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”). Most problems The direct oxidation of ammonia may someday approximately 1,300 degrees C. Because of the that are associated with nitrous do not come from rival the ammonium nitrate pyrolysis synthesis large heat release, the catalytic action rapidly mechanical failure due to the power increases. of nitrous oxide mentioned above. This capital- becomes secondary as thermal autodecomposition Since nitrous allows a much denser charge into intensive process, which originates in Japan, uses becomes dominant. In a vacuum thruster, this the cylinder, it dramatically increases cylinder a manganese dioxide-bismuth oxide catalyst: can provide a monopropellant specific impulse pressures. The increased pressure and temperature

■■ 2 NH3 + 2 O2 → N2O + 3 H2O (Isp) of as much as 180s. While noticeably less can cause problems, such as melting the piston □□ Higher oxides of nitrogen are formed as than the Isp available from hydrazine thrusters or valves. It may also crack or warp the piston or impurities. In comparison, uncatalyzed (monopropellant or bipropellant with nitrogen head and cause pre-ignition due to uneven heating. ammonia oxidation (i.e. combustion or tetroxide), the decreased toxicity makes nitrous

explosion) goes primarily to N2 and H2O. oxide an option worth investigating. Aerosol propellant The gas is approved for use as a food additive (also Nitrous oxide can be made by heating a solution Specific impulse (I ) can be improved by sp known as E942), specifically as an aerosol spray of sulfamic acid and nitric acid. Many gases are blending a hydrocarbon fuel with the nitrous propellant. Its most common uses in this context are made this way in Bulgaria. oxide inside the same storage tank, becoming a in aerosol whipped cream canisters, cooking sprays ■■ HNO + NH SO H → N O + H SO + H O nitrous oxide fuel blend (NOFB) monopropellant. 3 2 3 2 2 4 2 and as an inert gas used to displace oxygen and □□ There is no explosive hazard in this This storage mixture does not incur the danger of inhibit bacterial growth when filling packages of reaction if the mixing rate is controlled. spontaneous ignition because N O is chemically 2 potato chips and other similar snack foods. However, as usual, toxic higher oxides of stable. When the nitrous oxide decomposes by nitrogen are formed. a heated catalyst, high-temperature oxygen is The gas is extremely soluble in fatty compounds. In aerosol whipped cream, it is dissolved in Nitrous oxide is produced in large volumes as released and rapidly ignites the hydrocarbon fuel the fatty cream until it leaves the can, when it a byproduct in the synthesis of adipic acid, one blend. NOFB monopropellants are capable of I greater than 300 seconds, while avoiding the becomes gaseous and thus creates foam. Used in of the two reactants used in nylon manufacture. sp this way, it produces whipped cream four times This might become a major commercial source, toxicity associated with hypergolic propulsion the volume of the liquid, whereas whipping air but will require the removal of higher oxides systems. The low freezing point of NOFB eases into cream only produces twice the volume. If of nitrogen and organic impurities. Currently, thermal management compared to hydrazine and air were used as a propellant, oxygen would much of the gas is decomposed before release dinitrogen tetroxide – a valuable property for accelerate rancidification of the butterfat; nitrous for environmental protection. Greener processes space storable propellants. oxide inhibits such degradation. Carbon dioxide may prevail that substitute hydrogen peroxide Internal combustion engine cannot be used for whipped cream because it is for nitric acid oxidation; hence no generation of In vehicle racing, nitrous oxide (often referred to acidic in water, which would curdle the cream oxide of nitrogen by-products. as just “nitrous” or as NOS after the name of the and give it a seltzer-like “sparkling” sensation. Hydroxylammonium chloride can react with brand Nitrous Oxide Systems) allows the engine to However, the whipped cream produced with sodium nitrite to produce N O as well: burn more fuel and air, resulting in a more powerful 2 nitrous oxide is unstable and will return to a ■■ NH OH+Cl− + NaNO → N O + NaCl + 2 H O combustion. The gas itself is not flammable, but 3 2 2 2 liquid state within half an hour to one hour. Thus, □□ If the nitrite is added to the it delivers more oxygen than atmospheric air by the method is not suitable for decorating food that hydroxylamine solution, the only breaking down at elevated temperatures. will not be immediately served. remaining byproduct is salt water. Nitrous oxide is stored as a compressed liquid; the However, if the hydroxylamine solution Similarly, cooking spray, which is made from evaporation and expansion of liquid nitrous oxide is added to the nitrite solution (nitrite is various types of oils combined with lecithin (an in the intake manifold causes a large drop in intake in excess), then toxic higher oxides of emulsifier), may use nitrous oxide as a propellant; charge temperature, resulting in a denser charge, nitrogen are also formed. other propellants used in cooking spray include further allowing more air/fuel mixture to enter the food-grade alcohol and propane. Applications cylinder. Nitrous oxide is sometimes injected into (or prior to) the intake manifold, whereas other Users of nitrous oxide for recreational use as a Rocket motors systems directly inject right before the cylinder euphoria-inducing inhalant drug, often obtain it Nitrous oxide can be used as an oxidizer in a (direct port injection) to increase power. from whipped cream dispensers that use nitrous oxide as a propellant. It is not harmful in small rocket motor. This has the advantages over other The technique was used during World War II by doses, but risks due to lack of oxygen do exist oxidizers that it is non-toxic, and because of its Luftwaffe aircraft with the GM-1 system to boost (see Recreational section). stability at room temperature, easy to store and the power output of aircraft engines. Originally relatively safe to carry on a flight. As a secondary meant to provide the Luftwaffe standard aircraft Recreational use benefit, it can be readily decomposed to form with superior high-altitude performance, breathing air. Its high density and low storage Nitrous oxide (N2O) is a dissociative drug that technological considerations limited its use to can cause analgesia, depersonalization, dizziness, pressure enable it to be highly competitive with extremely high altitudes. Accordingly, it was stored high-pressure gas systems. euphoria and some sound distortion. Research Page 14 Elite has also found that it increases suggestibility However, an investigation in 2009 by the including nitrous oxide. They noted there are and imagination. Inhalation of nitrous oxide for Bristol (Va.) Herald Courier reported that the three elements that put a practitioner at risk: recreational use to cause euphoria and slight records of 46 health care professionals in the treating a patient without an assistant in the hallucinations began as a phenomenon for the area – including doctors, nurses, pharmacists and operatory, high concentrations of nitrous oxide, British upper class in 1799 at “laughing gas dentists – were “marred by substance abuse, and and failure to titrate the patient to avoid extension parties.” When equipment became more widely in some cases, criminal convictions.” of therapeutic sedation. available for dentistry and hospitals, most The Herald Courier told the story of a Big Stone “Nitrous oxide should be employed with countries also restricted the legal access to buy Gap, Va., dentist who “huffed nitrous oxide in the confidence. Employing simple guidelines will pure nitrous oxide gas cylinders to those sectors. mid-1970s and quit only after a temporary loss ensure there are no difficulties with sexual issues A low availability of equipment to produce the of feeling in his hands.” From there, the dentist and the administrator of nitrous oxide,” they said. gas combined with a low usage of the gas for descended into alcoholism and took Valium and medical purposes meant recreational use was Hydrocodone from his office, the newspaper said. In medicine a relatively rare phenomenon that mainly took Nitrous oxide has been used for anesthesia in A grassroots drug-recovery group of Virginia place among students at medical universities. dentistry since December 1844, when Horace th dentists directed the man to a rehab program. The That apparently continued into the 20 century. A Wells made the first dental operations with state board of dentistry got an anonymous call poll taken in 1979 indicated that between 1 and the gas in Hartford. Its debut as a generally about his situation. Instead of disciplinary action, 2 percent of medical and dental students used accepted method came in 1863, when Gardner the board helped monitor his recovery. According nitrous oxide for recreational purposes, according Quincy Colton introduced it more broadly at all to the newspaper, keeping addictions confidential to Theodore J. Jastak in a 1991 article in the the Colton Dental Association clinics. The first is at the discretion of either a Department of Health Journal of the American Dental Association. devices used in dentistry to administer the gas, Professions investigator or a licensing board. In the 1960 and ’70s, the recreational use of known as nitrous oxide inhalers, were designed inhalants became somewhat fashionable again, A board of medicine official said the policy in a very simple way, with the gas stored and according to a Consumers Union report in protected the public by “making sure the breathed through a breathing bag made of rubber 1972 based on reports of use in Maryland and individual is identified and investigated, set cloth, without a scavenger system and flow meter, Vancouver and a survey at the University of for an evaluation and treatment, and continue and with no addition of oxygen/air. with monitoring. They (the Virginia monitoring Michigan in 1970. Today these simple and somewhat unreliable program) will not OK a doctor to go back into inhalers, of course, have been replaced by the According to the Michigan survey: “It was not practice until he or she is believed to be safe.” uncommon [in the interviews] to hear from more modern relative analgesia machine, which individuals who had been to parties where a That is a common practice. The Federation of is an automated machine designed to deliver professional (doctor, nurse, scientist, inhalation State Physician Health Programs Inc. (FSPHP) a precisely dosed and breath-actuated flow of therapist, researcher) had provided nitrous oxide. evolved in 1990 from an initiative of the American nitrous oxide mixed with oxygen for the patient There also were those who work in restaurants Medical Association and individual state physician to inhale safely. The machine used in dentistry health programs that focus upon rehabilitation who used the N2O stored in tanks for the is designed as a more simplified version of the preparation of whip cream. Reports were received and monitoring of physicians with psychoactive larger anesthetic machine used by hospitals, and it from individuals who used the gas contained in substance abuse disorders as well as mental doesn’t feature the additional anesthetic vaporizer aerosol cans both of food and non-food products. and physical illness. The nonprofit organization and medical ventilator. The machine allows for At a rock festival, nitrous oxide was widely sold includes members from 42 state programs. a more simple design, because it only delivers a for 25 cents a balloon. Contact was made with FSPHP serves as a resource for state programs; mixture of nitrous oxide and oxygen for the patient a ‘mystical-religious’ group that used the gas helps to establish monitoring standards; serves to inhale to depress the feeling of pain while to accelerate arriving at their transcendental- as an informational source; advocates for keeping the patient in a conscious state. meditative state of choice. Although a few more physicians and their health issues at local state The relative analgesia machine typically features sophisticated users employed nitrous oxide- and national levels; and helps states in their quest a constant-supply flow meter, which allows the oxygen mixes with elaborate equipment, most to protect the public. The organization promotes proportion of nitrous oxide and the combined gas users employed balloons or plastic bags. They confidentiality for health care professionals who flow rate to be individually adjusted. The gas is either held a breath of N O or rebreathed the gas. 2 chose to address their substance problems and administered by dentists through a demand-valve There were no adverse effects reported in the submit to rigorous monitoring of their progress. inhaler over the nose, which will only release more than 100 individuals surveyed.” A 2003 report in the Journal of the California gas when the patient inhales through the nose. Although recreational use is believed to be Dental Association [Malamed and Clark] cited Because nitrous oxide is minimally metabolized somewhat limited today, government data on concerns about abuse of nitrous oxide by health in humans (with a rate of 0.004 percent), it substance abuse of youths shows that inhalants, care professionals. The authors said nitrous retains its potency when exhaled into the room including nitrous oxide, are being used by oxide causes euphoria and can include “sexual by the patient and can pose an intoxicating and young people. phenomena,” including increased feelings of prolonged exposure hazard to the clinic staff if the room is poorly ventilated. Where nitrous The Substance Abuse and Mental Health Services sexuality and arousal, and therefore has the oxide is administered, a continuous-flow fresh-air Administration (SAMHSA) said in its 2007 potential for abuse. “This abuse is usually not ventilation system or nitrous scavenger system is report on trends in drug use that almost 1 million as addictive as some drugs, but nonetheless can used to prevent a waste-gas buildup. youth had used inhalants within the past year. The be a steppingstone to other drugs and can cause percentage of young people aged 12-17 who had incapacitation of the affected person. Nitrous oxide Hospitals are administering nitrous oxide as one used all inhalants within the past year was lower should be given the same respect as all drugs.” of the anesthetic drugs delivered by anesthetic in 2007 (3.9 percent) than in 2003 (4.5 percent), The typical abuser of nitrous oxide is older and machines. Nitrous oxide is a weak general in 2004 (4.6 percent), and in 2005 (4.5 percent). middle- or upper class, they said. If the abuser anesthetic, and so is generally not used alone Among first-time users, the rate of use of nitrous has an inhalation sedation unit available, it may in general anesthesia. In general anesthesia it is oxide, or “whippets” – usually canisters of the have been altered to deliver a higher concentrate used as a carrier gas in a 2:1 ratio with oxygen propellants to create whipped cream – declined of gas, they said. for more powerful general anesthetic, drugs between 2002 and 2007 among males (40.2 such as sevoflurane or desflurane. It has a MAC percent to 20.2 percent) and females (22.3 The authors noted there have been reports of (minimum alveolar concentration) of 105 percent percent to 21.2 percent). sexual abuse of patients under anesthetics, and a blood gas partition coefficient of 0.46.

