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Abstract
BACKGROUND Nitrous oxide (N2O) is a frequently used anaesthetic. Since the year 2000, recreational use of N2O, also known as 'laughing gas', became popular as a recreational drug due to its mild psychedelic effect. In the 1980s, several reports warned against N2O-induced reproductive risks among healthcare personnel, questioning the occupational safety of N2O in health care. METHODS Data about the reproductive risks of N2O were collected from literature. RESULTS Particularly in the past, professionals working in dental and midwifery practices, operating theatres and ambulance transport were exposed to high levels of N2O. Adverse reproduction effects included congenital anomalies, spontaneous abortion and reduced fertility rates in females. Following occupational measures, like maximal exposure limits for ambient N2O, this occupational risk was considerably reduced. Recreational users of N2O, however, voluntarily and repeatedly expose themselves to (very) high doses of N2O. As such, they exceed the health exposure limits some hundred times, but they are fully unaware of the related reproductive risks. CONCLUSION We advocate to increase the awareness in recreational N2O-users about its potential reproductive risks, especially in heavy users, pregnant users or those who intend to become pregnant.
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Affiliation(s)
- Jan van Amsterdam
- Jan van Amsterdam, Department of
Psychiatry, Academic Medical Center, University of Amsterdam, P.O. Box
22660, 1100 DD Amsterdam, The Netherlands. Emails:
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Menon JML, van Luijk JAKR, Swinkels J, Lukas E, Ritskes-Hoitinga M, Roeleveld N, Schlünssen V, Mandrioli D, Hoffmann S, Popa M, Scheepers PTJ. A health-based recommended occupational exposure limit for nitrous oxide using experimental animal data based on a systematic review and dose-response analysis. ENVIRONMENTAL RESEARCH 2021; 201:111575. [PMID: 34174259 DOI: 10.1016/j.envres.2021.111575] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Revised: 06/18/2021] [Accepted: 06/20/2021] [Indexed: 06/13/2023]
Abstract
BACKGROUND Nitrous oxide (N2O) is a common inhalation anaesthetic used in medical, paramedical, and veterinary practice. Since the mid 1950's, concerns have been raised regarding occupational exposure to N2O, leading to many epidemiological and experimental animal studies. Previous evaluations resulted in the classification of N2O as a possible risk factor for adverse reproductive health outcomes based on animal data. Human data were deemed inadequate primarily because of simultaneous co-exposures to other risk factors for adverse reproductive and developmental outcomes, including other anaesthetic gases. Since previous evaluations, controversies regarding N2O use remained and new approaches for dose response modelling have been adopted, calling for an update and re-evaluation of the body of evidence. This review aims to assess available animal evidence on N2O reproductive and developmental outcomes to inform a health-based recommended occupational exposure limit (OEL) for N2O with a benchmark dose-response modelling (BMD) approach. METHODS Comprehensive searches in PubMed, EMBASE, and Web of Science were performed to retrieve all relevant studies addressing reproductive and developmental outcomes related to inhalation of N2O in animals. The articles retrieved were screened based on title-abstract and full text by two independent reviewers. After data extraction, an overview of all studies was created for the different endpoints, namely foetal outcomes (e.g., resorption), female outcomes (e.g. implantations), and male outcomes (e.g. sperm count). A subset of studies reporting on exposure relevant to workplace settings and with a sufficient number of tested doses were included in dose-response modelling using the BMD approach. RESULTS In total, 15.816 articles were retrieved, of which 47 articles were finally included while 4 of those were used for the quantitative data synthesis. The overall risk of bias was judged to be probably high (using OHAT risk of bias tool) and unclear (using SYRCLE's risk of bias tool). From eligible rat studies, three studies provided an acceptable result by fitting a Hill model to the dose-response data. The resulting benchmark dose lower bounds (BMDLs) from three studies converged to an average (±sd) exposure level of 925 ± 2 mg/m3 at an additional risk of one standard deviation of implantation losses above those observed in the control group (i.e. reduced number of live foetuses/mother). For extrapolation from rats to humans, an uncertainty factor of 10 was used and an additional factor of 5 was applied to account for interindividual variability within the population of workers. CONCLUSION With this systematic review, all available evidence for reproductive toxicity and adverse developmental outcomes in animals resulting from inhalation exposure to N2O was used to derive a health-based OEL recommendation of 20 mg/m3 as 8-h time-weighted average.
