Nitrous oxide for anxiolysis (minimal sedation) in dentistry

Nitrous oxide (combined with oxygen and administered via a nasal mask) is an established, safe and effective technique for anxiolysis (minimal sedation) in dentistry. The use of nitrous oxide for anxiolysis was previously known as relative analgesia. Nitrous oxide can be used for apprehensive patients, and to facilitate treatment in patients who could not otherwise be managed in a general dental practice. Nitrous oxide is the preferred agent to facilitate dental treatment in anxious or uncooperative children. Nitrous oxide also reduces the gag reflex. Advantages and disadvantages of oral benzodiazepines and inhaled nitrous oxide for anxiolysis in dentistry lists the advantages and disadvantages of nitrous oxide. Adverse effects are described below.

Carefully consider the appropriateness of nitrous oxide for anxiolysis—see Patient groups at increased risk of adverse outcomes with anxiolysis (minimal sedation) for a list of patients at increased risk of adverse outcomes. Nitrous oxide is contraindicated in patients with a condition where air is trapped within a body cavity (eg pneumothorax, bowel obstruction, recent middle ear surgery) because nitrous oxide may increase the pressure or volume within such spaces.

Effective delivery of nitrous oxide depends on good flow through the nasal passages, so confirm there is no nasal congestion or obstruction before administration.

Nitrous oxide is administered starting at a low concentration, and then titrated to clinical effect. It is commonly administered at a concentration of 50% for anxiolysis for dental procedures. In most purpose-built equipment, there is an inbuilt safety feature that does not allow more than 70% nitrous oxide to be delivered to the patient.

Nitrous oxide has a rapid onset of action. Response varies between individuals; at a concentration of 50% nitrous oxide, peak effect would be expected in a 70 kg adult within 3 to 5 minutes. Monitor the patient clinically at all times, preferably with pulse oximetry. Resuscitation equipment must be available. Use nitrous oxide in a well-ventilated area with an appropriate scavenging device to minimise room air contamination and staff exposure. Repeated nitrous oxide exposure may be associated with spontaneous first-term miscarriage in staff; inform staff of this risk.

When nitrous oxide administration is stopped, recovery is rapid because the drug is rapidly removed from the body. If nitrous oxide has been administered for 10 minutes or longer, it is common practice to administer supplemental oxygen for 3 to 5 minutes after nitrous oxide is stopped, to prevent an abrupt decrease in oxygen saturation of arterial blood. Monitor the patient’s clinical response and recovery.

The main adverse effects of nitrous oxide relate to the development of hypoxia. Even with the commonly used concentration of 50%, nitrous oxide is capable of occasionally producing loss of consciousness, and impaired cough and gag reflexes. Some children have a paradoxical reaction to nitrous oxide. Other adverse effects are rare and include nausea, vomiting, hypotension and respiratory effects.