Elite Page 15 When nitrous oxide is inhaled as the only anesthetic Euphoric effect As with many strong oxidizers, contamination of drug, it is normally administered as a mixture with In rats, N2O stimulates the mesolimbic reward parts with fuels have been implicated in rocketry 30 percent gas and 70 percent oxygen. pathway via inducing dopamine release and accidents, where small quantities of nitrous/fuel activating dopaminergic neurons in the ventral mixtures explode due to “water hammer-like” Neuropharmacology tegmental area and nucleus accumbens, effects (sometimes called “dieseling” – heating

The pharmacological mechanism of action of N2O presumably through antagonization of NMDA caused by adiabatic compression of gases that can in medicine is not fully known. However, it has receptors localized in the system. This action reach decomposition temperatures). Some common been shown to directly modulate a broad range of has been implicated in its euphoric effects, building materials, such as stainless steel and ligand-gated ion channels, and this likely plays and notably, appears to augment its analgesic aluminum, can act as fuels with strong oxidizers a major role in many of its effects. It moderately properties as well. such as nitrous oxide, as can contaminants, which blocks NMDA and β -subunit-containing nACh can ignite due to adiabatic compression. 2 However, it is remarkable that in mice, N O channels; weakly inhibits AMPA, kainate, GABA 2 C blocks amphetamine-induced and dopamine There have also been accidents where nitrous and 5-HT receptors; and slightly potentiates 3 release in the nucleus accumbens and behavioral oxide decomposition in plumbing has led to the GABA and glycine receptors. It has also been A sensitization, abolishes the conditioned place explosion of large tanks. shown to activate two-pore-domain K+ channels. preference (CPP) of cocaine and morphine, and While N O affects quite a few ion channels, 2 does not produce reinforcing (or aversive) effects Biological its anesthetic, hallucinogenic and euphoriant of its own. Studies on CPP of N O in rats is Nitrous oxide inactivates the effects are likely caused predominantly or fully 2 mixed, consisting of reinforcement, aversion and cobalamin form of vitamin via inhibition of NMDAR-mediated currents. In no change. In contrast, it is a positive reinforcer B by oxidation. Symptoms addition to its effects on ion channels, N O may 12 2 in squirrel monkeys, and is well known as a of vitamin B deficiency, act to imitate nitric oxide (NO) in the central 12 drug of abuse in humans. These discrepancies nervous system as well, and this may relate to its including sensory neuropathy in response to N O may reflect specie variations analgesic and anxiolytic properties. 2 and encephalopathy, can occur or methodological differences. It is noteworthy within days or weeks of exposure that in human clinical studies, N O was found Anxiolytic effect 2 to nitrous oxide anesthesia in to produce mixed responses similarly to rats, In behavioral tests of anxiety, a low dose of N O people with subclinical vitamin 2 reflecting high subjective individual variability. is an effective anxiolytic, and this anti-anxiety B12 deficiency. Symptoms are effect is associated with enhanced activity of treated with high doses of vitamin Neurotoxicity GABA receptors as it is partially reversed by B , but recovery can be slow and A Similarly to other NMDA antagonists like 12 benzodiazepine receptor antagonists. Mirroring incomplete. People with normal ketamine, N O has been demonstrated to this, animals that have developed tolerance to the 2 vitamin B levels have stores produce neurotoxicity in the form of Olney’s 12 anxiolytic effects of benzodiazepines are partially to make the effects of nitrous lesions (damage to the posterior cingulate and tolerant to N O. Indeed, in humans given 30 oxide insignificant, unless exposure is repeated 2 retrosplenial cortices) in rodents upon prolonged percent N O, benzodiazepine receptor antagonists and prolonged (nitrous oxide abuse). Vitamin 2 (e.g., several hours) exposure. However, it also reduced the subjective reports of feeling “high,” B levels should be checked in people with risk simultaneously exerts widespread neuroprotective 12 but did not alter psychomotor performance in factors for vitamin B deficiency prior to using effects via inhibiting glutamate-induced and it 12 human clinical studies. has been argued that on account of its very short nitrous oxide anesthesia.

Analgesic and anti-nociceptive effect duration under normal circumstances, N2O may A study of workers and several experimental

The analgesic effects of N2O are linked to the not share the neurotoxicity of other NMDA animal studies indicate that adverse reproductive interaction between the endogenous opioid system antagonists. Indeed, in rodents, short-term effects for pregnant females may also result from and the descending noradrenergic system. When exposure results in only mild injury that is rapidly chronic exposure to nitrous oxide. animals are given morphine chronically, they reversible, and permanent neuronal death only Flammability develop tolerance to its pain-killing effects, and this occurs after constant and sustained exposure. Nitrous oxide is a non-flammable gas at room also renders the animals tolerant to the analgesic temperature. effects of N2O. Administration of antibodies that Safety bind and block the activity of some endogenous The major safety hazards of nitrous oxide come The National Fire Protection Association has not opioids (not β-endorphin) also block the anti- from the fact that it is a compressed liquefied gas, assigned a flammability rating to nitrous oxide: nociceptive effects of N2O. Drugs that inhibit the an asphyxiation risk and a dissociative anesthetic. ■■ Flash point: Not applicable. breakdown of endogenous opioids also potentiate Exposure to nitrous oxide causes short-term ■■ Autoignition temperature: Not applicable. the anti-nociceptive effects of N2O. Several decreases in mental performance, audiovisual ■■ Flammable limits in air: Not applicable. experiments have shown that opioid receptor ability and manual dexterity. Long-term exposure ■■ Extinguishant: For small fires, use dry antagonists applied directly to the brain block the can cause vitamin B12 deficiency, numbness, chemical or carbon dioxide. Use water spray, anti-nociceptive effects of N2O, but these drugs reproductive side effects and other problems. fog or standard foam to fight large fires have no effect when injected into the spinal cord. The National Institute for Occupational Safety involving nitrous oxide.

Conversely, α2-adrenoceptor antagonists block and Health recommends that workers’ exposure Fires involving nitrous oxide should be fought the anti-nociceptive effects of N2O when to nitrous oxide should be controlled during upwind from the maximum distance possible. given directly to the spinal cord, but not when the administration of anesthetic gas in medical, Keep unnecessary people away; isolate the applied directly to the brain. Indeed, α2B- dental and veterinary operators. hazard area and deny entry. Isolate the area for adrenoceptor knockout mice or animals depleted ½-mile in all directions if a tank, rail car or tank in norepinephrine are nearly completely resistant Chemical/physical truck is involved in the fire. For a massive fire At room temperature (20 degrees C), the saturated to the anti-nociceptive effects of N2O. It seems in a cargo area, use unmanned hose holders or vapor pressure is 58.5 bar, rising up to 72.45 N2O-induced release of endogenous opioids monitor nozzles; if this is impossible, withdraw causes disinhibition of brain stem noradrenergic bar at 36.4 degrees C – the critical temperature. from the area and let the fire burn. Emergency neurons, which release norepinephrine into the The pressure curve is thus unusually sensitive to personnel should stay out of low areas and spinal cord and inhibit pain signaling. Exactly temperature. Liquid nitrous oxide acts as a good ventilate closed spaces before entering. Vapors solvent for many organic compounds; liquid how N2O causes the release of endogenous opioid are an explosion hazard indoors, outdoors or in peptides is still uncertain. mixtures may form shock-sensitive explosives. sewers. Containers of nitrous oxide may explode