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Affiliation(s)
- Julia M L Menon
- Department for Health Evidence, Radboud Institute for Health Sciences, Radboudumc, Nijmegen, the Netherlands
| | - Judith A K R van Luijk
- Department for Health Evidence, Radboud Institute for Health Sciences, Radboudumc, Nijmegen, the Netherlands
| | - Janne Swinkels
- Department for Health Evidence, Radboud Institute for Health Sciences, Radboudumc, Nijmegen, the Netherlands
| | - Eva Lukas
- Faculty of Science, Radboud University, Nijmegen, the Netherlands
| | - Merel Ritskes-Hoitinga
- Department for Health Evidence, Radboud Institute for Health Sciences, Radboudumc, Nijmegen, the Netherlands; Department of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Nel Roeleveld
- Department for Health Evidence, Radboud Institute for Health Sciences, Radboudumc, Nijmegen, the Netherlands
| | - Vivi Schlünssen
- Department of Public Health, Danish Ramazzini Centre, Aarhus University, Aarhus, Denmark and National Research Center for the Working Environment, Copenhagen, Denmark
| | - Daniele Mandrioli
- Cesare Maltoni Cancer Research Center, Ramazzini Institute, Bologna, Italy
| | - Sebastian Hoffmann
- The Evidence-Based Toxicology Collaboration (EBTC), Johns Hopkins Bloomberg School of Public Health, Baltimore, USA
| | | | - Paul T J Scheepers
- Department for Health Evidence, Radboud Institute for Health Sciences, Radboudumc, Nijmegen, the Netherlands.
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Ding Y, Yu J, Qu P, Ma P, Yu Z. The negative effects of chronic exposure to isoflurane on spermatogenesis via breaking the hypothalamus-pituitary-gonadal equilibrium. Inhal Toxicol 2015; 27:621-8. [DOI: 10.3109/08958378.2015.1080772] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Ceyhan A, Cincik M, Bedir S, Ustun H, Dagli G, Kalender H. EFFECTS OF EXPOSURE TO NEW INHALATIONAL ANESTHETICS ON SPERMATOGENESIS AND SPERM MORPHOLOGY IN RABBITS. ACTA ACUST UNITED AC 2009; 51:305-15. [PMID: 16036639 DOI: 10.1080/0148501090919675] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The effects of chronic exposure to new inhalation anesthetics (sevoflurane and isoflurane) on spermatogenesis and sperm morphology were examined in 23 rabbits, randomly divided in 3 groups. Rabbits received 20 exposure hours (four hours/day x 5 days), as follows: group I: 2.3% (1.2 MAC) sevoflurane + 2L/min oxygen, group II: 1.3% (1.2 MAC) isoflurane + 2L/min oxygen, and group III (control): 2L/min oxygen. Semen was collected on the 12th, 19th, 26th, 33rd, and 41st days of exposure. Sperm concentration, motility and morphological changes were evaluated. On the 41st day, testicular biopsies were taken and observed with light microscopy. Sperm concentration and motility significantly decreased in the sevoflurane and the isoflurane groups, compared to control. There were no significant changes in the control group. It is concluded that chronic exposure to the new inhalational anesthetics had negative effects on spermatogenesis and sperm morphology.
