Nitrous oxide is commonly used in surgical and dental procedures as an anesthetic and pain reducer. The World Health Organization includes nitrous oxide on its list of essential medicines. It is sometimes known as laughing gas, as it creates a euphoric effect upon inhalation; for this reason, it is also abused as a recreational drug. Because of its stability and relative safety, nitrous oxide is also used as a rocket propellant and in internal combustion engines used in auto racing, and it is commonly used as an aerosol propellant for whipped cream and cooking sprays.
Nitrous oxide has been used for medical and dental purposes since the mid-1800s. In clinical use, nitrous oxide is currently administered in a 2:1 ratio with oxygen and administered through a medical ventilator. If the dosage ratio is incorrect and the levels of nitrous oxide are too high, this can cause side effects including headaches, shivering or sweating, nausea or vomiting, and fatigue; however, these side effects are rare, as dosage is closely monitored and carefully administered. Nitrous oxide is a relatively weak anesthetic and is rarely used alone as such, instead used as a carrier gas with more powerful anesthetic drugs when intended for general anesthesia. Dentists use nitrous oxide without these accompanying anesthetic drugs to relax patients who will remain conscious throughout dental procedures, which allows the patients to respond to questions and follow dentist’s instructions. Nitrous oxide is also commonly used to relieve pain during childbirth and in instances of trauma.
Although nitrous oxide is comparably non-toxic, when related to other gases, it can adversely affect human health and shares some of the same dangers as any compressed liquefied gas. In poorly ventilated rooms, prolonged patient exhalation of nitrous oxide can pose a hazard to other people in the room; for this reason, dental clinics usually have advanced ventilation systems. Nitrous oxide exposure leads to decreased mental acuity, manual dexterity, audiovisual aptitude, and disorientation. When used recreationally, without oxygen added, nitrous oxide may also cause oxygen deprivation, which may lead to lowered blood pressure, fainting, or coronary attack. Long-term exposure to nitrous oxide may lead to deficiency of vitamin B12, and people with existing B12 deficiencies should avoid exposure.
In the United States, it is a federal offense to possess nitrous oxide; because it is used in culinary applications, many states regulate the amounts that can be sold or possessed by individuals and restrict its possession by minors. Recreational use of nitrous oxide has been common since the early 1800s, when British elites regularly had what were known as “laughing gas parties.” As nitrous oxide became more available for culinary use, its recreational use also expanded. Nitrous oxide, a greenhouse gas, contributes to global climate change and ozone-layer depletion; its recreational use has also caused environmental problems, as spent nitrous oxide cartridges are a common source of litter in areas where it is widely used recreationally. The nitrous oxide that damages the ozone layer and the atmosphere is primarily a byproduct of nitrogen-based fertilizers like animal manure, which accounts for about 80% of nitrous oxide released in the U.S. The nitrous oxide used as a dental anesthetic has a negligible effect on the atmosphere.