Some science behind the scenes
Nitrous Oxide
Nitrous oxide, commonly known as laughing gas, is a chemical compound with the formula N2O. The gas was first synthesized by English chemist Joseph Priestley in 1772, who called it phlogisticated nitrous air or ‘phlogiston’. Priestley published his discovery in the book Experiments and Observations on Different Kinds of Air (1775).
At room temperature, it is a colourless, non-flammable gas, with a slightly sweet odour and taste. It is used in surgery and dentistry for its anaesthetic and analgesic effects. It is a relatively potent analgesic but a weak anaesthetic and has been in use since 1842. The 180 plus years of its use have tended to identify most of its complications. One of the biggest problems for an anaesthetist is that it has an ability to diffuse into and then expand any air filled cavities, but it does have other serious side effects.
One perhaps key aspect about Nitrous oxide is that it is, like Xenon, a naturally occurring gas – it is not man made. Nitrous oxide is emitted by bacteria in soils and oceans, and thus has been a part of Earth's atmosphere for millennia. Human activity is thought to account for about 30% of nitrous oxide release whereas tropical soils and oceanic release account for 70%. To put this another way it is non toxic at normal levels of exposure and the body can cope with slightly higher exposure temporarily.
Agriculture is the main source of human-produced nitrous oxide: cultivating soil, the use of nitrogen fertilizers, and animal waste handling can all stimulate naturally occurring bacteria to produce more nitrous oxide. The livestock sector (primarily cows, chickens, and pigs) produces 65% of human-related nitrous oxide. Industrial sources make up only about 20% of all anthropogenic sources, and include the production of nylon, and the burning of fossil fuel in internal combustion engines.
Nitrous oxide gives rise to NO (nitric oxide) on reaction with oxygen atoms, and this NO in turn reacts with ozone. As a result, it is the main naturally occurring regulator of stratospheric ozone. It is also a major greenhouse gas and air pollutant. Considered over a 100-year period, it has 298 times more impact 'per unit weight' (Global warming potential) than carbon dioxide. Thus, despite its low concentration, nitrous oxide is the fourth largest contributor to these greenhouse gases. It ranks behind water vapor, carbon dioxide, and methane. Control of nitrous oxide is part of efforts to curb greenhouse gas emissions.
Effects
All the following effects have been obtained from Meyler’s side effects of drugs and the papers that follow this section. The one off effects of nitrous oxide are relatively manageable, but the longer term effects of exposure are more serious than was perhaps originally envisaged.
- Cardiovascular and respiratory depression – is the main side effect of nitrous oxide, ‘which is otherwise well tolerated’. Because nitrous oxide can worsen myocardial ischemia in patients with heart problems ‘critical coronary stenosis’ the mixture of gases given during anaesthesia is very carefully monitored as is the patient
- Peripheral neuropathy and megaloblastic anaemia can occur after chronic exposure
- Malignant hyperthermia occurs but is rarely encountered
- Hypoxia during recovery occasionally occurs
- Trauma - Nitrous oxide diffuses into the endotracheal tube cuff and can overexpand it provoking upper airway obstruction, hypoxemia [deficiency of oxygen in arterial blood] and trauma
- Myelineuropathy – this condition is serious but is noticeable only in people who have had regular or frequent exposure to nitrous oxide. These include dentists and dental nurses, not just so called ‘recreational users’. Disorders that concomitantly affect the spinal cord and peripheral nerves are called myeloneuropathies. These disorders may present with predominantly myelopathic or peripheral neuropathic signs and symptoms, and as it says in the book “a careful neurologic examination and a thoughtful diagnostic evaluation are necessary to establish a diagnosis”. People get numbness in the hands or legs, an unsteady gait, impotence, ‘sphincter disturbances’, muscle weakness, more details can be found in the background papers
- Female Infertility - women exposed to high levels of nitrous oxide were significantly less fertile than women who were unexposed or exposed to lower levels of nitrous oxide.