Page 16 Elite in the heat of the fire and should be moved from gas cylinder rules (1985) permit the transfer of of conception was not significantly different the fire area if it is possible to do so safely. If gas from one cylinder to another for breathing from that of the unexposed assistants. Because this is not possible, cool fire-exposed containers purposes. This law benefits remote hospitals, environmental exposures were not measured from the sides with water until well after the fire which would otherwise suffer because of during these epidemiologic studies, no dose- is out. Stay away from the ends of containers. India’s geographic immensity. Nitrous oxide effect relationship could be established. Firefighters should wear a full set of protective IP is transferred from bulk cylinders (17,000 Exposure to high concentrations of waste clothing and self-contained breathing apparatus liters capacity gas) to smaller pin-indexed anesthetic gases – even for a short time – may when fighting fires involving nitrous oxide. valve cylinders (1,800 liters of gas), which cause the following health effects: are then connected to the yoke assembly of ■■ Headache. Environmental Boyle’s machines. Because India’s Food and ■■ Irritability. Nitrous oxide is a greenhouse gas, accounting for Drug Authority (FDA-India) rules state that ■■ Fatigue. about 6 percent of the heating effect of greenhouse transferring a drug from one container to another ■■ Nausea. gases in the atmosphere. According to 2006 data (refilling) is equivalent to manufacturing, ■■ Drowsiness. from the United States Environmental Protection anyone found doing so must possess a drug- ■■ Difficulties with judgment and coordination. Agency, industrial sources make up only about 20 manufacturing license. ■■ Liver and kidney disease. percent of all anthropogenic sources, and include the production of nylon and the burning of fossil Nitrous oxide in dental operatories Workers exposed fuel in internal combustion engines. Human activity The Engineering Control Technology Branch In 1983, the American Dental Association (ADA) is thought to account for 30 percent; tropical (ECTB) of the Division of Physical Sciences and reported that 35 percent of all dentists used N2O soils and oceanic release account for 70 percent. Engineering studies the aspects of health hazard to control pain and anxiety in their patients [ADA However, a 2008 study by Nobel Laureate Paul prevention and control in the workplace. Nitrous 1983]. The ADA 1991 Survey of Dental Practice Crutzen suggests that the amount of nitrous oxide oxide (N O) mixed with oxygen has been used 2 indicated that 58 percent of dentists reported release attributable to agricultural nitrate fertilizers in dentistry as an analgesic and as a sedative for having N2O anesthetic equipment, and 64 percent has been seriously underestimated, most of which more than 100 years. Today, more than 424,000 of those practitioners also reported having a would presumably come under soil and oceanic workers who practice dentistry (such as dentists, scavenging system. The percentage of pediatric release in the Environmental Protection Agency dental assistants and dental hygienists) in the dentists using N O increased from 65 percent in data. Nitrous oxide also causes ozone depletion. A United States are potentially exposed to N O. 2 2 1980 to 88 percent in 1988. recent study suggests that N2O emission currently is In a technical report published in 1977, the the single most important ozone-depleting substance National Institute for Occupational Safety and Occupational exposure limits (ODS) emission and is expected to remain the Health recommended controlling exposure limits The Occupational Safety and Health largest throughout the 21st century. of nitrous oxide waste to 25 parts per million Administration (OSHA) does not currently have a parts (ppm) of air during dental surgery. The standard for N O. Legality 2 report presented methods for limiting the waste The NIOSH recommended exposure In the United States, possession of nitrous oxide during administration, based on the technical is legal under federal law and is not subject to limit (REL) for N2O is 25 ppm as a time- feasibility of existing controls. Since publication weighted average (TWA) during the period DEA purview. It is, however, regulated by the of this technical report, data collected by Food and Drug Administration under the Food of anesthetic administration [NIOSH 1977b]. NIOSH have shown occupational exposures as This REL is intended to prevent decreases in Drug and Cosmetics Act; prosecution is possible high as 300 ppm in hospital operating rooms under its “misbranding” clauses, prohibiting mental performance, audiovisual ability and and exposures higher than 1,000 ppm in dental manual dexterity during exposures to N O. A the sale or distribution of nitrous oxide for the operatories equipped with scavenging systems 2 purpose of human consumption. recommended exposure limit to prevent adverse (properly operating scavenging systems have reproductive effects cannot be established until been shown to reduce N O concentrations by Many states have laws regulating the possession, 2 more data are available. sale and distribution of nitrous oxide. Such laws more than 70 percent). The scavenging systems usually ban distribution to minors or limit the use local exhaust ventilation to collect waste The American Conference of Governmental amount of nitrous oxide that may be sold without gases from anesthetic breathing systems and Industrial Hygienists’ (ACGIH) threshold limit special license. remove them from the workplace. value (TLV) for N2O is 50 ppm as an eight-hour time-weighted average [ACGIH 1993]. The 1991 In the state of California, possession for recreational Effects of exposure to high concentrations Documentation of the Threshold Limit Values use is prohibited and qualifies as a misdemeanor. Animal studies have shown adverse reproductive and Biological Exposure Indices states that In some countries, it is illegal to have nitrous effects in female rats exposed to airborne “control to this level should prevent embryo-fetal toxicity in humans and significant decrements oxide systems plumbed into an engine’s intake concentrations of N2O. Data from these studies in human psychomotor and cognitive functions manifold. These laws are ostensibly used to indicate that exposure to N2O during gestation can prevent street racing and to meet emission produce adverse health effects in the offspring. or other adverse health effects in exposed standards. Nitrous oxide is entirely legal to personnel” [ACGIH 1991]. Several studies of workers have shown that possess and inhale in the United Kingdom, occupational exposure to N O causes adverse although supplying it to others to inhale, 2 Medical surveillance effects such as reduced fertility, spontaneous especially minors, is more likely to end up with a OSHA is currently developing requirements for abortions and neurologic, renal and liver disease. prosecution under the Medicines Act. medical surveillance. When these requirements A recent study reported that female dental are promulgated, readers should refer to them for In New Zealand, the Ministry of Health has warned assistants exposed to unscavenged N O for five 2 additional information and to determine whether that nitrous oxide is a prescription medicine, and or more hours per week had a significant risk employers whose employees are exposed to its sale or possession without a prescription is an of reduced fertility compared with unexposed nitrous oxide are required to implement medical offense under the Medicines Act. This statement female dental assistants. The exposed assistants surveillance procedures. would seemingly prohibit all non-medicinal uses had a 59 percent decrease in probability of of the chemical, though it is implied that only conception for any given menstrual cycle Medical screening recreational use will be legally targeted. compared with the unexposed assistants. For Workers who may be exposed to chemical In India, for general anesthesia purposes, nitrous dental assistants who used scavenging systems hazards should be monitored in a systematic during N O administration, the probability oxide is available as nitrous oxide IP. India’s 2 program of medical surveillance that is intended Elite Page 17 to prevent occupational injury and disease. The Termination medical evaluations □□ Informs workers about proper work program should include education of employers The medical, environmental and occupational practices, controls, equipment and and workers about work-related hazards, early history interviews; the physical examination; and protective gear that should be used when detection of adverse health effects and referral selected physiologic or laboratory tests that were working with N2O. of workers for diagnosis and treatment. The conducted at the time of placement should be ■■ Use the guidelines in the following section to occurrence of disease or other work-related repeated at the time of job transfer or termination minimize worker exposures to N2O. adverse health effects should prompt immediate to determine the worker’s medical status at the evaluation of primary preventive measures (e.g., end of his or her employment. Any changes in the Guidelines for minimizing industrial hygiene monitoring, engineering worker’s health status should be compared with worker exposures controls, and personal protective equipment). those expected for a suitable reference population. A medical surveillance program is intended Exposure monitoring to supplement, not replace, such measures. To Biological monitoring Exposure monitoring should be the first step in detect and control work-related health effects, Biological monitoring involves sampling and developing work practices and worker education medical evaluations should be performed (1) analyzing body tissues or fluids to provide programs, because measurements of N2O are before job placement, (2) periodically during the an index of exposure to a toxic substance or needed to determine the type and extent of term of employment, and (3) at the time of job metabolite. No biological monitoring test controls that are necessary. Follow the guidelines transfer or termination. acceptable for routine use has yet been developed below to minimize worker exposures: for nitrous oxide. ■■ Monitor for N2O when the anesthetic equipment Preplacement medical evaluation is installed and every three months thereafter. Before a worker is placed in a job with a Workplace monitoring and measurement Include the following types of monitoring: potential for exposure to nitrous oxide, a licensed Determination of a worker’s exposure to airborne □□ Leak testing of equipment. health care professional should evaluate and nitrous oxide can be made using one of the □□ Monitoring of air in the worker’s document the worker’s baseline health status following techniques: personal breathing zone. with thorough medical, environmental and ■■ A Landauer Passive Dosimeter badge, which □□ Environmental (room air) monitoring. occupational histories, a physical examination, can be used for a minimum sampling duration ■■ Prepare a written monitoring and and physiologic and laboratory tests appropriate of one hour (maximum duration 40 hours). maintenance plan for each facility that uses for the anticipated occupational risks. These Analysis is performed by the manufacturer N2O . This plan should be developed by should concentrate on the function and integrity of the badge as described in the OSHA knowledgeable persons who consider the of the respiratory, reproductive, central Computerized Information System. equipment manufacturers’ recommendations, nervous and hematological systems. Medical ■■ An ambient air or bag sample with a frequency of use and other circumstances that surveillance for respiratory disease should be minimum collection volume of two might affect the equipment. conducted using the principles and methods spectrophotometer cell volumes. Analysis is ■■ Perform air monitoring by gasbag sampling recommended by the American Thoracic conducted using a long-path-length portable or real-time sampling. Society. A preplacement medical evaluation is infrared spectrophotometer as described in ■■ When real-time sampling is conducted to recommended to assess medical conditions that NIOSH Method No. 6600. obtain personal exposure data, attach the may be aggravated or may result in increased sampling train to the lapel of the worker risk when a worker is exposed to nitrous oxide Personal hygiene procedures on the side closest to the patient; N2O at or below the prescribed exposure limit. The If liquid nitrous oxide contacts the skin, workers concentrations in this location are most health care professional should consider the should flush the affected areas immediately with representative of those in the worker’s probable frequency, intensity and duration of tepid water to reduce the likelihood of frostbite. breathing zone. Diffusive samplers (referred to as passive dosimeters) are commercially exposure as well as the nature and degree of any A large population of health care workers is available and may be useful as initial applicable medical condition. Such conditions potentially exposed to N O, and NIOSH has 2 indicators of exposures. (which should not be regarded as absolute documented cases in which exposures substantially contraindications to job placement) include exceed existing recommended exposure limits. Engineering controls and maintenance a history and other findings consistent with NIOSH has concluded that exposure to N O 2 procedures diseases of the respiratory, reproductive, central causes decreases in mental performance, The following engineering controls and nervous or hematological systems. audiovisual ability and manual dexterity. Data maintenance procedures have been shown to be from animal studies demonstrate that exposure Periodic medical evaluations feasible and effective in reducing exposure to to N O may cause adverse reproductive effects. Occupational health interviews and physical 2 N O during anesthetic administration. Studies of workers exposed to N O have reported 2 examinations should be performed at regular 2 adverse health effects such as reduced fertility, Anesthetic delivery. Excessive exposure to N2O intervals during the employment period, as spontaneous abortion, and neurological, renal, may occur as a result of leaks from the anesthetic mandated by any applicable federal, state or local and liver disease. The recommendations in a 1994 delivery system during administration. The standard. Where no standard exists and the hazard NIOSH alert should therefore be followed to rubber and plastic components of the anesthetic is minimal, evaluations should be conducted minimize worker exposures. equipment are potential sources of N O leakage every three to five years or as frequently as 2 because they may be degraded by the N2O and recommended by an experienced occupational Recommendations the oxygen as well as by repeated sterilization. health physician. Additional examinations may Engineering controls, work practices and respirators Take the following steps to control N O exposure be necessary if a worker develops symptoms (when necessary) should be used to minimize the 2 from anesthetic delivery systems: attributable to nitrous oxide exposure. The exposure of workers to N O. Employers should 2 ■■ Use connection ports with different- interviews, examinations and medical screening ensure that their workers are adequately protected diameter hoses for N O and O2 to reduce the tests should focus on identifying the adverse from N O exposure by taking the following steps: 2 2 possibility of incorrectly connecting the gas effects of nitrous oxide on the respiratory, ■■ Monitor airborne concentrations of N O. 2 delivery and scavenging hoses. reproductive, central nervous or hematological ■■ Implement appropriate engineering controls, ■■ Check all rubber hoses, connections, tubing systems. Current health status should be work practices and maintenance procedures. and breathing bags daily and replace them compared with the baseline health status of the ■■ Institute a worker education program that: when damaged or when recommended by individual worker or with expected values for a □□ Describes standard operating procedures for suitable reference population. the manufacturer. all tasks that may expose workers to N2O. Page 18 Elite ■■ Following visual inspection, perform leak □□ Permanently connected to the scavenging that the proper amounts of N2O and air are testing of the equipment and connections by system vacuum line. being delivered to the patient.  using a soap solution to check for bubbles □□ Positioned so that it is always visible to  Flush the system of N2O after surgery by at high-pressure connections. For a more the operator. administering oxygen to the patient through the thorough inspection of all connectors, use a ■■ Maintain the flow meter by cleaning anesthetic equipment for at least five minutes portable infrared spectrophotometer (such as a and recalibrating it according to the before disconnecting the gas delivery system.  Miran 1A or 1B) calibrated for N2O detection. manufacturer’s recommendations.  Encourage patients to minimize talking ■■ Check both high- and low-pressure ■■ Use scavenging vacuum pumps that are and mouth-breathing during dental surgery. connections (such as O-rings) regularly, powerful enough to maintain a scavenging When mouth-breathing is apparent, avoid the as they may become worn; replace them flow rate of at least 45 L/min at each nasal patient’s breathing zone to the extent possible. periodically, according to the manufacturer’s mask, regardless of the number of scavenging recommendations. units in use at one time. Respiratory protection

■■ Evaluate the N2O and oxygen mixing ■■ Vent N2O from all scavenging vacuum pumps Workers should wear respiratory protection when system for leaks when it is first installed to the outside of the building away from N2O concentrations are not consistently below and periodically thereafter, according to the fresh air intakes, windows or walkways. 25 ppm; however, practical considerations may manufacturer’s recommendations. Scavenging system exhaust should not be prevent them from wearing such protection. ■■ Ensure that gas cylinders are safely handled, vented into a recirculating ventilation system. Therefore, it is essential that employers use the engineering controls and work practices used and stored as specified by the National Room ventilation. Take the following steps to Research Council and as required by OSHA described in a 1994 NIOSH alert to reduce N O assure that the ventilation system effectively 2 concentrations below 25 ppm. Federal Code Rule Title 29, 1910.101. removes waste N O: □□ Sec. 1910.101 Compressed gases 2 ■■ If concentrations of N2O are above 25 ppm in When N2O concentrations are not consistently (general requirements). work areas, increase the airflow into the room below 25 ppm, workers should take the following □□ (a) Inspection of compressed gas or increase the percentage of outside air to steps to protect themselves: cylinders. Each employer shall determine allow for more air mixing and further dilution ■■ Wear air-supplied respirators. Air-purifying that compressed gas cylinders under of the anesthetic gas. Maintain a balanced air respirators (that is, respirators that remove N O his control are in a safe condition to 2 supply and exhaust system so that N2O does from the air rather than supply air from a clean the extent that this can be determined not contaminate adjacent areas. source) should not be used because respirator by visual inspection. Visual and other ■■ If concentrations of N2O are still above 25 filters do not efficiently remove2 N O. inspections shall be conducted as ppm, use supplementary local ventilation ■■ As specified by the NIOSH respirator prescribed in the Hazardous Materials in conjunction with a scavenging system to standards, the minimum level of protection Regulations of the Department of reduce N2O exposure in the operatory. The for an air-supplied respirator is provided by a Transportation (49 CFR parts 171-179 effectiveness of this ventilation depends half-mask respirator operated in the demand and 14 CFR part 103). Where those on its location with respect to the patient or continuous-flow mode. More protective regulations are not applicable, visual and the airflow rates. Do not work between air-supplied respirators are described in the and other inspections shall be conducted the patient and the exhaust duct, where NIOSH respirator decision logic. in accordance with Compressed Gas contaminated air would be drawn through the ■■ When respirators are used, the employer Association Pamphlets C-6-1968 and worker’s breathing zone. must establish a comprehensive respiratory C-8-1962, which is incorporated by ■■ Dilute N2O and remove contaminated air protection program as outlined in the NIOSH reference as specified in Sec. 1910.6. from the work area by placing fresh-air vents Guide to Industrial Respiratory Protection

Scavenging systems. Control of N2O at the in the ceiling; direct the supply of fresh air [NIOSH 1987a] and as required by the scavenging mask is the next priority after control toward the floor and the operating area. Place OSHA respiratory protection standard [29 of N2O leakage from the anesthetic equipment. exhaust-air vents at or near the floor. CFR 1910.134]. Important elements of this Leakage from the scavenging mask can be one standard are: of the most significant sources of 2N O exposure Work practices □□ An evaluation of the worker’s ability to because the breathing zone of a dentist or Use the following work practices to control N2O perform the work while wearing a respirator. dental assistant is within inches of the mask. exposures: □□ Regular training of personnel. NIOSH research has reported breathing-zone ■■ Inspect the anesthetic delivery systems and □□ Periodic environmental monitoring. concentrations of N2O above 1,000 ppm. all connections before starting anesthetic □□ Respirator fit testing. gas administration. Make sure that breathing □□ Maintenance, inspection, cleaning and Take the following steps to control N O exposure 2 bags, hoses and clamps are in place before storage. from anesthetic scavenging systems: turning on the anesthetic machine. □□ Selection of proper NIOSH-approved ■■ Supply scavenging masks in a variety of sizes ■■ Connect the scavenging mask properly to the respirators. so that the mask always fits comfortably and gas delivery hose and the vacuum system. ■■ The respiratory protection program should be securely over the patient’s nose or face. ■■ Do not turn on the machine delivering N O until: evaluated regularly by the employer. ■■ Use an automatic interlock system to assure 2 □□ The vacuum system scavenging unit is that the N O cannot be turned on unless the 2 operating at the recommended flow rate Signs and symptoms of exposure scavenging system is also activated. N O 2 of 45 L/min. ■■ Acute exposure: The signs and symptoms should never be used without a properly □□ The scavenging mask is secured over the of acute exposure to nitrous oxide include operating scavenging system. patient’s nose or face. dizziness, difficult breathing, headache, ■■ Make sure that the scavenging system ■■ Fasten the mask according to the nausea, fatigue and irritability. Acute exposure exhaust rates (flow rates) are approximately manufacturer’s instructions to prevent leaks to nitrous oxide concentrations of 400,000 to 45 liters per minute (L/min) to minimize around the mask during gas delivery. 800,000 ppm may cause loss of consciousness. leakage of N O. Flow rates of less than 40 L/ 2 ■■ Do not fill the breathing bag to capacity with ■■ Chronic exposure: The signs or symptoms min may result in significant leakage around N O; an overinflated bag can cause excessive of chronic overexposure to nitrous oxide the mask. Monitor the flow rate with a flow 2 leakage from the scavenging mask. The may include tingling, numbness, difficulty meter that is: breathing bag should collapse and expand as in concentrating, interference with gait, and □□ Validated to measure airflow within 5 the patient breaths. This bag activity shows reproductive effects. percent of actual airflow.