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Affiliation(s)
- A Ceyhan
- Ministry of Health Ankara Training and Research Hospital, Department of 1st Anesthesiology Clinic, Ankara, Turkey
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Yamada K, Kawata T, Wada M, Mori K, Tamai H, Tanaka N, Tadokoro T, Tobimatsu T, Toraya T, Maekawa A. Testicular Injury to Rats Fed on Soybean Protein-Based Vitamin B12-Deficient Diet Can Be Reduced by Methionine Supplementation. J Nutr Sci Vitaminol (Tokyo) 2007; 53:95-101. [PMID: 17615995 DOI: 10.3177/jnsv.53.95] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
We have previously reported that rats fed on a vitamin B12 (B12)-deficient diet containing 180 g soybean protein per kg diet showed marked histologic damage in their testes. In this paper, we report the effect of B12-deficiency on B12-dependent methionine synthase in the rats' testes and the effect of methionine supplementation of the diet on testicular damage. Rats were fed the soybean protein-based B12-deficient diet for 120 d. We confirmed that those rats were in serious B12-deficiency by measuring urinary methylmalonic acid excretion and B12 content in tissues. Methionine synthase activity in the testis of the B12-deficient rats was less than 2% of that in B12-supplemented (control) rats. To complement disrupted methionine biosynthesis, methionine was supplied in the diet. A supplement of 5 g D,L-methionine per kg diet to the B12-deficient diet did not affect urinary methylmalonic acid excretion of B12-deficient rats. The testicular histology of rats fed the methionine-supplemented B12-deficient diet was almost indistinguishable from that of control rats. Thus, we conclude that the lowered testicular methionine synthase activity is the primary cause of the histologic damage due to B12-deficiency and that methionine supplementation to the diet can reduce the damage. These findings would indicate the importance of the methionine synthase activity, especially for testicular function.
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Affiliation(s)
- Kazuhiro Yamada
- Faculty of Engineering, Okayama University, Okayama 700-8530, Japan
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Badgwell JM. An evaluation of air safety source-control technology for the post anesthesia care unit. J Perianesth Nurs 1996; 11:207-22. [PMID: 8964013 DOI: 10.1016/s1089-9472(96)80020-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A new source-control system designed specifically to address the most important air safety hazards in the post anesthesia care unit (PACU) is presented--the transmission of bloodborne and respiratory pathogens, and occupational exposure to waste anesthetic gases. The controversy arising from research in the 1970s, 1980s, and 1990s regarding waste anesthetic gases, government regulations that responded to air safety hazards, and the resulting de facto use of scavenging systems in almost all operating rooms across the United States is discussed. However, a similar concern does not apply to the PACU although its unique characteristics make it an especially high-risk environment for air safety hazards.
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Abstract
The etiology of male infertilities is largely undetermined, and our knowledge of exogenous factors affecting the male reproductive system is still limited. In particular, the role of specific environmental and occupational factors is incompletely elucidated. Various occupational (physical and chemical) agents have been shown to affect male reproductive functions in animals, but large differences in reproductive function and/or xenobiotic handling between species limit extrapolation to humans. When available, human data are often conflicting and, except in a few instances, usually refer to broad and heterogenous occupational categories or to groups of agents (e.g., solvents). It is often difficult to elucidate the role of a single agent because occupational exposure conditions are often complex and various confounding factors related to lifestyle (smoking, alcohol, and diet) or socioeconomic state may also affect sperm quality, fertility, or pregnancy outcomes. The objective of this work is to summarize the main epidemiological and, where relevant, experimental findings pertaining to agents (physical and chemical) encountered in the occupational environment that might affect the male reproductive system (sperm count, motility and morphology, libido, and fertility) and/or related pregnancy outcomes (spontaneous abortion, stillbirth, low birth weight, and birth defects and childhood malignancy in offspring). Some methodological issues related to research on the reproductive effects of toxicants are also discussed briefly.
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Affiliation(s)
- S Tas
- Industrial Toxicology and Occupational Medicine Unit, School of Medicine, Catholic University of Louvain, Brussels, Belgium
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Holson RR, Bates HK, LaBorde JB, Hansen DK. Behavioral teratology and dominant lethal evaluation of nitrous oxide exposure in rats. Neurotoxicol Teratol 1995; 17:583-92. [PMID: 8552005 DOI: 10.1016/0892-0362(95)00019-n] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Epidemiological studies have suggested that spontaneous abortion may be increased in medical personnel following the sort of chronic low-level exposure to the anesthetic gas nitrous oxide (N2O) seen in surgical or dental operatories. These results are supported by some, but not all, animal studies, and results are less well established at low exposure levels. Behavioral effects in exposed animal offspring have also been observed, but again not in all studies. To further examine this problem, we conducted the present experiments. Adult male or female rats were exposed to trace concentrations of N2O (0%, 0.1%, 0.5%, or 1.0% in air) for 6 h daily either throughout gestation (females) or for 9 weeks (males). Offspring from treated adults were subjected to an extensive behavioral test battery. There were no clear dose-response effects on any of eight behavioural tests for any offspring. Maternal and offspring weights were normal from conception through adulthood. Additionally, we studied effects of N2O on male fertility by mating treated males with untreated females and examining uterine contents. There was no evidence for a substantial decline in fertility of exposed males, although there was a small dose-related trend for resorptions to increase and live births to decrease with increasing paternal N2O exposure. There results suggest that there is little alteration in male or female fertility following chronic exposure to low levels of N2O. There are also no significant long-term behavioral alterations in offspring exposed gestationally to trace levels of N2O via dam or sire.