- Spontaneous abortion - exposure to high levels of nitrous oxide increases the risk of spontaneous abortion. The interaction with vitamin B12 causes changes in DNA synthesis ‘that could be important in the first trimester of pregnancy”. The vitamin B12 deficiency associated with prolonged use of N2O increases the risk of bearing a child with an open spinal cord or an undeveloped brain
- Male infertility - normal vitamin B12 activity appears to be essential for both male and female fertility. Lower-than-normal levels of vitamin B12 are seen in the semen of men with a high percentage of morphologically abnormal sperm. Testicular methionine synthase activity is depressed by higher, clinically relevant concentrations of nitrous oxide
- Megaloblastic marrow changes and numerous other effects on the spinal cord “ the use of nitrous oxide in bone marrow transplantation needs to be evaluated and cannot be recommended”
- Kidney function disturbances have been described
- Tympanic rupture – nitrous oxide increases middle ear pressure and spontaneous tympanic rupture has been described
- ‘Recreational’ use danger - While nitrous oxide is not a dangerous substance per se, ‘recreational users’ typically find it quite difficult to find a way of mixing it with air or oxygen. In the medical context, a dentist, for example, will provide a 70/30 mix of nitrous oxide and oxygen, respectively, in order to produce a dose which eliminates pain but retains consciousness. A spiritual explorer is going to be hard pressed to recreate this precise mix or a mix with more nitrous oxide and less air in order to increase the effect. There is a real risk in these circumstances that you could die from lack of oxygen - hypoxia.
- PO2 readings - Nitrous oxide inhalation can give false PO2 readings – a reading which is used to measure the amount of oxygen in the blood. If you have any hospital visits for blood testing, it could give the wrong readings if you have been exposed to the gas
- Permanent memory loss - Excessive use could [and has ] cause permanent memory loss
- Delayed action - An inactive person who has breathed high concentrations for 20-30 minutes but then breathes normally will still retain the gas in his body at low doses as the gas slowly migrates back out of these internal cavities. Even after several hours of not breathing the gas, sudden rapid whole-body movements will cause the dissolved gas to suddenly begin migrating out of fat cells, resulting in a latent dosing effect. This is inherently dangerous in that a person at the dentists or a party, for example, can think the effects are over, attempt to drive home and ….. crash
- Innocent victims - Because nitrous oxide is minimally metabolised, it retains its potency when exhaled into the room. In a medical environment it can pose an intoxicating and prolonged-exposure hazard to the clinic staff if the room is poorly ventilated, and it may equally well pose a hazard to the helper of any so called recreational user who could get as high as the person using it unless the room is ventilated.
- Impurities cause death – nitrous oxide has to be produced by large scale chemical processes and stored in safe, tamper proof bottles with proper inhalers. Thus pure nitrous oxide is not readily available or cheap. Smaller bottles of nitrous oxide without the inhalers are available for approved use as a food additive, and it is possible to get hold of these as a cheaper more practical source, but administration then becomes more difficult and more risky. Some of the even smaller containers contain a mixture of gases and are thus not safe. They have caused deaths
Background papers
Clin Toxicol (Phila). 2008 Dec;46(10):1095-6. doi: 10.1080/15563650802356617.
Myeloneuropathy in a dentist - Meyers LE, Judge B
Grand Rapids MERC/Michigan State University Program in Emergency Medicine, Grand Rapids, MI, USA.
We present a case of a 49-year-old male dentist with myeloneuropathy. He used nitrous oxide frequently in his practice, and denied recreational use. Magnetic resonance imaging (MRI) of his cervical and thoracic spinal cord demonstrated a hyperintense signal on T2 within the posterior columns. The patient was treated with vitamin B12 and l-methionine. A repeat MRI of his cervical spinal cord 3 months after hospital discharge showed complete regression of the hyperintense signal on T2 within the posterior columns.
PMID: 18763150
Severe myeloneuropathy from acute high-dose nitrous oxide (N2O) abuse.
Alt RS Morrissey RP, Gang MA Hoffman RS, Schaumburg HH.
Department of Emergency Medicine, New York University/Bellevue Hospital Center, New York, New York 10016, USA.
BACKGROUND:
Myeloneuropathy from chronic exposure to nitrous oxide has been described. Nitrous oxide irreversibly alters B(12) activation, causing signs and symptoms of B(12) deficiency.
OBJECTIVES:
We describe a case of myeloneuropathy secondary to acute use of high-dose nitrous oxide.