Elite Page 19 Storage as defined in 40 CFR 261.21-261.24. Under Personal protective equipment Nitrous oxide should be stored in a cool, dry, well- the Resource Conservation and Recovery Workers should use appropriate personal ventilated area in tightly sealed containers that Act (RCRA) [40 USC 6901 et seq.], EPA protective clothing and equipment that must be are labeled in accordance with OSHA’s Hazard has specifically listed many chemical wastes carefully selected, used and maintained to be Communication Standard [29 Code of Federal as hazardous. Although nitrous oxide is not effective in preventing skin contact with liquid Regulations (CFR)1910.1200]. Containers of specifically listed as a hazardous waste under nitrous oxide. The selection of the appropriate nitrous oxide should be protected from physical RCRA, EPA requires employers to treat waste as personal protective equipment (PPE) (e.g., damage and should be stored separately from hazardous if it exhibits any of the characteristics gloves, sleeves, encapsulating suits) should be cylinders containing oxygen. Nitrous oxide discussed above. Providing detailed information based on the extent of the worker’s potential should also be stored separately from aluminum, about the removal and disposal of specific exposure to liquid nitrous oxide and the PPE boron, hydrazine, lithium hydride, phenyllithium, chemicals is beyond the scope of this guideline. material’s ability to protect workers from phosphine, sodium, tungsten carbide, hydrogen, The U.S. Department of Transportation, EPA, and frostbite. There are no published reports on the hydrogen sulfide, organic peroxides, ammonia and state and local regulations should be followed resistance of various materials to permeation by carbon monoxide. to ensure that removal, transport and disposal liquid nitrous oxide. of this substance are conducted in accordance To evaluate the use of PPE materials with liquid Spills and leaks with existing regulations. To be certain that nitrous oxide, users should consult the best In the event of a spill or leak involving nitrous chemical waste disposal meets EPA regulatory available performance data and manufacturers’ oxide (liquid or gas), persons not wearing requirements, employers should address any recommendations. Significant differences have protective equipment and clothing should be questions to the RCRA hotline at (703) 412- been demonstrated in the chemical resistance of restricted from contaminated areas until cleanup 9810 (in the Washington, D.C. area) or toll-free generically similar PPE materials (e.g., butyl) has been completed. The following steps should at 800-424-9346 (outside Washington, D.C.). produced by different manufacturers. In addition, the be undertaken following a spill or leak: In addition, relevant state and local authorities chemical resistance of a mixture may be significantly ■■ Do not touch the spilled material; stop the should be contacted for information on any different from that of any of its neat components. leak if it is possible to do so without risk. requirements they may have for the waste ■■ Use water spray to protect persons attempting removal and disposal of this substance. Any chemical-resistant clothing that is used to stop the leak. should be periodically evaluated to determine its ■■ Notify safety personnel of large spills or leaks. Respiratory protection effectiveness in preventing dermal contact. Safety ■■ Minimize all sources of ignition because a showers and eye wash stations should be located Conditions for respirator use fire may cause nitrous oxide to accelerate close to operations that involve nitrous oxide. Good industrial hygiene practice requires that the burning of other combustibles; keep Splash-proof chemical safety goggles or face combustible materials (wood, paper, oil, etc.) engineering controls be used where feasible to reduce workplace concentrations of hazardous shields (20 to 30 cm long, minimum) should be away from the spilled material. worn during any operation in which a solvent, ■■ Isolate the area until the gas has dispersed. materials to the prescribed exposure limit. However, some situations may require the use caustic or other toxic substance may be splashed into the eyes. Special requirements of respirators to control exposure. Respirators United States Environmental Protection Agency must be worn if the ambient concentration of In addition to the possible need for wearing (EPA) requirements for emergency planning, nitrous oxide exceeds prescribed exposure limits. protective outer apparel (e.g., aprons, reportable quantities of hazardous releases, Respirators may be used (1) before engineering encapsulating suits), workers should wear work community right-to-know and hazardous waste controls have been installed, (2) during work uniforms, coveralls or similar full-body coverings management may change over time. Users are operations such as maintenance or repair that are laundered each day. Employers should therefore advised to determine periodically activities that involve unknown exposures, (3) provide lockers or other closed areas to store whether new information is available. during operations that require entry into tanks work and street clothing separately. Employers or closed vessels, and (4) during emergencies. should collect work clothing at the end of Emergency planning requirements Workers should only use respirators that have each work shift and provide for its laundering. Nitrous oxide is not subject to EPA emergency been approved by NIOSH and the Mine Safety Laundry personnel should be informed about planning requirements under the Superfund and Health Administration (MSHA). the potential hazards of handling contaminated Amendments and Reauthorization Act (SARA) clothing and instructed about measures to (Title III) in 42 CFR 11022. Respiratory protection program minimize their health risk. Employers should institute a complete respiratory Protective clothing should be kept free of oil and Reportable quantity requirements for protection program that, at a minimum, complies with the requirements of OSHA’s Respiratory grease and should be inspected and maintained hazardous releases regularly to preserve its effectiveness. Employers are not required by the emergency Protection Standard [29 CFR 1910.134]. Such release notification provisions in 40 CFR Part a program must include respirator selection, an Protective clothing may interfere with the body’s 355.40 to notify the National Response Center of evaluation of the worker’s ability to perform the work heat dissipation, especially during hot weather an accidental release of nitrous oxide; there is no while wearing a respirator, the regular training of or during work in hot or poorly ventilated work reportable quantity for this substance. personnel, respirator fit testing, periodic workplace environments. monitoring, and regular respirator maintenance, Community right-to-know requirements inspection and cleaning. The implementation of an More on personal protective equipment Employers are not required by EPA in 40 CFR adequate respiratory protection program (including ■■ Personal protective equipment should not be Part 372.30 to submit a Toxic Chemical Release selection of the correct respirator) requires that a used as a substitute for engineering, work Inventory form (Form R) to EPA reporting the knowledgeable person be in charge of the program practice and/or administrative controls in amount of nitrous oxide emitted or released from and that the program be evaluated regularly. For anesthetizing locations and post anesthesia their facility annually. additional information on the selection and use of care units (PACUs). In fact, exposure to waste respirators and on the medical screening of respirator gases is not effectively reduced by gloves, Hazardous waste management requirements users, consult the latest edition of the NIOSH goggles and surgical masks. A negative- EPA considers a waste to be hazardous if it Respirator Decision Logic [NIOSH 1987b] and the pressure, high-efficiency particulate air exhibits any of the following characteristics: NIOSH Guide to Industrial Respiratory Protection (HEPA) filter used for infection control is also ignitability, corrosivity, reactivity or toxicity [NIOSH 1987a]. not appropriate to protect workers from waste

Page 20 Elite gases. Air-supplied respirators with self- Workplace exposures Because pipeline systems can fail and because contained air source are ideal for eliminating Workplace exposures to anesthetic gases occur the machines may be used in locations where exposure but are not a practical alternative. in hospital-based and stand-alone operating piped gases are not available, anesthesia machines ■■ During cleanup and containment of spills of rooms, recovery rooms, dental operatories and are fitted with reserve cylinders of oxygen and

liquid anesthetic agents, personal protective veterinary facilities. Engineering, work practice N2O. The oxygen cylinder source is regulated equipment should be used in conjunction with and administrative controls that help reduce from approximately 2,200 psig in the tanks to engineering, work practice and administrative these exposures in all anesthetizing locations approximately 45 psig in the machine high-pressure

controls to provide for employee safety are identified and discussed. Sources of leaks system, and the N2O cylinder source is regulated and health. Gloves, goggles, face shields in anesthesia equipment systems, components, from 745 psig in the tanks to approximately 45 psig and chemical protective clothing (CPC) are and accessories are identified, and appropriate in the machine high-pressure system. recommended to ensure worker protection. methods are described that limit excessive leaks. Figure 1 (located at end of chapter) Respirators, where needed, should be selected Inhaled anesthetic agents include two different The flow arrangement of a basic two-gas based on the anticipated contamination level. classes of chemicals: nitrous oxide and halogenated anesthesia machine. A, The fail-safe valve in ■■ When selecting gloves and chemical agents. Halogenated agents currently in use include Ohmeda machines is termed a pressure sensor protective clothing, some of the factors to halothane (Fluothane®), enflurane (Ethrane®), shut-off valve; in Dräger machines it is the be considered include material chemical isoflurane (Forane®), desflurane (Suprane®), oxygen failure protection device (OFPD). B, resistance, physical strength and durability, and sevoflurane (Ultane®). Methoxyflurane Second-stage oxygen pressure regulator is used and overall product integrity. Permeation, (Penthrane®), once in general use, is now only in Ohmeda (but not Dräger Narkomed) machines. penetration and degradation data should infrequently used, primarily in veterinary C, Second-stage nitrous oxide pressure regulator be consulted if available. Among the most procedures. At present, OSHA has no permissible is used in Ohmeda Modulus machines having the effective types of gloves and body protection exposure limits regulating these agents. Link 25 Proportion Limiting System; not used in ®, neoprene and are those made from Viton Dräger machines. D, Pressure relief valve used nitrile. Polyvinyl alcohol (PVA) is also The basic anesthesia machine in certain Ohmeda mchines; not used in Dräger effective, but it should not be exposed to An anesthesia machine is an assembly of various machines. E, Outlet check valve used in Ohmeda water or aqueous solutions. components and devices that include medical machines except Modulus II Plus and Modulus ■■ When the gloves and the CPC being used gas cylinders in machine hanger yokes, pressure CD models; not used in Dräger machines. The have not been tested under the expected regulating and measuring devices, valves, flow oxygen take-off for the anesthesia ventilator conditions, they may fail to provide adequate controllers, flow meters, vaporizers, CO absorber driving gas circuit is downstream of the main on/ protection. In this situation, the wearer 2 canisters, and breathing circuit assembly. The off switch in Dräger machines, as shown here. In should observe the gloves and the chemical basic two-gas anesthesia machine has more than Ohmeda machines, the take-off is upstream of the protective clothing during use and treat any 700 individual components. main on/off switch. (Adapted from Check-out: a noticeable change (e.g., color, stiffness, guide for preoperative inspection of an anesthesia chemical odor inside) as a failure until The anesthesia machine is a basic tool of the machine, ASA, 1987. Reproduced by permission proved otherwise by testing. If the work anesthesiologist/anesthetist and serves as the of the American Society of Anesthesiologists, must continue, new CPC should be worn for primary work station. It allows the anesthesia 520 N. Northwest Highway, Park Ridge, Ill.) a shorter exposure time, or be of a different provider to select and mix measured flows of generic material. The same thickness of gases, to vaporize controlled amounts of liquid Figure 2 (located at end of chapter) a generic material such as neoprene or anesthetic agents, and thereby to administer The supply of nitrous oxide and oxygen may nitrile supplied by different manufacturers safely controlled concentrations of oxygen and come from two sources: the wall (pipeline) supply may provide significantly different levels anesthetic gases and vapors to the patient via a and the reserve cylinder supply. (Reproduced of protection because of variations in the breathing circuit. The anesthesia machine also by permission of Datex·Ohmeda, Madison, manufacturing processes or in the raw provides a working surface for placement of Wisconsin). Compressed gas cylinders of oxygen,

