The characteristics and properties of nitrous oxide are as follows:
- It reduces or eliminates anxiety.
- It cannot produce profound surgical anaesthesia. It can be used as a substitute to local anaesthesia in minor procedures (small restorations and a supplement to local anaesthesia) 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 colourless and virtually odourless 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 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
