Nitrous oxide or laughing gas was discovered in 1772 by British chemist <PERSON>, who also discovered oxygen. His compatriot, <PERSON>, later named the gas and experimented on himself to discover its physiological effects. It is prepared by the action of zinc on dilute nitric acid, by the action of hydroxylamine hydrochloride on sodium nitrite, or more commonly, by gently heating ammonium nitrate to decompose it into nitrous oxide and water vapor.
For the first 40 years or so, N2O was primarily used for parties or public shows. In the 1840s, American dentist <PERSON> had one of his own teeth extracted while inhaling nitrous oxide, thereby demonstrating its anesthetic effect. It was then widely used for dental anesthesia until it was abandoned for a time because the high concentrations required to anesthetize sufficiently frequently placed the patient at high risk of severe hypoxia and death from asphyxia.
Use of N2O was resumed at subanesthetic concentrations for analgesic and anxiolytic applications without unconsciousness, such as pain relief during labor, self-administration by cancer patients, clinical and emergency applications, dental work and widely used with children to alleviate their fear of medical or dental treatment.
This nonflammable, colorless gas with a pleasant, sweetish odor and taste has been used for nearly 150 years without much understanding of how it really works. It is well recognized as an anxiolytic, an analgesic and an anesthetic but its mechanisms of action are not clear. Recent studies are beginning to shed some light on the question.
The air we breathe in is composed of 21% O2, 0.4% CO2, 78%N2 and less than 1% of other gasses, mainly Argon. The air we breathe out is composed of 16,4% O2 and 4,4% CO2, due to our intake of oxygen and release of carbon dioxide. It has been biotransformed by the passage through our lungs. 978
When we breathe in N2O, we breathe out N2O in the same concentration. There is no biotransformation, and no new oxygen has entered our bloodstream. This deprives the blood of O2.
When our brain has been deprived of O2 to a certain point, we feel nauseous and light headed, our thinking capacity decreases and we experience mental confusion. At the same time, NO2 causes the release of dopamine in the brain, inducing a sense of euphoria, accompanied with relaxation, giggling, laughter, insensitivity to pain, possible tingling in the extremities, sometimes nausea and dizziness. If this goes on too long without ventilation, it can lead to hypoxia and paralysis. In fact, medical and dental practitioners are particularly vulnerable to a long term overdose of N2O because the nitrous they administer to their patients is returned to the room’s air unchanged and accumulates to unhealthy concentrations without proper ventilation. Long time use may lead to vitamin B12 deficiency with all of its symptoms, not surprisingly since vitamin B12 is essential to the formation of red blood cells which are affected with oxygen deprivation.
The anesthetic effect power of N2O was determined to be equivalent to 10 to 15mg of morphine, when administered at 30% concentration. Further studies determined that its effect is opioid in nature and like morphine, may involve a myriad of neuromodulators in the spinal cord. Research is continuing to better understand the mechanisms of action of N2O, but it is safe to say that it should not be used as a recreational drug. 978