materials and additives used in processing. drugs and devices for immediate access and N2O, and other medical gases are attached to ■■ Professional judgment must be used in drawers for storage of small equipment, drugs, the anesthesia machine through the hanger yoke determining the type of respiratory protection supplies and equipment instruction manuals. assembly. Each hanger yoke is equipped with the to be worn. For example, where spills of Finally, the machine serves as a frame and source pin index safety system, a safeguard introduced halogenated anesthetic agents are small, of pneumatic and electric power for various to eliminate cylinder interchanging and the exposure time brief and sufficient ventilation accessories such as a ventilator, and monitors that possibility of accidentally placing the incorrect gas present, NIOSH-approved chemical cartridge observe or record vital patient functions or that are tank in a yoke designed for another gas tank. critical to the safe administration of anesthesia. respirators for organic vapors should provide Figure 3 (located at end of this chapter) shows adequate protection during cleanup activities. the oxygen pathway through the flow meter, the Gas flow in the anesthesia machine and ■■ Where large spills occur and there is agent vaporizer, and the machine piping, and into insufficient ventilation to adequately reduce breathing system the breathing circuit. Oxygen from the wall outlet airborne levels of the halogenated agent, The internal piping of a basic two-gas anesthesia or cylinder pressurizes the anesthesia delivery respirators designed for increased respiratory machine is shown in Figure 1 (located at end of system. Compressed oxygen provides the needed protection should be used. The following this chapter). The machine has many connections energy for a pneumatically powered ventilator, respirators, to be selected for large spills, are and potential sites for leaks. Both oxygen and if used, and it supplies the oxygen flush valve N O may be supplied from two sources (Figure 2, ranked in order from minimum to maximum 2 used to supplement oxygen flow to the breathing respiratory protection: located at end of this chapter): a pipeline supply circuit. Oxygen also “powers” an in-line □□ Any type C supplied-air respirator with a source (central piping system from bulk storage) pressure-sensor shutoff valve (“fail-safe” valve) full facepiece, helmet or hood operated in and a compressed gas cylinder supply source. In for other gases to prevent their administration if continuous-flow mode. hospitals, the pipeline supply source is the primary the O2 supply pressure in the O2 high-pressure □□ Any type C supplied-air respirator with gas source for the anesthesia machine. Pipeline- system falls below a threshold value. a full facepiece operated in pressure- supplied gases are delivered through wall outlets at Oxygen and N O flow from their supply sources demand or other positive-pressure mode. a pressure of 50-55 psig through diameter indexed 2 □□ Any self-contained breathing apparatus safety system (DISS) fittings or through quick- via their flow control valves, flow meters and with a full facepiece operated in pressure- connect couplings that are gas-specific within each common manifold to the concentration-calibrated demand or other positive-pressure mode. manufacturer’s patented system. vaporizer and then via the machine common gas Elite Page 21 outlet to the breathing system. The high pressure 1991). Leakage may originate from both the be made ready for use. All parts of the machine system of the anesthesia machine comprises high-pressure and low-pressure systems of the should be in good working order with all those components from the compressed gas anesthesia or analgesia machine. accessory equipment and necessary supplies supply source to the gas (O and N O) flow on hand. The waste gas disposal system should 2 2 The high-pressure system consists of all piping control valves. The low pressure system of the and parts of the machine that receive gas at be connected, hoses visually inspected for anesthesia machine comprises those components cylinder or pipeline supply pressure. It extends obstructions or kinks, and proper operation downstream of the gas flow control valves. from the high-pressure gas supply (i.e., wall determined. Similarly, the anesthesia breathing system should be tested to verify that it can Once the flows of oxygen, N2O, and other supply or gas cylinder) to the flow control medical gases (if used) are turned on at their flow valves. Leaks may occur from the high-pressure maintain positive pressure. Leaks should be control valves, the gas mixture flows into the connections where the supply hose connects identified and corrected before the system is used. common manifold and through a concentration- to the wall outlet or gas cylinder and where it The ability of the anesthesia system to maintain calibrated agent-specific vaporizer where a potent connects to the machine inlet. Therefore, gas- constant pressure is tested not only for the safety inhaled volatile anesthetic agent is added. The supply hoses should be positioned to prevent of the patient dependent on a generated positive mixture of gases and vaporized anesthetic agent strain on the fittings (ASTM Standard F1161-88; pressure ventilation but also to test for leaks and then exits the anesthesia machine low pressure Dorsch and Dorsch 1994) and constructed from escape of anesthetic gases, which may expose system through the common gas outlet and flows supply-hose materials designed for high-pressure health-care personnel to waste anesthetic gases. to the breathing system. gas flow and minimal kinking (Bowie and General workplace controls Huffman 1985). High-pressure leakage may also The circle system shown in Figure 4 (located at Occupational exposures can be controlled by occur within the anesthesia machine itself. Other end of this chapter) is the breathing system most the application of a number of well-known potential sources of leaks include quick-connect commonly used in operating rooms (ORs). It is principles, including engineering and work fittings, cylinder valves, absent or worn gaskets, so named because its components are arranged practice controls, administrative controls, missing or worn yoke plugs in a dual yoke in a circular manner. The essential components personal protective equipment and monitoring. assembly, and worn hoses. of a circle breathing system (Figure 5, located These principles may be applied at or near at end of this chapter) include a site for inflow The low-pressure system of the anesthesia the hazard source, to the general workplace of fresh gas (common [fresh] gas inlet), a carbon machine (in which the pressure is slightly above environment, or at the point of occupational dioxide absorber canister (containing soda lime atmospheric) consists of components downstream exposure to individuals. Controls applied at or barium hydroxide lime) where exhaled carbon of the flow-control valves. It therefore includes the source of the hazard, including engineering dioxide is absorbed; a reservoir bag; inspiratory the flow meter tubes, vaporizers, common and work practice controls, are generally the and expiratory unidirectional valves; flexible gas outlet and breathing circuit, (i.e., from the preferred and most effective means of control. corrugated breathing tubing; an adjustable common gas outlet to the patient). Low-pressure In anesthetizing locations and PACUs, where pressure-limiting (APL) or “pop-off” valve for system leaks may occur from the connections and employees are at risk of exposure to waste venting excess gas; and a Y piece that connects to components anywhere between the anesthesia gas anesthetic gases, exposure may be controlled a face mask, tracheal tube, laryngeal mask airway flow control valves and the airway. This leakage by some or all of the following: (1) effective (LMA) or other airway management device. may occur from loose-fitting connections, anesthetic gas scavenging systems that remove defective and worn seals and gaskets, worn or excess anesthetic gas at the point of origin; (2) Once inside the breathing system, the mixture of defective breathing bags, hoses, and tubing, effective general or dilution ventilation; (3) good gases and vapors flows to the breathing system’s loosely assembled or deformed slip joints and work practices on the part of the health care inspiratory unidirectional valve, then on toward the threaded connections, and the moisture drainage workers, including the proper use of controls; patient. Exhaled gases pass through the expiratory port of the CO absorber, which may be in the (4) proper maintenance of equipment to prevent unidirectional valve and enter the reservoir bag. 2 “open” position. leaks; and (5) periodic personnel exposure and When the bag is full, excess gas flows through the environmental monitoring to determine the APL (or pop-off) valve and into the scavenging Low-pressure system leaks also may occur at the effectiveness of the overall waste anesthetic gas system that removes the waste gases. On the next gas analysis sensor (i.e., circuit oxygen analyzer) control program. inspiration, gas from the reservoir bag passes and gas sampling site(s), face mask, the tracheal through the carbon dioxide absorber prior to joining tube (especially in pediatric patients where a leak The following is a general discussion the fresh gas from the machine on its way to the is required around the uncuffed tracheal tube), of engineering controls, work practices, patient. The general use of fresh gas flow rates laryngeal mask airway (over the larynx), and administrative controls, and personal protective into anesthetic systems in excess of those required connection points for accessory devices such as equipment that can reduce worker exposure to to compensate for uptake, metabolism, leaks, a humidifier, temperature probe, or positive end- waste anesthetic gases. However, not every control or removal of exhaled carbon dioxide results in expiratory pressure (PEEP) valve. Inappropriate listed in this section may be feasible in all settings. variable volumes of anesthetic gases and vapors installation of a calibrated vaporizer(s) or exiting the breathing system through the APL valve. misalignment of a vaporizer on its manifold can Engineering controls also contribute to anesthetic gas leakage. The collection and disposal of waste anesthetic When an anesthesia ventilator is used, the gases in operating rooms and non-operating room ventilator bellows functionally replaces the circle Minute absorbent particles that may have been settings is essential for reducing occupational system reservoir bag and becomes a part of the spilled on the rubber seal around the absorber exposures. Engineering controls such as an breathing circuit. The APL valve in the breathing canister(s) may also prevent a gas-tight seal appropriate anesthetic gas scavenging system are circuit is either closed or excluded from the circuit when the canister(s) in the carbon dioxide the first line of defense and the preferred method using a manual (“bag”)/automatic (ventilator) absorber is (are) reassembled). The exhaust from of control to protect employees from exposure circuit selector switch. The ventilator incorporates a sidestream sampling respiratory gas analyzer to anesthetic gases. An effective anesthetic gas a pressure-relief valve that permits release of and/or capnograph should also be connected scavenging system traps waste gases at the site of excess anesthetic gases from the circuit at end- to the waste gas scavenging system because overflow from the breathing circuit and disposes exhalation. These gases should also be scavenged. the analyzed gas sample may contain N2O or of these gases to the outside atmosphere. The halogenated vapors. heating, ventilating and air conditioning (HVAC) Sources of leaks within the anesthesia system also contributes to the dilution and removal machine and breathing system Checking anesthesia machines of waste gases not collected by the scavenging No anesthesia machine system is totally leak- Prior to induction of anesthesia, the anesthesia system or from other sources such as leaks in the free (Emergency Care Research Institute machine and its components/accessories should anesthetic apparatus or improper work practices.