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Affiliation(s)
- R R Holson
- Division of Reproductive and Developmental Toxicology, National Center for Toxicological Research, Jefferson, AR 72079, USA
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Toxicity of inhalational anaesthesia: long-term exposure of anaesthetic personnel—environmental pollution. ACTA ACUST UNITED AC 1993. [DOI: 10.1016/s0950-3501(05)80155-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Andersen BN, Mortensen JT, Hansen P, Jakobsen J, Johansen JP. The influence of halothane on spermatogenesis in surgical patients. Acta Anaesthesiol Scand 1992; 36:125-7. [PMID: 1549930 DOI: 10.1111/j.1399-6576.1992.tb03437.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Seventeen male patients delivered a sperm sample before and 80-90 days after halothane anaesthesia, acting as their own control. The sample was tested according to WHO criteria. There was no difference before and after anaesthesia. We conclude that halothane used in normal anaesthetic concentration in combination with nitrous oxide during arthroscopic knee surgery had no certain effect on the quality of sperm.
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Affiliation(s)
- B N Andersen
- Department of Anesthesiology, Aalborg Hospital, Denmark
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McDiarmid MA, Lees PS, Agnew J, Midzenski M, Duffy R. Reproductive hazards of fire fighting. II. Chemical hazards. Am J Ind Med 1991; 19:447-72. [PMID: 2035546 DOI: 10.1002/ajim.4700190404] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Studies of the health of fire fighters have historically focused on non-malignant respiratory disease and cancer. More recently, concerns have surfaced about reproductive health effects in many areas of the workforce, including fire fighting. These concerns prompted this review of chemical exposures that may contribute to adverse reproductive health outcomes in male as well as female fire fighters. A review of the industrial hygiene literature was undertaken to identify agents commonly found in fire smoke. These agents were then examined for evidence of reproductive toxicity or mutagenicity/carcinogenicity. This profile of chemical agents and their reproductive toxicities permits a qualitative determination that fire fighters are exposed to potential reproductive toxicants as a part of their normal fire fighting duties. Considerations for mitigating these risks are also discussed.
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Affiliation(s)
- M A McDiarmid
- Department of Environmental Health Sciences, School of Hygiene and Public Health, The Johns Hopkins University, Baltimore, MD 21205
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Ladrón de Guevara O, Adaya Godoy A, Cortinas de Nava C. Quantification of halothane, enflurane and nitrous oxide by means of a simple gas chromatographic method. J Chromatogr A 1987; 403:350-4. [PMID: 3680422 DOI: 10.1016/s0021-9673(00)96375-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Affiliation(s)
- O Ladrón de Guevara
- Departamento de Biologia del Desarrollo, Universidad Nacional Autónoma de México, D.F
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Barr FM. Waste anaesthetic gas exposure in veterinary surgeries: a need for scavenging systems. N Z Vet J 1987; 35:68-71. [PMID: 16031379 DOI: 10.1080/00480169.1987.35386] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- F M Barr
- Faculty of Veterinary Science, Massey University, Palmerston North
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Abstract
Although once considered completely devoid of complications, it is now recognised that the misuse or inappropriate use of nitrous oxide (N2O) often results in adverse side effects. Hypoxia, particularly the entity 'diffusion hypoxia', can occur with the administration of inadequate amounts of oxygen during or immediately after a N2O anaesthetic. N2O will diffuse into air-containing cavities within the body faster than nitrogen diffuses out. This results in a temporary increase in either the pressure and/or volume of the cavity depending upon the distensibility of its walls. The magnitude of the effect is proportional to the blood supply of the cavity, the concentration of N2O inhaled and the length of time the patient is exposed to N2O. Significant morbidity or even death can result from this phenomenon. A property unique to N2O is its ability to oxidise and inactivate the vitamin B12 components of certain enzymes in both animals and man. One such enzyme, methionine synthetase is essential for normal DNA production. Animal and human studies have demonstrated that the haematological, immune, neurological and reproductive systems are each affected. These adverse effects of N2O can occur after both acute (surgical) or long term (occupational) exposure to the gas. Because of its effects on the pressure and volume characteristics of air-containing spaces, N2O should not be used for patients with bowel obstruction, pneumothorax, middle ear and sinus disease, and following cerebral air-contrast studies. Many anaesthesiologists feel that use of N2O should be restricted during the first two trimesters of pregnancy because of its effects on DNA production and the experimental and epidemiological evidence that N2O causes undesirable reproductive outcomes. Since N2O affects white blood cell production and function, it has been recommended that N2O not be administered to immunosuppressed patients or to patients requiring multiple general anaesthetics. Many anaesthesiologists believe that the potential dangers of N2O are so great that it should no longer be used at all for routine clinical anaesthesia. However, the continued use of N2O remains a controversial topic since, at present, a suitable substitute gas is not available.