CASE REPORT:
A 24-year-old man presented to the Emergency Department complaining of numbness and tingling of his hands and feet, as well as worsening clumsiness and gait disturbances after escalating use of nitrous oxide in the prior 2 weeks. He was found to have dysmetria, poor proprioception, decreased sensation to vibration and light touch over his extremities, and a mildly positive Romberg sign. Laboratory test values revealed a normal B(12) level but increased methylmalonic acid and homocysteine levels. The patient was admitted to the hospital and started on a course of B(12) injections. He was discharged after 3 days with daily B(12) supplementation.
CONCLUSIONS:
This case demonstrates myeloneuropathic changes secondary to acute high-dose nitrous oxide exposure.
Copyright © 2011 Elsevier Inc. All rights reserved.
PMID: 20605391
Anesth Prog.1991 Jan-Feb;38(1):1-11. Health hazards and nitrous oxide: a time for reappraisal. Yagiela JA; Section of Oral Biology, School of Dentistry, University of California, Los Angeles.
Recent adoption by the American Conference of Governmental Industrial Hygienists of a Threshold Limit Value of 50 ppm for an 8-hour average exposure to nitrous oxide (N2O) increases the likelihood for its regulation by state and federal occupational health agencies. This review outlines current information on the health risks of N2O inhalation to provide a basis from which safe and reasonably attainable exposure limits can be proposed. Although N2O was for many years believed to have no toxicity other than that associated with its anesthetic action, bone marrow depression in patients administered N2O for extended periods of time and neurological abnormalities in health care workers who inhaled N2O recreationally have disproved this notion. Retrospective surveys of dental and medical personnel have also linked occupational exposure to N2O with a number of health problems and reproductive derangements. Nitrous oxide reacts with the reduced form of vitamin B12, thereby inhibiting the action of methionine synthase, an enzyme that indirectly supports methylation reactions and nucleic acid synthesis. Many, if not all, of the nonanesthetic-related adverse effects of N2O may be ascribed to this action. Animal and human studies indicate that the toxic effects of N2O are concentration- and time-dependent. It is suggested that a time-weighted average of 100 ppm for an 8-hour workday and/or a time-weighted average of 400 ppm per anesthetic administration would provide adequate protection of dental personnel and be achievable with existing pollution control methods.
PMID: 1809046
N Engl J Med. 1992 Oct 1;327(14):993-7 Reduced fertility among women employed as dental assistants exposed to high levels of nitrous oxide - Rowland AS, Baird DDWeinberg CRShore DL Shy CMWilcox AJ ; Epidemiology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
BACKGROUND:
Fertility is reduced in female rats exposed to levels of nitrous oxide similar to those found in some dental offices. Epidemiologic studies have suggested an association between exposure to mixed anesthetic gases and impaired fertility. We investigated the effects of occupational exposure to nitrous oxide on the fertility of female dental assistants.
METHODS:
Screening questionnaires were mailed to 7000 female dental assistants, ages 18 to 39, registered by the California Department of Consumer Affairs. Sixty-nine percent responded. Four hundred fifty-nine women were determined to be eligible, having become pregnant during the previous four years for reasons unrelated to the failure of birth control, and 91 percent of these women completed telephone interviews. Detailed information was collected on exposure to nitrous oxide and fertility (measured by the number of menstrual cycles without contraception that the women required to become pregnant).
RESULTS:
After controlling for covariates, we found that women exposed to high levels of nitrous oxide were significantly less fertile than women who were unexposed or exposed to lower levels of nitrous oxide. The effect was evident only in the 19 women with five or more hours of exposure per week. These women were only 41 percent (95 percent confidence interval, 23 to 74 percent; P less than 0.003) as likely as unexposed women to conceive during each menstrual cycle.
CONCLUSIONS:
Occupational exposure to high levels of nitrous oxide may adversely affect women's ability to become pregnant.
Andrew S. Rowland, Ph.D.
Donna Day Baird, Ph.D.
Clarice R. Weinberg, Ph.D.
National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709
Our data suggest that exposure to high levels of nitrous oxide increases the risk of spontaneous abortion. We chose not to comment on the incidence of spontaneous abortion in the 418 women in our study because there were only 30 spontaneous abortions. However, pregnancy data on the 4856 women who returned our mailed screening questionnaire also suggest an increased risk of spontaneous abortion. Preliminary analysis indicates that women exposed to unscavenged nitrous oxide for five or more hours per week had a threefold increase in the risk of spontaneous abortion (relative risk, 3.1; 95 percent confidence interval, 1.5 to 6.2; P<0.002) after adjustment for age, smoking status, and exposure to ethylene oxide.