Page 22 Elite The exhalation of residual gases by patients in the from the breathing circuit until it reaches the gas an arrangement that transfers waste gases into the PACU may result in significant levels of waste disposal assembly. ventilation system at a safe distance downstream anesthetic gases when appropriate work practices from the point of recirculation to ensure that the are not used at the conclusion of the anesthetic Active systems anesthetic gases will not be circulated elsewhere or inadequate ventilation exists in the PACU. A Excess anesthetic gases may be removed by within the building. a central vacuum system (servicing the ORs nonrecirculating ventilation system can reduce Under certain circumstances, a separate duct in general) or an exhaust system dedicated to waste gas levels in this area. Waste gas emissions for venting anesthetic gases directly outside the disposal of excess gases. When the waste to the outside atmosphere must meet local, state, the building without the use of a fan may be an anesthetic gas scavenging system is connected and Environmental Protection Agency (EPA) acceptable alternative. By this technique, excess to the central vacuum system (which is shared regulatory requirements. anesthetic gases may be vented through the by other users, e.g., surgical suction), exposure A scavenging system consists of five basic wall, window, ceiling or floor, relying only on levels may be effectively controlled. The central components (ASTM, F 1343 - 91): the slight positive pressure of the gases leaving vacuum system must be specifically designed ■■ A gas collection assembly, such as a collection the gas collection assembly to provide the flow. to handle the large volumes of continuous manifold or a distensible bag (i.e., Jackson- However, several limitations are apparent. A suction from OR scavenging units. If a central Rees pediatric circuit), which captures excess separate line would be required for each OR to vacuum system is used, a separate, dedicated gas anesthetic gases at the site of emission, and prevent the cross-contamination with anesthetic disposal assembly tubing should be used for the delivers it to the transfer tubing. gases among the ORs. A safe disposal site would scavenging system, distinct from the tubing used ■■ Transfer tubing, which conveys the excess be necessary. The possible effects of variations for patient suctioning (used for oral and nasal anesthetic gases to the interface. in wind velocity and direction would require gastric sources as well as surgical suctioning). ■■ The interface, which provides positive a means for preventing a reverse flow in the (and sometimes negative) pressure relief Similarly, when a dedicated exhaust system disposal system. Occlusion of the outer portion of and may provide reservoir capacity. It is (low velocity) is used, excess gases can also be such a passive system by ice or by insect or bird designed to protect the patient’s lungs from collected from one or more ORs and discharged nests is also possible. The outside opening of a excessive positive or negative scavenging to the outdoors. The exhaust fan must provide through-wall, window, ceiling or floor disposal system pressure. sufficient negative pressure and air flow so that assembly should be directed downward, shielded ■■ Gas disposal assembly tubing, which cross-contamination does not occur in the other and screened to prevent the entrance of foreign conducts the excess anesthetic gases from the ORs connected to this system. Active systems matter or ice buildup. Despite these limitations, interface to the gas disposal assembly. are thought to be more effective than passive the separate duct without the use of a fan may be ■■ The gas disposal assembly, which conveys systems at reducing excess waste anesthetic gas ideal in older facilities constructed with windows the excess gases to a point where they can concentrations because leaks in the scavenging that cannot be opened and in the absence of be discharged safely into the atmosphere. system do not result in an outward loss of gas. nonrecirculating air conditioning. Several methods in use include a Passive systems Absorbers can also trap most excess anesthetic nonrecirculating or recirculating ventilation gases. Canisters of varying shapes and capacities HVAC systems used in health-care facilities are system, a central vacuum system, a dedicated filled with activated charcoal have been used as of two types: nonrecirculating and recirculating. (single-purpose) waste gas exhaust system, a waste gas disposal assemblies by directing the Nonrecirculating systems, also termed “one-pass” passive duct system and an adsorber. gases from the gas disposal tubing through them. or “single-pass” systems, take in fresh air from In general, a machine-specific interface must be Activated charcoal canisters will effectively the outside and circulate filtered and conditioned integrated with a facility’s system for gas removal. adsorb the vapors of halogenated anesthetics, but air (i.e., controlled for temperature and humidity) The interface permits excess gas to be collected in not N O. The effectiveness of individual canisters through the room. Whatever volumes of fresh 2 a reservoir (bag or canister) and limits the pressure and various brands of charcoal vary widely. air are introduced into the room are ultimately within the bag or canister. A facility’s gas disposal Different potent inhaled volatile agents are exhausted to the outside. Waste anesthetic system receives waste anesthetic gases from the adsorbed with varying efficiencies. The efficiency gases can be efficiently disposed of via this interface and should vent the waste gases outside of adsorption also depends on the rate of gas flow nonrecirculating system. the building and away from any return air ducts or through the canister. The canister is used where open windows, thus preventing the return of the When a nonrecirculating ventilation system portability is necessary. The disadvantages are waste gases back into the facility. serves through large-diameter tubing and that they are expensive and must be changed terminating the tubing at the room’s ventilation frequently. Canisters must be used and discarded Removal of excess anesthetic gases from the exhaust as the disposal route for excess anesthetic in the appropriate manner, as recommended by anesthesia circuit can be accomplished by either gases, disposal involves directing the waste gases the manufacturer. active or passive scavenging. When a vacuum or grille. The sweeping effect of the air flowing into source of negative pressure is connected to the the grille carries the waste gases away. Because General or dilution ventilation scavenging interface, the system is described as all of the exhausted air is vented to the external An effective room HVAC system when used in an active system. When a vacuum or negative atmosphere in this type of system, the excess combination with an anesthetic gas scavenging pressure is not used, the system is described as anesthetic gases can be deposited into the exhaust system should reduce, although not entirely a passive system. With an active system, there stream either at the exhaust grille or further eliminate, the contaminating anesthetic gases. If will be a negative pressure in the gas disposal downstream in the exhaust duct. excessive concentrations of anesthetic gases are tubing. With a passive system, this pressure will present, then airflow should be increased in the be increased above atmospheric (positive) by the Concern for fuel economy has increased the use of room to allow for more air mixing and further patient exhaling passively, or manual compression systems that recirculate air. Recirculating HVAC/ dilution of the anesthetic gases. Supply register of the breathing system reservoir bag. ventilation systems return part of the exhaust air back into the air intake and recirculate the mixture louvers located in the ceiling should be designed Use of a central vacuum system is an example of through the room. Thus, only a fraction of the to direct the fresh air toward the floor and toward an active system: The waste anesthetic gases are exhaust air is disposed of to the outside. To maintain the health care workers to provide dilution and moved along by negative pressure. Venting waste minimal levels of anesthetic exposure, air that is to removal of the contaminated air from the operatory anesthetic gas via the exhaust grille or exhaust be recirculated must not contain anesthetic gases. or PACU. Exhaust register louvers should be duct of a nonrecirculating ventilation system is an Consequently, recirculating systems employed as a properly located (usually low on the wall near the example of a passive system: The anesthetic gas disposal pathway for waste anesthetic gases must floor level) in the room to provide adequate air is initially moved along by the positive pressure not be used for gas waste disposal. The exception is distribution. They should not be located near the Elite Page 23 supply air vents because this will short-circuit the waste gas exposure. It is, therefore, important using conventional time-weighted average air airflow and prevent proper air mixing and flushing for this group of workers to do the following: sampling or real-time air sampling techniques. of the contaminants from the room. □□ Monitor airborne concentrations of waste ■■ Encourage or promote the use of scavenging gases by sampling, measuring, and reporting systems in all anesthetizing locations where Work practices data to the institution’s administration. Air inhaled agents are used, recognizing that a waste Work practices, as distinct from engineering monitoring for waste anesthetic gases should gas scavenging system is the most effective controls, involve the way in which a task is include both personal sampling (i.e., in a means of controlling waste anesthetic gases. performed. OSHA has found that appropriate health-care worker’s breathing zone) and ■■ Implement an information and training work practices can be a vital aid in reducing the area sampling. program for employees exposed to anesthetic exposures of OR personnel to waste anesthetic □□ Assist in identifying sources of waste/ agents that complies with OSHA’s Hazard agents. In contrast, improper anesthetizing leaking gases and implementing Communication Standard (29 CFR 1910.1200) techniques can contribute to increased waste corrective action. so that employees can meaningfully participate gas levels. These techniques can include an □□ Determine whether the scavenging in, and support, the protective measures improperly selected and fitted face mask, an system is designed and functioning instituted in their workplace. insufficiently inflated tracheal tube cuff, an properly to remove the waste anesthetic ■■ Define and implement appropriate work improperly positioned laryngeal mask, or other gases from the breathing circuit, and practices to help reduce employee exposure. airway, and careless filling of vaporizers and ensure that the gases are vented from Training and educational programs covering spillage of liquid anesthetic agents. the workplace in such a manner that appropriate work practices to minimize General work practices recommended for occupational re-exposure does not occur levels of anesthetic gases in the operating anesthetizing locations include the following: (e.g., smoke trail tests of exhaust grilles room should be conducted at least annually. ■■ A complete anesthesia apparatus checkout used with passive scavenging systems). Employers should emphasize the importance procedure should be performed each day □□ Ensure that operatory and PACU of implementing these practices and should before the first case. An abbreviated version ventilation systems provide sufficient ensure that employees are properly using the should be performed before each subsequent room air exchange to reduce ambient appropriate techniques on a regular basis. case. The FDA Anesthesia Apparatus waste gas levels. ■■ Implement a medical surveillance program Checkout Recommendations should be for all workers exposed to waste gases. Administrative controls considered in developing inspection and ■■ Ensure the proper use of personal protective Administrative controls represent another testing procedures for equipment checkout equipment during cleanup and containment of approach for reducing worker exposure to waste prior to administering an anesthetic. major spills of liquid anesthetic agents. gases other than through the use of engineering ■■ If a face mask is to be used for administration ■■ Manage disposal of liquid agents, spill controls, work practices, or personal protective of inhaled anesthetics, it should be available containment, and air monitoring for waste equipment. Administrative controls may be in a variety of sizes to fit each patient gases following a spill. thought of as any administrative decision that properly. The mask should be pliable and ■■ Comply with existing federal, state, and results in decreased anesthetic-gas exposure. For provide as effective a seal as possible against local regulations and guidelines developed workers potentially exposed to waste anesthetic leakage into the surrounding air. to minimize personnel exposure to waste gases, the program administrator should establish ■■ Tracheal tubes, laryngeal masks, and other anesthetic gases, including the proper and implement policies and procedures to: airway devices should be positioned precisely disposal of hazardous chemicals. ■■ Institute a program of routine inspection and and the cuffs inflated adequately. regular maintenance of equipment in order to Location-specific workplace controls ■■ Vaporizers should be filled in a well-ventilated reduce anesthetic gas leaks and to have the best This section describes engineering and work practice area and in a manner to minimize spillage of performance of scavenging equipment and room controls specific to hospital ORs, PACUs, dental the liquid agent. This can be accomplished ventilation. Preventive maintenance should be operatories and veterinary clinics and hospitals. by using a specialized “key-fill” spout to performed by trained individuals according Operational procedures relating to engineering pour the anesthetic into the vaporizer instead to the manufacturer’s recommendations and controls are also discussed where appropriate. of pouring from a bottle into a funnel-fill at intervals determined by equipment history vaporizer. When feasible, vaporizers should and frequency of use. Preventive maintenance Hospital operating rooms be filled at the location where the anesthetic includes inspection, testing, cleaning, lubrication For years, anesthesia providers tolerated exposure will be administered and, when filled and adjustment of various components. Worn or to waste anesthetic gases and regarded it as an electively, with the fewest possible personnel damaged parts should be repaired or replaced. inevitable consequence of their work. Since the present in the room. Vaporizers should be Such maintenance can result in detection of 1970s, anesthesiologists have steadily worked turned off when not in use. deterioration before an overt malfunction occurs. to improve equipment and technique to reduce ■■ Spills of liquid anesthetic agents should be Documentation of the maintenance program workplace exposures to waste anesthetic gases, cleaned up promptly. should be kept indicating the nature and date of and significant progress has been made. In early ■■ Before extubating the patient’s trachea the work performed, as well as the name of the delivery equipment, waste gases were exhausted or removing the mask or other airway trained individual servicing the equipment. through the APL or “pop-off” valve into the face management device, one should administer ■■ Implement a monitoring program to measure of the anesthesia provider and were distributed non-anesthetic gases/agents so that the airborne levels of waste gases in the breathing into the room air. Present practice, which utilizes washed-out anesthetic gases can be removed zone or immediate work area of those most an efficient scavenging system, avoids this type by the scavenging system. The amount of heavily exposed (e.g., anesthesiologist, nurse of contamination by collecting the excess gases time allowed for this should be based on anesthetist, oral surgeon) in each anesthetizing immediately at the APL valve. clinical assessment and may vary from location and PACU. Periodic monitoring patient to patient. When possible, flushing of (preferably at least semiannually) of waste Engineering controls the breathing system should be achieved by gas concentrations is needed to ensure that the Waste gas evacuation is required for every type of exhausting into the scavenging system rather anesthesia delivery equipment and engineering/ breathing circuit configuration with the possible than into the room air. environmental controls work properly and exception of a closed circuit, because most anesthesia ■■ Work practices performed by biomedical that the maintenance program is effective. techniques typically use more fresh gas flow than is engineers and technicians also contribute Monitoring may be performed effectively required. Appropriate waste gas evacuation involves significantly to the efficacy of managing collection and removal of waste gases, detection and

