Characteristics and Properties of Nitrous Oxide

The characteristics and properties of nitrous oxide are as follows:

• It reduces or eliminates anxiety.

• It cannot produce profound surgical anesthesia. It can be used as a substitute to local anesthesia in minor procedures (small restorations and a supplement to local anesthesia) but not in extensive procedures (extractions).

• It reduces the gag reflex but not the cough reflex.

• There is minimal or nonexistent toxicity when used on healthy patients for a reasonable length of time.

• It is highly insoluble in blood and water (resulting in quick absorption and elimination by the patient).

• Ninety-nine percent of its elimination from the body is through the lungs without significant biotransformation (has minimal effect on other organ systems).

• It is not metabolized through the liver (little interaction with other drugs except for enhancing the effects of sedative and anti-anxiety drugs).

• It is heavier than air with a specific gravity of 1.53. This property is helpful when introducing nitrous oxide/oxygen to an extremely anxious patient by placing the nasal hood a few inches above an anxious patient with the nitrous oxide to descending into the patient’s nose, enabling gradual desensitization to the experience.

• Is gas at room temperature, but when compressed into a cylinder becomes a liquid.

• Is non-flammable, however, it can support combustion. (If placed near an open flame, will burn brighter.)

• At extreme altitudes (above 10,000 feet), there is a need for an increase in concentration (~5%) to obtain the same effect.

• Nitrous oxide is a colorless and virtually odorless gas with a faint, sweet smell. It causes central nervous system (CNS) depression and euphoria with little effect on the respiratory system.

• The analgesic effect appears to be initiated by neuronal release of endogenous opioid peptides with subsequent activation of opioid receptors and descending Gamma-aminobutyric acid type A (GABAA) receptors and noradrenergic pathways that modulate nociceptive processing at the spinal level. The anxiolytic effect involves activation of the GABAA receptor either directly or indirectly through the benzodiazepine binding site.

• Nitrous oxide has rapid uptake, being absorbed quickly from the alveoli and in a simple solution in the serum.

• It is relatively insoluble, passing down a gradient into other tissues and cells in the body, such as the CNS.

• As nitrous oxide is 34 times more soluble than nitrogen in blood, diffusion hypoxia may occur and administering 100% oxygen to the patient for minimum of 5 minutes once the nitrous oxide has been terminated is important.

• Nitrous oxide causes minor depression in cardiac output while peripheral resistance is slightly decreased, thereby maintaining blood pressure.

The objectives of nitrous oxide/oxygen inhalation include:

• Reduce or eliminate anxiety.

• Reduce untoward movement and reaction to dental treatment.

• Enhance communication and patient cooperation.

• Raise the patient’s pain reaction threshold.

• Increase tolerance for longer appointments.

• Aid in the treatment of the mentally/physically disabled or medically compromised patient.

• Reduce gagging.

• Potentiate the effects of sedatives.³