Neurologic problems associated with chronic nitrous oxide abuse in a non-healthcare worker. Iwata K, O'Keefe GB, Karanas A. Department of Medicine, St. Luke's-Roosevelt Hospital Center, College of Physicians and Surgeons, Columbia University, New York, New York, USA.
Chronic exposure to nitrous oxide (N2O) is known to be associated with hematologic and neurologic abnormalities. When this syndrome occurs, it is generally seen in health care workers, especially dentists and anesthesiologists, who have access to nitrous oxide. Here, however, we report a case of a 55-year-old non-healthcare worker who presented with multiple neurological abnormalities. His serum vitamin B12 level was low but his Shilling test was normal. His neurologic symptoms improved after cessation of inhaling nitrous oxide and starting vitamin B12 therapy. Physicians should consider nitrous oxide abuse in non-healthcare workers presenting with neurologic symptom of unclear cause.
At the conclusion of her editorial (Oct. 1 issue)1 on the toxic effects of nitrous oxide on reproduction in women, Baird suggested that fertility in men may be impaired by occupational exposure to nitrous oxide. There is already some evidence to support this contention.
Epidemiologic studies of anesthesiologists and dentists in the 1960s reported that the unexposed wives of men who were occupationally exposed to waste anesthetic gases (nitrous oxide and the more potent halogenated anesthetics) had an increased incidence of spontaneous abortion. The single epidemiologic study that specifically examined reproductive outcome in men exposed only to nitrous oxide found a dose-related increase in the incidence of spontaneous abortion in their wives.
Although nitrous oxide was once considered innocuous, evidence began to be gathered in the early 1950s that it had potentially serious side effects. Subsequently, it was demonstrated that nitrous oxide inactivates the vitamin B12-dependent enzyme methionine synthase, an enzyme involved in normal cell division and DNA production. Although its specific role is unknown, normal vitamin B12 activity appears to be essential for both male and female fertility. For example, exogenous vitamin B12 improves sperm motility and enhances artificial insemination in animals Lower-than-normal levels of vitamin B12 are seen in the semen of men with a high percentage of morphologically abnormal sperm. It has even been suggested that all patients with unexplained sterility be screened for a vitamin B12 deficiency
The mechanism for the undesirable reproductive outcomes in men and women occupationally exposed to nitrous oxide may be the depression of some essential vitamin B12-dependent process in the germ cell, mature spermatozoa, or oocyte by nitrous oxide. Testicular methionine synthase activity is depressed by higher, clinically relevant concentrations of nitrous oxide Can prolonged exposure to trace levels of nitrous oxide in operating rooms and dental offices have a similar effect?
Jay B. Brodsky, M.D.
Stanford University School of Medicine, Stanford, CA 94305
Clin Toxicol (Phila). 2007;45(1):67-71.
Neurotoxicity of nitrous oxide: multimodal evoked potentials in an abuser.
Lin CY, Guo WYChen SP, Chen JT, Kao KP, Wu ZA, Liao KK.
Department of Neurology, Taipei Veterans General Hospital, Taipei, Taiwan.
INTRODUCTION:
Nitrous oxide (N2O) damages the nervous system of chronic abusers. Multimodal evoked potentials (EPs) can help document the electrophysiological abnormalities of N2O abusers and its distribution in the nervous system.
CASE REPORT:
A 41-year-old male N2O abuser had used N2O (4-5 cans/per day, about 2000 ml/can) for more than 10 years. He complained of progressive motor clumsiness and distal paresthesia in the four limbs. Abnormal laboratory tests were megaloblastic red blood cells (102.3 fL, normal 80-94 fL) and serum vitamin B12 concentration of 143 pg/nL (normal 160-970 pg/nL). An MR image did not show significant findings in the brain but demonstrated conspicuous changes in the posterior and lateral columns at the C2-C7 level, in accordance with the anatomical lesions of the subacute combined degeneration of the spinal cord. In addition to sensori-motor axonal polyneuropathy, multimodal EPs showed abnormal visual EPs with prolonged peak latencies of P100, abnormal brainstem auditory EPs characterized by delayed wave V and difficulty in the recognition of waves I and III, abnormal somatosensory EPs with significant decreased peak amplitudes of cortical potentials bilaterally, and abnormal motor EPs to transcranial magnetic stimulation with prolonged central motor conduction time.