Page 24 Elite correction of leaks, consideration of work practices, more difficult to control health-care workers’ and sedatives for more than 100 years. The usual and effective room ventilation. To minimize waste exposures to waste anesthetic gases. The unique analgesia equipment used by dentists includes a anesthetic gas concentrations in the operating room, PACU environment coupled with the patient’s N2O and O2 delivery system, a gas mixing bag the recommended air exchange rate (room dilution immediate condition upon arrival from surgery and a nasal mask with a positive pressure relief ventilation) is a minimum total of 15 air changes per require different work practices than those valve. The analgesia machine is usually adjusted hour with a minimum of 3 air changes of outdoor air routinely used in ORs. Patients undergoing to deliver more of the analgesic gas mixture than (fresh air) per hour. Operating room air containing general anesthesia usually have their airways the patient can use. waste anesthetic gases should not be recirculated to secured using a tracheal tube with an inflatable Analgesia machines for dentistry are designed the operating room or other hospital locations. cuff that seals the tube within the trachea. The to deliver up to 70 percent (700,000 ppm) N2O seal between the tracheal tube cuff and the to a patient during dental surgery. The machine Work practices trachea (or between the face mask and the face) restricts higher concentrations of N O from being In most patients, a circle absorption system is 2 is essential for maintaining a gas-tight system administered to protect the patient from hypoxia. used and can be easily connected to a waste that permits effective scavenging in the OR. In most cases, patients receive between 30 and gas scavenging system. In pediatric anesthesia, The tracheal tube connects the patient with 50 percent N O during surgery. The amount of systems other than those with a circle absorber 2 the breathing circuit that is connected to the time N O is administered to a patient depends on may be used. Choice of the breathing circuit that 2 scavenging system in the OR. Once the patient the dentist’s judgment of patient needs and the best meets the needs of pediatric patients may reaches the PACU, scavenging systems such as complexity of the surgery. The most common alter a clinician’s ability to scavenge waste gas those used in the OR are no longer effective, route of N O delivery and exhaust is through a effectively. Breathing circuits frequently chosen 2 since the patient is no longer connected to the nasal scavenging mask applied to the patient. for neonates, infants and small children are breathing circuit. Other less-effective methods of usually valveless, have low resistance and limit waste gas removal are thus relied upon. Some dentists administer N2O at higher rebreathing. The Mapleson D system and the concentrations at the beginning of the operation, then Jackson-Rees modification of the Ayre’s T-piece Engineering controls decrease the amount as the operation progresses. are examples of limited rebreathing systems that As a result of using appropriate anesthetic gas Others administer the same amount of N2O require appropriate scavenging equipment. scavenging in ORs, the levels of contamination throughout the operation. When the operation is completed, the N O is turned off. Some dentists turn The following work practices may be employed have been decreased. In the PACU, however, 2 the N O on only at the beginning of the operation, with any of the above breathing circuits: the principle of scavenging as practiced in 2 using N O as a sedative during the administration ■■ Empty the contents of the reservoir bag the OR is not widely accepted due to medical 2 of local anesthesia, and turn it off before operating directly into the anesthetic gas scavenging considerations and consequently is infrequently procedures. Based on variations in dental practices system and turn off the flow of N O and employed as a source-control method for 2 and other factors in room air, N O concentrations can any halogenated anesthetic agent prior to preventing the release of waste anesthetic gases 2 vary considerably for each operation and also vary disconnecting the patient circuit. into the PACU environment. Most PACUs provide care to multiple patients in beds without over the course of the operation. ■■ Turn off the flow of N2O and the vaporizer, if appropriate, when the patient circuit is walls between them, and convective currents Unless the procedure is performed under general disconnected from the patient, for example, move the gases from their source to other areas. anesthesia in an OR, halogenated anesthetics are for oral or tracheal suctioning. Therefore, in the PACU, a properly designed not administered, nor does the patient undergo ■■ Test daily for low-pressure leaks throughout and operating dilution ventilation system should laryngoscopy and tracheal intubation. In the the entire anesthesia system. All leaks be relied upon to minimize waste anesthetic gas typical dental office procedure, the nasal mask is should be minimized before the system is concentrations. This system should provide a placed on the patient, fitted and adjusted prior to used. Starting anesthetic gas flow before the recommended minimum total of 6 air changes per administration of the anesthetic agent. The mask actual induction of anesthesia begins is not hour with a minimum of 2 air changes of outdoor is designed for the nose of the patient because acceptable. For techniques to rapidly induce air per hour to adequately dilute waste anesthetic access to the patient’s mouth is essential for anesthesia using inhaled agents (single-breath gases. Room exhaust containing waste anesthetic dental procedures. mask induction), the patient connector should gases should not be recirculated to other areas of the hospital. A local anesthetic, if needed, is typically be occluded when filling the breathing circuit administered after the N O takes effect. The with nitrous oxide or halogenated agent prior 2 Work practices patient’s mouth is opened and the local anesthetic to applying the mask to the patient’s face. PACU managers should consider: is injected. The dental procedure begins after If the circle absorber system (Figure 6 - located ■■ Periodic exposure monitoring with particular the local anesthetic takes effect. The patient at end of this chapter) is used, the following emphasis on peak gas levels in the breathing opens his/her mouth but is instructed to breathe additional work practices can be employed: zone of nursing personnel working in the through the nose. Nonetheless, a certain amount ■■ Adjust the vacuum needle valve as needed immediate vicinity of the patient’s head. of mouth breathing frequently occurs. The dentist to regulate the flow of waste anesthetic Methods using random room sampling to assess may periodically stop the dental procedure for a gases into the vacuum source in an active ambient concentrations of waste anesthetic moment to allow the patient to close the mouth scavenging system. Adjustments prevent the gases in the PACU are not an accurate indicator and breathe deeply to re-establish an appropriate bag from overdistending by maintaining the of the level of exposure experienced by concentration of N2O in the patient’s body before volume in the scavenging system reservoir nurses providing bedside care. Because of the resuming the procedure. Depending on the bag between empty and half-full. In machines closeness of the PACU nurse to the patient, nature of the procedure, high velocity suction that use an open reservoir to receive waste such methods would consistently underestimate is regularly used to remove intraoral debris gas, a flow meter is used to adjust the rate of the level of waste anesthetic gases in the and, when used, creates a negative air flow and gas flow to the vacuum system. breathing zone of the bedside nurse. captures some of the gas exhaled by the patient. ■■ Cap any unused port in a passive waste gas ■■ Application of a routine ventilation system At the end of the procedure, the nosepiece is left scavenging configuration. maintenance program to keep waste gas on the patient while the N2O is turned off and the exposure levels to a minimum. oxygen flow is increased. The anesthetic mixture Postanesthesia care in hospitals and diffuses from the circulating blood into the lungs stand-alone facilities Dental operatory and is exhaled. Scavenging is continued while the Because the patient is the main source of waste Mixtures of N O and oxygen have been used in 2 patient is eliminating the N2O. anesthetic gases in the PACU, it becomes dentistry as general anesthetic agents, analgesics

Elite Page 25 The dental office or operatory should have a solution may be used to test for leaks at Because of the volatility of liquid anesthetics, properly installed N2O delivery system. This connections. Alternatively, a portable infrared rapid removal by suctioning in the OR is the includes appropriate scavenging equipment with spectrophotometer can be used to detect an preferred method for cleaning up spills. Spills a readily visible and accurate flow meter (or insidious leak. of large volumes in poorly ventilated areas or equivalent measuring device), a vacuum pump ■■ Prior to first use each day, inspect all 2N O in storage areas should be absorbed using an with the capacity for up to 45 L/min of air per equipment (e.g., reservoir bag, tubing, mask, absorbent material, sometimes called a sorbent, workstation, and a variety of sizes of masks to connectors) for worn parts, cracks, holes, or that is designed for cleanup of organic chemicals. ensure proper fit for individual patients. tears. Replace as necessary. “Spill pillows” commonly used in hospital ■■ Connect mask to the tubing and turn on laboratories, vermiculite, and carbon-based A common nasal mask, shown in Figure 7 (located vacuum pump. Verify appropriate flow sorbents are some of the materials commercially at the end of this chapter), consists of an inner rate (i.e., up to 45 L/min or manufacturer’s available and regularly used for this purpose. and a slightly larger outer mask component. recommendations). Caution should be exercised if broken glass The inner mask has two hoses connected that ■■ A properly sized mask should be selected and bottles pose a hazard. supply anesthetic gas to the patient. A relief placed on the patient. A good, comfortable fit valve is attached to the inner mask to release Both enflurane and desflurane are considered should be ensured. The reservoir (breathing) excess N2O into the outer mask. The outer mask hazardous wastes under the EPA regulations has two smaller hoses connected to a vacuum bag should not be over- or underinflated because these chemicals contain trace amounts of system to capture waste gases from the patient while the patient is breathing oxygen (before chloroform (a hazardous substance), a byproduct administering N O). and excess gas supplied to the patient by the 2 of the manufacturing process. Consequently, ■■ Encourage the patient to minimize talking, analgesia machine. The nasal mask should fit over sorbents that have been saturated with enflurane or mouth breathing and facial movement while the patient’s nose as snugly as possible without desflurane should be managed as an EPA hazardous the mask is in place. impairing the vision or dexterity of the dentist. waste material due to the trace concentrations of ■■ During N O administration, the reservoir bag Gases exhaled orally are not captured by the nasal 2 chloroform present. Isoflurane and halothane do not should be periodically inspected for changes mask. A flow rate of approximately 45 L/min has contain trace amounts of chloroform or any other in tidal volume, and the vacuum flow rate been recommended as the optimum rate to prevent regulated substance and are therefore not considered should be verified. significant N O leakage into the room air. hazardous wastes by EPA. 2 ■■ On completing anesthetic administration and A newer type of mask is a frequent choice in dental before removing the mask, non-anesthetic To minimize exposure to all liquid anesthetic practice, a single-patient-use nasal hood. This mask gases/agents should be delivered to the agents during cleanup and to limit exposure does not require sterilization after surgery because it patient for a sufficient time based on clinical during disposal procedures, the following general is used by only one patient and is disposable. assessment that may vary from patient to guidelines are recommended. The waste material should be placed in a container, tightly sealed, In a dental operatory, a scavenging system is part patient. In this way, both the patient and the properly labeled, and disposed of with other of a high-volume evacuation system used with a system will be purged of residual N2O. Do chemical wastes sent to a facility’s incinerator or dental unit. The vacuum system may dispose of a not use an oxygen flush. removed by a chemical waste contractor. After combination of waste gases, oral fluid and debris, a large spill has occurred and the appropriate and is not limited to waste gas removal. The Cleanup and disposal of liquid anesthetic response action taken, airborne monitoring exhaust air of the evacuation system should be agent spills should be conducted to determine whether the vented outside the building and away from fresh- Small volumes of liquid anesthetic agents such spill was effectively contained and cleaned up. air inlets and open windows to prevent re-entry of as halothane, enflurane, isoflurane, desflurane, gas into the operatory. and sevoflurane evaporate readily at normal Determination of appropriate disposal procedures room temperatures, and may dissipate before for each facility is the sole responsibility of The general ventilation should provide good any attempts to clean up or collect the liquid are that facility. Empty anesthetic bottles are not room air mixing. In addition, auxiliary (local) initiated. However, when large spills occur, such as considered regulated waste and may be discarded exhaust ventilation used in conjunction with when one or more bottles of a liquid agent break, with ordinary trash or recycled. Furthermore, the a scavenging system has been shown to be specific cleaning and containment procedures are facility as well as the waste handling contractor effective in reducing excess N O in the breathing 2 necessary and appropriate disposal is required. The must comply with all applicable federal, state, zone of the dentist and dental assistant, from recommendations of the chemical manufacturer’s and local regulations. nasal mask leakage and patient mouth breathing. material safety data sheet (MSDS) that identify This type of ventilation captures the waste exposure reduction techniques for spills and To minimize exposure to waste liquid anesthetic anesthetic gases at their source. However, there emergencies should be followed. agents during cleanup and disposal, the following are practical limitations in using it in the dental general guidelines are recommended by the operatory. These include proximity to the patient, In addition, OSHA Standard for Hazardous Waste manufacturers of liquid anesthetic agents: interference with dental practices, noise, and Operations and Emergency Response would ■■ Wear appropriate personal protective installation and maintenance costs. It is most apply if emergency response efforts are performed equipment. Where possible, ventilate area of important that the dentist not work between the by employees. The employer must determine spill or leak. Appropriate respirators should patient and a free-standing local exhaust hood. the potential for an emergency in a reasonably be worn. Doing so will cause the contaminated air to predictable worst-case scenario, and plan response ■■ Restrict persons not wearing protective be drawn through the dentist’s breathing zone. procedures accordingly. Only adequately trained equipment from areas of spills or leaks until These auxiliary ventilation systems are not now and equipped workers may respond to spills. cleanup is complete. commercially available. The Academy of General When the situation is unclear or data are lacking ■■ Collect the liquid spilled and the absorbent Dentistry also emphasizes properly installed and on the exposure level, the response needs to be the materials used to contain a spill in a glass maintained analgesia delivery systems. same as for high levels of exposure. Responses or plastic container. Tightly cap and seal to incidental releases of liquid anesthetic agents the container and remove it from the Work practices where the substance can be absorbed, neutralized anesthetizing location. Label the container or otherwise controlled at the time of release by ■■ Prior to first use each day of the 2N O machine clearly to indicate its contents. and every time a gas cylinder is changed, the employees in the immediate release area, or by ■■ Transfer the sealed containers to the waste low-pressure connections should be tested maintenance personnel do not fall within the scope disposal company that handles and hauls for leaks. High-pressure line connections of this standard. waste materials. should be tested for leaks quarterly. A soap

