CHAPTER 3 who called it phlogisticated nitrous air. Priestley by other dentists. This probably was because in published his discovery in the book “Experiments January 1845, Wells had been partly unsuccessful NITROUS OXIDE – N2O (6 CE Hours) and Observations on Different Kinds of Air” at his first public demonstration of the use of (1775), where he described how to produce the nitrous oxide for the medical faculty in Boston, Learning objectives preparation of “nitrous air diminished” by heating leaving his colleagues doubtful regarding its ! Review the history of nitrous oxide. iron filings dampened with nitric acid. efficacy and safety. ! Describe the production of nitrous oxide. The method did not come into general use until ! List the uses of nitrous oxide. Early use (1794-1843) 1863, when Colton successfully started to use it ! Explain the use of nitrous oxide in dental The first important use of nitrous oxide was made in all his Colton Dental Association clinics, which operatories. possible by Thomas Beddoes and the renowned he just had established in New Haven and New ! Describe the hazards in the workplace. engineer James Watt, who worked together to York City. Over the following three years, Colton ! Review the methods of engineering control publish the book “Considerations on the Medical and his associates successfully administered and training. Use and on the Production of Factitious Airs” nitrous oxide to more than 25,000 patients. With (1794). This book was important for two reasons. its efficacy and safety now demonstrated by Introduction First, James Watt had invented a novel machine large numbers, the usage of nitrous oxide rapidly Sedation dentistry, sometimes called relaxation to produce “factitious airs” (i.e. nitrous oxide) became the preferred anesthetic method in dentistry, refers to the way dentists manage pain and a novel “breathing apparatus” to inhale dentistry. Because the gas is mild enough to keep and anxiety during dental appointments. the gas. Second, the book also presented the a patient in a conscious and conversational state new medical theories by Thomas Beddoes, that Conscious sedation is defined as a minimally but in most cases is strong enough to suppress tuberculosis and other lung diseases could be depressed level of consciousness that retains the pain caused by dental work, it remains the treated by inhalation of factitious airs. the patient’s ability to independently and preferred agent in dentistry today. continuously maintain an airway and respond The machine to produce factitious airs was In hospitals, however, nitrous oxide was appropriately to physical stimulation and verbal comprised of three parts: a furnace to burn the found not to be a strong enough for use command that is produced by pharmacological or needed material, a vessel with water where the in large operations. A stronger and more nonpharmacologic method or a combination of produced gas passed through in a spiral pipe (in potent anesthetic, sulfuric ether, was instead both. Nitrous oxide is only one of the 14 different order for impurities to be “washed off”), and demonstrated and accepted for use in October ways that sedation drugs can be administered. finally the gas cylinder with a gasometer where 1846, along with chloroform in 1847. When There are three primary ways that sedation is the produced air could be tapped into portable air Joseph Thomas Clover invented the “gas-ether administered in the dental office: IV sedation, bags (made of airtight oily silk). The breathing inhaler” in 1876, it became a common practice at enteral conscious sedation and inhalation apparatus was one of the portable air bags hospitals to initiate all anesthetic treatments with conscious sedation or nitrous oxide. connected with a tube to a mouthpiece. With this a mild flow of nitrous oxide, and then gradually new equipment engineered and produced already increase the anesthesia with the stronger ether/ in 1794, the way was now paved for clinical chloroform. Clover’s gas-ether inhaler was trials, which began when Thomas Beddoes in designed to supply the patient with nitrous 1798 established the Pneumatic Institution for oxide and ether at the same time, with the exact Relieving Diseases by Medical Airs in Clifton mixture controlled by the operator of the device. (Bristol). In the basement of the building, a large- It remained in use by many hospitals until the scale machine was producing the gases under 1930s. Although hospitals today are using a more the supervision of a young Humphry Davy, who advanced anesthetic machine, these machines still was encouraged to experiment with new gases 2 use the same principle launched with Clover’s N O for patients to inhale. The first important work of gas-ether inhaler, to initiate the anesthesia with Davy was to examine the nitrous oxide, with the Inhalation conscious sedation or the use of nitrous oxide before the administration of a more results being published in his book: “Researches, nitrous