CONCLUSION:
Our studies document electrophysiological abnormalities that may be attributed to N2O and indicate that N2O may indirectly involve multiple levels of the nervous system.
PMID:
17357386
Meyler’s Side Effects of Drugs - Nitrous oxide
The uptake of any other inhalation agent, given at the same time as nitrous oxide, is accelerated by the rate of uptake of nitrous oxide. This is termed the 'second gas effect'. Direct pharmacodynamic interactions do not occur. The addition of nitrous oxide to halothane in coronary patients was shown to produce hypotension with a subsequent risk of myocardial damage
The Pharmacology of Anaesthetic drugs; edited by Donald Eastwood; Clinical Anaesthesia Series; John Adriani M D - Nitrous Oxide
EFFECTS OF NITROUS OXIDE
There is some evidence that a tolerance to N2O develops after repeated or prolonged administration.
Clinical observations . . . of rats exposed . . . revealed that the animals remained relatively asleep and inactive for the first 12-24 hours, following which they could be more easily aroused and consumed more water and food.
Any user of N2O as an exhilarant can testify that a definite tolerance does in fact develop. After several long sessions, the user may find that as much as 35% more gas will be needed to reach the desired level of consciousness.
It must be stressed, however, that no withdrawal symptoms occur and tolerance in no way signifies dependence.
From an Internet site on nitrous oxide use
If you use an aerosol can, hold it upright and inject the gas directly into a balloon.
Don’t ever get into an enclosed space with nitrous oxide or you won’t get enough oxygen.
Don’t attempt to inhale standing up, you are quite likely to fall over and hurt yourself especially if you pass out.
Don’t ever breathe directly from a tank or can. The pressure on your lungs could do them permanent harm and as the gas expands it will cool and you could end up with frozen lips, frozen throat and frozen lungs – from which you could die.
A balloon filled with the gas is one of the safer ways of inhaling , you can’t overdose from a balloon.
Don’t ever smoke during the session – you may not get enough oxygen and will suffer from hypoxia.
Fast before the session and only drink water. There is the risk of vomiting if you indulge on a full stomach.
For every hit off the balloon take at least one breath of fresh air, don’t take one hit after another.
If you use a tank, keep it standing up, this way the gas will not be as cold as it enters the balloon.
If you use a can make absolutely sure that it is nitrous oxide and ONLY nitrous oxide in the can or propellant. A number of other harmful gases are occasionally used instead of nitrous oxide as a propellant and occasionally these are mixed with nitrous oxide. Freon for example, will have an effect but is as dangerous to your lungs liver and brain as glue fumes are.
The Pharmacology of Anaesthetic drugs; edited by Donald Eastwood; Clinical Anaesthesia Series
John Adriani M D - Nitrous Oxide
EFFECTS OF NITROUS OXIDE
BRAIN - N2O affects all modalities of sensation. Various mentation abilities are affected, such as short-term memory and concentration. Slightly distorted acuity of hearing, sight and touch occur. Overall electroencephalographic changes are slight.
INTRACRANIAL PRESSURE - No change without anoxia
TEMPERATURE REGULATING CENTER - Not affected according to Eastwood; slightly depressed during profound anaesthesia according to Adriani.
VASOMOTOR CENTER - Not affected without anoxia
RESPIRATORY CENTER – Not significantly affected without anoxia: slight increase in volume of respiration during administration of unsupplemented N2O
COUGH CENTER - Not affected; cough is moderately suppressed.
VOMITING CENTER - incidence variously reported. Nausea unusual without anoxia.
REFLEXES-VAGUS CENTER - Not affected.
REFLEXES-CAROTID BODY - Not affected.
REFLEXES CAROTID SINUS Not affected.
EYES - No effect on size of pupil. Pupils dilated with anoxia, but eyeballs remain active. Intra-ocular tension not affected. Tear secretion mildly depressed.
SALIVARY GLANDS - Insignificantly affected.
CILIA - Activity not decreased without anoxia.
HEART - Rate unaffected. Cardiac output unaffected. Coronary arteries, cardiac muscle, and automatic tissue unchanged. No appreciable electrocardiographic changes have been demonstrated as a result of nitrous oxide
BLOOD PRESSURE - Not affected without anoxia.