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Mazze RI, Rice SA, Wyrobek AJ, Felton JS, Brodsky JB, Baden JM. Germ cell studies in mice after prolonged exposure to nitrous oxide. Toxicol Appl Pharmacol 1983; 67:370-5. [PMID: 6845366 DOI: 10.1016/0041-008x(83)90320-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Male and female Swiss Webster (SW) mice, age 13 to 14 weeks, were exposed by inhalation for 4 hr per day, 5 days per week, for 14 weeks, to either room air, 0.5% nitrous oxide, 5.0% nitrous oxide, or 50% nitrous oxide. Murine germ cells were examined for evidence of injury after this exposure. A group of male mice were treated with methyl methanesulfonate (MMS) as a positive control for sperm abnormalities while a group of female mice were treated with 3-methylcholanthrene (3-MC) as a positive control for oocyte destruction. There were no significant differences among the four inhalation exposure groups in testes weight, percentage of abnormally shaped sperm, sperm count, or histologic appearance of the testes; the mean percentage (+/- SE) of abnormal sperm ranged from 8.9 +/- 2.4 (5.0% nitrous oxide) to 13.5 +/- 0.5 (50% nitrous oxide) with a concurrent control value of 10.4 +/- 2.3%. In the positive control experiment, 25.2 +/- 4.1% of sperm from mice treated with MMS were abnormal compared with 2.5 +/- 0.3% of sperm from mice treated with saline (p less than 0.001), indicating that sperm of SW mice are sensitive to chemical damage. There was no significant difference between the mean number of oocytes in mice treated with 50% nitrous oxide (33.3 +/- 14.4) and in control mice (29.8 +/- 8.0). In the positive control experiment, mice treated with 3-MC had significantly fewer (p less than 0.001) primordial oocytes, 67.2 +/- 19.5 compared with control mice, 222.4 +/- 21.9, indicating that this strain is sensitive to chemical damage of the ovary. Thus, murine germ cells showed no evidence of toxic effects due to prolonged exposure to nitrous oxide.
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Rupreht J, Dzoljic MR. Elimination of irritating compounds during chronic exposure to gases. JOURNAL OF PHARMACOLOGICAL METHODS 1982; 8:109-14. [PMID: 6815382 DOI: 10.1016/0160-5402(82)90064-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Ammonia (NH3, a degradation product of urine) and intestinal gases which accumulate in the experimental circuit during the long-term experimental exposure of rats to gases might cause disturbing irritation in the behavior of the animals. A relatively simple and cheap experimental arrangement has been suggested for the elimination of these irritating compounds. This system also guarantees the maintenance of a constant concentration of the investigated gases. In order to facilitate the comparison of the results of various studies, the standardization of the basic experimental procedure for the long-term exposure to gases has been suggested.