oxide, commonly known as laughing gas, powerful anesthetic. Chemical and Philosophical” (1800). is a chemical compound with the formula N2O. It is an oxide of nitrogen. At room temperature, it Despite the valuable finding made by Davy, Production is a colorless non-flammable gas with a pleasant, that inhalation of nitrous oxide could relieve a Nitrous oxide is most commonly prepared by slightly sweet odor and taste. It is used in surgery conscious person from pain, another 44 years careful heating of ammonium nitrate, which and dentistry for its anesthetic and analgesic would elapse before doctors attempted to use it decomposes into nitrous oxide and water vapor. effects. It is known as “laughing gas” because of for anesthesia. The addition of various phosphates favors the euphoric effects of inhaling it, a property that formation of a purer gas at slightly lower has led to its recreational use as a dissociative Anesthetic use temperatures. One of the earliest commercial hallucinogen. It is also used as an oxidizer in At a “popular science” exhibition in Hartford, producers was George Poe in Trenton, New Jersey. rocketry and in motor racing to increase the Connecticut, where volunteers inhaled nitrous ■ NH4NO3 (s) → 2 H2O (g) + N2O (g) power output of engine. At elevated temperatures, oxide, local dentist Horace Wells noted one of □ This reaction occurs between 170- nitrous oxide is a powerful oxidizer similar to them, a man who had injured his leg, seemed 240 degrees C, temperatures where molecular oxygen. For example, nitrous oxide in unaware of any pain from the injury. Thus ammonium nitrate is a moderately a test tube will re-ignite a smoldering splint. was the born the first use of nitrous oxide as sensitive explosive and a very powerful Nitrous oxide reacts with ozone and is the main anesthetic drug. Wells himself, with assistance by oxidizer. Above 240 degrees C, the naturally occurring regulator of stratospheric Gardner Quincy Colton and John Mankey Riggs, exothermic reaction may accelerate to ozone. It is also a major greenhouse gas and air demonstrated insensitivity to pain from a dental the point of detonation, so the mixture pollutant. Considered over a 100-year period, it extraction in December 1844. In the following must be cooled to avoid such a disaster. has 298 times more impact per unit weight than weeks, Wells treated the first 12-15 patients with Superheated steam is used to reach carbon dioxide. nitrous oxide in Hartford, and according to his reaction temperature in some turnkey own record, only failed in two cases. In spite of production plants. these convincing results reported by Wells to the History Downstream, the hot, corrosive mixture of gases medical society in Boston in December 1844, The gas was first synthesized by English chemist must be cooled to condense the steam and filtered this new method was not immediately adopted and Unitarian minister Joseph Priestley in 1772, to remove higher oxides of nitrogen. Ammonium Elite Page 13 nitrate smoke, as an extremely persistent colloid, In a 1914 patent, American rocket pioneer Robert only used by specialized planes like high-altitude will also have to be removed. The cleanup is often Goddard suggested nitrous oxide and gasoline as reconnaissance aircraft, high-speed bombers and done in a train of three gas washes, base, acid possible propellants for a liquid-fueled rocket. high-altitude interceptor aircraft. and base again. However, significant amounts of Nitrous oxide has been the oxidizer of choice One of the major problems of using nitrous oxide nitric oxide (NO) may not necessarily be absorbed in several hybrid rocket designs (using solid in a reciprocating engine is that it can produce directly by the base (sodium hydroxide) washes. fuel with a liquid or gaseous oxidizer). The enough power to damage or destroy the engine. The nitric oxide impurity is sometimes chelated combination of nitrous oxide with hydroxyl- Very large power increases are possible, and if the out with ferrous sulfate, reduced with iron metal terminated polybutadiene fuel has been used by mechanical structure of the engine is not properly or oxidized and absorbed in base as a higher SpaceShipOne and others. It is also notably used reinforced, the engine may be severely damaged oxide. The first base wash may (or may not) in amateur and high power rocketry with various or destroyed during this kind of operation. It is react out much of the ammonium nitrate smoke. plastics as the fuel. very important with nitrous oxide augmentation However, this reaction generates ammonia gas, Nitrous oxide can also be used in a of internal combustion engines to maintain proper which may have to be absorbed in the acid wash. monopropellant rocket. In the presence of a heated operating temperatures and fuel levels to prevent catalyst, N2O will decompose exothermically “pre-ignition” or “detonation” (sometimes referred Other routes into nitrogen and oxygen, at a temperature of to as “knocking” or “pinging”).