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 bio-transformation (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 3-5 minutes once the nitrous oxide has been terminated is important.
  • Nitrous oxide causes minor depression in cardiac output while peripheral resisatnce 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