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Abstract
The anaesthetic gas nitrous oxide (N2O), when inhaled for longer than 6 hr, produces megaloblastic anemia in man. Longer term inhalation, as in addicts, produces a syndrome similar to that due to B12 neuropathy, and long term exposure to low concentrations results in an increased abortion rate and neuropathy, particularly in dental personnel. N2O acts by oxidizing vitamin B12 from the active reduced cob[I]alamin form to the inactive cob[III]alamin form. In turn, this inactivates the enzyme methionine synthetase which requires both B12 and folate as cofactors. In the rat, hepatic methionine synthetase is completely inactivated after 3 hr exposure to a mixture of equal parts of N2O/O2. There is an impared uptake of folate analogues by the liver so that the plasma folate level rises and thereafter there is a considerable loss of folate into the urine. Hepatic folate concentration falls to 25% within 10 days of N2O exposure. There is a failure to synthesize folate polyglutamate (the active folate coenzyme) from all other than formyltetrahydrofolate. As oxidization of the methyl of methionine is an important source of formyl, the failure of methionine synthesis in turn appears to lead to the failure in supply of formate and, hence, a lack of the formylfolate substrate.
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Abstract
Nitrous oxide (N2O) is marketed as an inhalation anesthetic and as a food ingredient (e.g., whipping cream propellant). In the human, inhalation has been associated with "highs," peripheral nerve damage, mitotic poisoning of bone marrow, psychosis, and mental impairment. Exposure to hypoxemic mixtures has resulted in death. The commercial N2O sources specifically studied were aerosol whipping cream containers (three brands) and 6.5-cm cylinders, or chargers (two brands). The gas content and N2O concentrations of these devices were measured. The aerosol cans, when not shaken, will dispense at least 3 liters of 87 to 90% N2O. Charger misuse may occur when they are substituted for identically designed carbon dioxide (CO2) chargers of a seltzer bottle; 4.3 to 5.0 liters of 93 to 98% N2O is expelled at a controllable rate. The toxicity of these inexpensive N2O products, their high potential for misuse, and the absence of labeling (chargers) argue that their distribution be discontinued.
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Abstract
A neurological disorder developed after prolonged exposure to nitrous oxide in 15 patients, all but 1 of whom were dentists. 13 patients had abused nitrous oxide to some extent for periods ranging from 3 months to several years, but 2 patients were exposed to nitrous oxide only professionally, by working in poorly ventilated surgeries. Symptoms included early sensory complaints, Lhermitte sign, loss of balance, leg weakness, gait ataxia, impotence, and sphincter disturbances. Neurological examination showed sensorimotor polyneuropathy, often combined with signs of involvement of the posterior and lateral columns of the spinal cord. Electrodiagnostic tests pointed to an axonal polyneuropathy, but other laboratory results were normal, including examination of the spinal fluid. The neurological picture is similar to that of subacute combined degeneration of the spinal cord, and it is possible that nitrous oxide interferes with the action of vitamin B12 in the nervous system.
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Whitcher CE, Zimmerman DC, Tonn EM, Piziali RL. Control of occupational exposure to nitrous oxide in the dental operatory. J Am Dent Assoc 1977; 95:763-76. [PMID: 143480 DOI: 10.14219/jada.archive.1977.0493] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Methods were developed for controlling the dental team's occupational exposure to nitrous oxide. The most applicable and effective use of these methods included the use of properly maintained gas delivery equipment, a double-walled scavenging nosepiece and vented suction machine, and minimizing speech by the patients. These methods were evaluated by measuring concentrations of nitrous oxide present in the air inspired by dental personnel. Before their use, the dentist inhaled 900 ppm nitrous oxide; their application reduced his inhaled concentration to 31 ppm, representing a 97% reduction. These methods were well accepted during 157 procedures completed by a group of eight dentists engaged in private practice (four general practitioners, two pedodontists, and two oral surgeons).
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Abstract
Data have been reviewed relevant to the effects of chronic exposure to trace quantities of inhalation anesthetic agents. Much circumstantial evidence exists indicating a probable hazard to the clinician administering these agents. However, all previous studies in man have not identified the potential hazard of nitrous oxide without the presence of other contaminating agents.
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Jones TW, Greenfield W. Position paper of the ADA Ad Hoc Committee on trace anesthetics as a potential health hazard in dentistry. J Am Dent Assoc 1977; 95:751-6. [PMID: 269186 DOI: 10.14219/jada.archive.1977.0484] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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