Page 26 Elite ■■ Health-care facilities that own or operate The OSHA Chemical Information Manual contains includes the areas of the patient, operating table, medical waste incinerators may dispose of current sampling technology for several of the and furniture covered with sterile drapes and the waste anesthetics by using an appropriate anesthetic gases that may be present in anesthetizing personnel wearing sterile attire. Sampling in the incineration method after verifying that locations and PACUs. Some of the sampling breathing zone of surgeons and other nursing or individual incineration operating permits allow methods available are summarized below. technical personnel who work in the sterile field burning of anesthetic agents at each site. must conform to the principles of sterile field Time-integrated sampling access. Strict adherence to sound principles of Air monitoring ■■ Nitrous oxide sterile technique and recommended practices is Air monitoring is one of the fundamental Personal N2O exposures can be determined mandatory for the safety of the patient. by using the VAPOR-TRAK nitrous oxide tools used to evaluate workplace exposures. Generally speaking, each hospital has its own passive monitor (sometimes called a Accordingly, this section presents some of the guidelines for proper OR attire and other safety “passive dosimeter” or “diffusive sampler”) appropriate methods that can be used to detect procedures. These rules should be strictly as referenced in the 2000 OSHA Chemical and measure the concentration of anesthetic followed by anyone entering the OR. There are Information Manual under IMIS:1953. gases that may be present in the health care standard uniform guidelines that apply to all The minimum sampling duration for the environment. The data provided by monitoring hospitals. Only clean and/or freshly laundered dosimeter is 15 minutes; however, it can be are necessary to establish proper engineering, OR attire is worn in the OR. Proper attire consists used for up to 16 hours of passive sampling. work practice, and administrative controls to of body covers such as a two-piece pantsuit This sampler has not been validated by ensure the lowest reasonably achievable gas (scrub suit), head cover (cap or hood), mask, OSHA. Other dosimeters are commercially levels in the operatory and PACU room air. and shoe covers. A sterile gown is worn over the available and can be used. Although not scrub suit to permit the wearer to come within OSHA recommends that air sampling for anesthetic validated by OSHA at this time, they may the sterile field. Other attire such as gloves and gases be conducted every six months to measure be validated in the future. Five liter, 5-layer eyewear may be required. Some hospitals, but worker exposures and to check the effectiveness of aluminized gas sampling bags can also be not all, may allow persons coming into the OR control measures. Furthermore, OSHA recommends used to collect a sample. to wear a clean gown (in addition to the cap, that only the agents most frequently used need to be ■■ Halogenated agents the mask, and the shoe covers) over their street monitored, since proper engineering controls, work Three chlorofluorocarbon-based anesthetic clothes if they are not going to remain in the OR practices and control procedures should reduce agents (halothane, enflurane, and isoflurane) for longer than 10-15 minutes. all agents proportionately. However, the decision and one fluorocarbon-based agent to monitor only selected agents could depend (desflurane) are listed in the Chemical In regard to decontaminating outside equipment, not only on the frequency of their use, but on the Information Manual. The OSHA sampling each hospital has its own policy. However, the availability of an appropriate analytical method procedure for halothane is listed under common practice is to “wipe off” all surfaces and the cost of instrumentation. ASA emphasizes IMIS:0395; for enflurane, under IMIS:1038; with a chemical disinfectant. Most hospitals use regular maintenance of equipment and scavenging for isoflurane, under IMIS:F118; and for Wescodyne or other phenolic solutions. Good systems, daily check-out procedures for anesthesia desflurane, under IMIS:R218. physical cleaning before disinfection helps equipment, and education to ensure use of reduce the number of microorganisms present The current recommended media sampling for appropriate work practices. It does not believe that a and enhances biocidal action. routine monitoring program is necessary when these halothane, enflurane and isoflurane requires actions are being carried out. ASA prefers to use an Anasorb 747 tube (140/70 mg sections) or Any person not familiar with the OR is usually monitoring when indicated, such as in the event of an Anasorb CMS tube (150/75 mg. sections). instructed by a scrub nurse on all the safety known or suspected equipment malfunction. The sample can be taken at a flow rate of 0.5 procedures pertaining to the hospital. The scrub L/min. Total sample volumes not exceeding nurse will also provide instructions on hand Three fundamental types of air samples can 12 liters are recommended. The current scrubbing and other procedures that may be be taken in order to evaluate the workplace: recommended sampling media for desflurane necessary. Persons entering the OR must follow personal, area and source samples. Personal requires an Anasorb 747 tube (140/70 mg these guidelines and instructions. samples give the best estimate of a worker’s sections). The sample can be taken at a flow exposure level because they represent the In addition, it should be recognized that the patient’s rate of 0.05 L/min. Total sample volumes not welfare, safety, and rights of privacy are paramount. actual airborne contaminant concentration exceeding 3 liters are recommended. All four in the worker’s breathing zone during the sampling methodologies are fully validated Hazard communication sampling period. This is the preferred method analytical procedures. In accordance with the Hazard Communication for determining a worker’s time-weighted Standard (29 CFR 1910,1200), employers in average (TWA) exposure and should be used Real-time sampling health care facilities must develop, implement to assess personal exposures during anesthetic Sampling that provides direct, immediate, and and maintain at the workplace a written, administration and in the PACU. Where several continuous (real-time) readout of anesthetic gas comprehensive hazard communication program health care workers perform the same job, on concentrations in ambient air utilizes a portable that includes provisions for container labeling, the same shift, and in the same work area, and infrared spectrophotometer. Since this method collection and availability of material safety data the length, duration, and level of waste gas provides continuous sampling and instantaneous sheets (MSDSs), and an employee training and exposures are similar, an employer may sample a feedback, sources of anesthetic gas leakage information program. The standard also requires representative fraction of the employees instead and effectiveness of control measures can be a list of hazardous chemicals in the workplace as of all employees. immediately determined. part of the written hazard communication program. Area sampling is useful for evaluating overall Additional sampling guidelines Any chemicals subject to the labeling air contaminant levels in a work area and for requirements of the FDA are exempt from If it should ever be necessary to enter an operating investigating cross-contamination with other areas the labeling requirements under the Hazard room to conduct air sampling, the following in the health care facility. Source sampling can be Communication Standard. This includes such guidelines provide the information needed. used to detect leaks in the anesthesia delivery and chemicals as volatile liquid anesthetics and Individuals performing air sampling should be scavenging systems as well as ineffective capture compressed medical gases. However, containers familiar with and follow all OR procedures for by the scavenging system. Thus, how samples are of other chemicals not under the jurisdiction access into and out of the surgical suite with taken is a critical point in any safety program. of the FDA must be labeled, tagged or marked particular attention to sterile and nonsterile areas. with the identity of the material and must show The patient is the center of the sterile field, which Elite Page 27 appropriate hazard warnings as well as the to provide protection such as engineering 3 Select scavenging Provide a range name and address of the chemical manufacturer, controls, appropriate work practices, emergency system and mask. of mask sizes importer, or other responsible party. The hazard procedures for spill containment, and the use of Mask should for patients. warning can be any type of message – words, personal protective equipment. come in various Check to see pictures, or symbols – that conveys the hazards ■■ Methods and observations that may be used to sizes to patients. that noise levels of the chemical(s) in the container. Labels must detect the presence or release of anesthetic gases Scavenging at the mask are be legible, in English (plus other languages if and other hazardous chemicals in the work area systems should acceptable when desired), and prominently displayed. (such as monitoring conducted by the employer, operate at air flow the scavenging Each MSDS must be in English, although continuous monitoring devices, and the rate of 45 lpm. system exhaust the employer may maintain copies in other appearance or odor of chemicals when released). rate is operated at languages as well, and must include information Personnel training records are not required to 45 lpm. regarding the specific chemical identity of the be maintained, but such records would assist 4 Connect mask to Determine proper anesthetic gases or hazardous chemical and employers in monitoring their programs to ensure hose and turn on vacuum pump size its common names. In addition, information that all employees are appropriately trained. vacuum pump for maintaining must be provided on the physical and chemical Employers can provide employees information before turning on 45 lpm flow rates, characteristics of the hazardous chemical, known and training through whatever means are found N2O. Scavenging especially when acute and chronic health effects and related health appropriate and protective. Although there system vacuum interconnected information, primary route(s) of entry, exposure would always have to be some training on-site pump must with other dental limits, precautionary measures, emergency and (such as informing employees of the location have capacity scavenging first-aid procedures, and the identification of the and availability of the written program and to scavenge 45 systems. If organization responsible for preparing the sheet. MSDSs), employee training may be satisfied in lpm per dental undersized, As a source of detailed information on hazards, part by general training about the requirements operation. replace pump. copies of the MSDS for each hazardous chemical of the hazard communication standard and about must be readily accessible during each work shift chemical hazards on the job which is provided by, 5 Place mask on Secure mask with to employees when they are in their work area(s). for example, professional associations, colleges, patient and assure a “slip” ring for universities, and training centers. In addition, good, comfortable “good activity” Employers must prepare a list of all hazardous fit. Make sure from patient chemicals in the workplace, and the list should be previous training, education and experience of a worker may relieve the employer of some of the reservoir bag is not breathing. checked to verify that MSDSs have been received over- or under- for each chemical. If there are hazardous chemicals burdens of informing and training that worker. The employer, however, maintains the responsibility to inflated while the used for which no MSDS has been received, the patient is breathing. employer must contact the supplier, manufacturer ensure that employees are adequately trained and 6 Check general If smoke from or importer to obtain the missing MSDS. are equipped with the knowledge and information to do their jobs safely. ventilation for smoke tubes Health care employers must establish a training good room air indicate room air and information program for all personnel who are Step-by-step approach for controlling N2O mixing. Exhaust mixing is poor, involved in the handling of, or who have potential Step Procedure Control vents should not be then increase exposure to, anesthetic gases and other hazardous close to air supply the airflow or 1 Visually inspect Replace defective chemicals to apprise them of the hazards vents (use smoke redesign. If all N O equipment equipment and/or associated with these chemicals in the workplace. 2 tubes to observe exhaust vents (reservoir bag, parts. Training relative to anesthetic gases should place air movement in are close to air hoses, mask, an emphasis on reproductive risks. Training room.) supply vents, connectors) for and information must take place at the time of relocate (check worn parts, cracks, initial assignment and whenever a new hazard with ventilation holes, or tears. is introduced into the work area. At a minimum, engineers to make employees must be informed of the following: 2 Turn on the N2O Determine leak adjustments). ■■ The Hazard Communication Standard (29 tank and check source and fix. If 7 Conduct personal If personal CFR 1910.1200) and its requirements. all high- to tank valve leaks, sampling of dentist exposures exceed ■■ Any operations and equipment in the work low-pressure replace tank; if and dental assistant 150 ppm during area where anesthetic agents and hazardous connections for O-rings, gaskets, for N O exposure. administration, chemicals are present. leaks. Use a valves, hoses, or 2 Use diffusive improve mask fit ■■ Location and availability of the written non-oil-based fittings, replace. sampler or infrared and make sure it hazard communication program including the soap solution to Contact the gas analyzer (see is secure over the required lists of hazardous chemicals and the check for bubbles manufacturer for sampling methods). patient’s nose. required MSDS forms. at high pressure parts replacement. Minimize patient connectors, or use For threaded The employee training program must consist of talking while N O a portable infrared pipe fittings, use 2 the following elements: is administered. gas analyzer. Teflon tape. Do ■■ How the hazard communication program is not use this tape implemented in the workplace, how to read on compression and interpret information on the MSDS and fittings. label of each hazardous chemical, and how employees can obtain and use the available hazard information. ■■ The physical and health hazards of the chemicals in the work area. ■■ Measures employees can take to protect themselves from these hazards, including specific procedures put into effect by the employer

Page 28 Elite 8 Repeat procedure If personal in step 7. exposures are less nitrous oxide – N2O than 150 ppm but Final Examination Questions greater than 25 Choose True or False for questions 11-15 ppm, implement and mark your answers on the Final auxiliary exhaust Examination sheet found on page 97 or ventilation near complete your test online at the patient’s www.onlinedentalCE.com. mouth. Capture distance should 11. Long-term exposure to nitrous oxide can no greater than 10 cause reproductive side effects. inches from the True False patient’s nose and mouth area and exhaust no less 12. The National Institute for Occupational than 250 cfm at Safety and Health recommended, in the hood opening. a technical report published in 1977, Avoid getting controlling exposure limits of nitrous oxide between the waste to 35 parts per million (ppm) of air auxiliary exhaust during dental surgery. hood and patient’s True False mouth and nose area. 13. Inhaled anesthetic agents include two Conclusion different classes of chemicals. Nitrous oxide is used in many dental and medical True False offices and should be used with care. It is the most frequently used sedation method used in 14. Venting waste anesthetic gas via the dentistry. All bodily functions remain normal, exhaust grille or exhaust duct of a non- and the patient is able to breathe on his/her recirculating ventilation system is an own. The patient will not fall asleep and will example of an active system. not have memory loss. It is best used for mildly anxious patients who wish only a small amount True False of sedation to “take the edge off” or to make them less nervous. The patient is able to respond 15. Three fundamental types of air samples can appropriately to physical stimulation and verbal be taken to evaluate the workplace; they commands. It is a way for the dentist to manage are personal, area and source samples. pain and anxiety during dental appointments, but they must also administer it wisely and with True False caution. Each dental or medical office should establish its own comprehensive training program on how to maintain the equipment and proper safety standards. This course should help you to review your office routines and make sure you are setting the way to achieve the best safety standards for your patients and for your employees.

Bibliography “Nitrous oxide and its abuse”; Theodore J. Jastak, Journal of the American Dental Association, 1991. Abstract accessed Sept. 15, 2010, at http://www.faqs.org/abstracts/Health/Nitrous- oxide-and-its-abuse-Quantification-and-analysis-of-pain-in- nonsurgical-scaling-and-or-root-p.html. “46 Health Care Professionals Linked to Substance Abuse,” Bristol Herald Courier, April 26, 2009. Federation of State Physician Health Programs. http://www. fsphp.org. Nitrous Oxide-Oxygen: A New Look at a Very Old Technique; Stanley F. Malamed, DDS, and Morris S. Clark, DDS. Journal of the California Dental Association. 2003

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Elite Page 29 Figure 5 nitrous oxide – N2O Figures 1 through 7 in chapter Figure 1

Figure 6

Figure 2

Figure 3

Figure 7

Figure 4

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