the nitrous oxide concentration in small steps to the right level of relaxation. For minimal sedation it does not exceed 50 percent; 20–40 percent is usually enough for dentistry.
• In most cases, local anesthesia is also used: the pain-relieving effect of nitrous oxide is weak, and its job is to relieve anxiety.
• The doctor keeps talking with the patient throughout. The patient holds their mouth open unaided, a clinical sign that the level of sedation is adequate; mouth props are not used.
• At the end, the patient breathes pure oxygen for a few minutes to prevent diffusion hypoxia.

How the patient's condition is monitored

With minimal sedation, monitoring is based on clinical observation and continuous verbal contact. The staff who perform sedation are trained in basic and advanced cardiopulmonary resuscitation. Heart rate, blood oxygen saturation and blood pressure are also tracked: before the start, about every 10 minutes during the procedure and at the end.

With adequate sedation, the patient is awake and relaxed, spontaneous movement is reduced, pulse, blood pressure and breathing rate are normal, and the laryngeal reflex is preserved. If the patient becomes markedly detached, dizzy or nauseous, or finds it hard to keep their mouth open, the doctor lowers the gas concentration.

If nitrous oxide is combined with other sedatives or the concentration exceeds 50 percent, sedation becomes deeper, and monitoring standards for that level apply, including capnography.

Side effects

• The most common is nausea and vomiting: 2–14 percent according to pediatric data. The risk is higher when opioids are added and at higher gas concentrations.
• Dizziness, voice changes, euphoria, laughter, tingling in the limbs, a feeling of detachment.
• Diffusion hypoxia if the gas is stopped abruptly, prevented by breathing oxygen at the end of the procedure.
• Headache; rarely, raised blood pressure and heart rhythm disturbances.
• With long or repeated exposure, blood and neurological effects linked to vitamin B₁₂ inactivation.

Safety profile

The method has a good safety profile when used by trained staff at concentrations appropriate for conscious sedation.

• In an analysis by the Pediatric Sedation Research Consortium (1,634 administrations), adverse events occurred in 6.5 percent, vomiting in 2.4 percent and serious adverse events in 0.2 percent, with no cases of aspiration.
• In a pediatric emergency department program over 10 years (831 sedations), no serious adverse events were recorded.
• No deaths or serious morbidity have been reported with nitrous oxide used as the only agent at appropriate concentrations.
• In adults undergoing endoscopy, nitrous oxide gave faster recovery and fewer drops in blood pressure and desaturation than intravenous sedation.