VENOUS PRESSURE - No elevation of central venous pressure has been demonstrated. Marked elevation if anoxia is present.
LUNGS – N2O does not irritate pulmonary epithelium. Respiratory movements are not depressed or exaggerated. Bronchial musculature is not affected.
METABOLISM - Not significantly changed.
DIAPHRAGM - Movements not affected.
ADRENAL - Not affected.
STOMACH - Gastric movements unchanged.
INTESTINES - Contractions increase slightly in amplitude and frequency.
LIVER - Functions are not affected unless anoxia is present.
KIDNEY - No significant effects, no significant alterations in volume or composition of urine
SPLEEN - Not affected.
UTERUS - Rhythmicity, tone or frequency of contractions not inhibited.
GENITALIA - no affects.
SKELETAL MUSCLES – increased muscle tone, apparently due to altered consciousness can occur
Internet site
Professionals, such as anesthesiologists or dentists, carefully mix it with oxygen and use pharmaceutical-grade gas. Others get it how they can: whippets, said to be fairly clean, or racing tanks, said to be technical-grade and to contain impurities. If you are fortunate enough to have a pharmaceutical tank, make the extra effort to get a scuba regulator. Whippets usually go into balloons.
The wah-wahs.
Never inhale gas directly from a tank or canister: expanding gas is very cold
(Charles's Law) and carl freeze your throat. Most of the (rare) injuries and fatalities associated with nitrous oxide use are from things like tanks falling over, people standing up and falling over unconscious, dropped cigarettes - from stupid things like that. Or even more stupid, people putting bags over their heads, or turning on a tank in an enclosed space, and then dying of anoxia.
Nitrous oxide supports combustion as well as oxygen does, in matters of open flame, but that does not go for your bodily respiration. you still need oxygen.
Be sure you get it.
From Laughing gas – nitrous oxide – edited by Michael Shedlin and David Wallechinsky
To avoid the hazards involved in nitrous oxide inhalation, the EBCPS has formulated several safety precautions.
The main danger is that the user will render himself "unconscious" and will continue to inhale pure nitrous without oxygen. This serious circumstance can be easily avoided: Never attach the source of the gas to the mouth or nose under any conditions. The safety valve in auto-administration is the fact that the source of the gas falls away when the user momentarily passes out, allowing him/her to breathe vital atmospheric air. If a flexible tube such as a garden hose is connected to the tank, three adverse conditions occur.
- First, undue pressure is put on the lungs by the rushing gas;
- Second, the throat and lips can freeze
- And third, only one person can hit on the gas at a time.
An extremely satisfying alternative to a direct hose approach is the balloon method. Large "party" or "weather" balloons are filled from the tank; the balloons become conveniently portable containers, can be passed like joints, and allow for simultaneous inhalation by a large group of persons. In addition, the balloon method wastes little gas.
The optimum physical environment for the inhalation of nitrous oxide is a soft place – cushions, mattresses, thick carpets, perhaps a fern meadow or a freshly ploughed field. People occasionally, fall or pitch about or slump heavily. lf one finds it desirable to stand up or walk while inhaling, it is recommended that extreme caution be employed, and, if possible a partner be secured.
Nausea is periodically reported, and it is difficult to tell whether or not a full stomach contributes to such discomfort. It is recommended, however, that users avoid large meals directly before a gas session.
There are less technical problems if the tank is standing up - the liquid nitrous is farther from the valve, the freezing area on the tank is reduced.
Casual deep breathing between hits of gas is a healthy policy. This increases the amount of oxygen in the system.
Cigarettes are often dropped or miswielded under the influence and frequently pop precious balloons
Filling up a small enclosed area like a closet or a car with pure nitrous oxide can be lethal.
Nitrous oxide is safe if used sensibly.
Take care of your brain.
From Laughing gas – nitrous oxide – edited by Michael Shedlin and David Wallechinsky
In its medical capacities, nitrous oxide is a powerful analgesic (pain killer) and a weak anaesthetic and must be breathed in large quantities to effect general anaesthesia. It has a potency of 25% when compared to a drug the potency of diethyl ether.
Nitrous oxide is usually administered with 20-35% oxygen, and can be inhaled for extended periods of time provided the patient is given enough oxygen. For major surgery, the patient is generally put to sleep before N2O administration, with pentothal or a similar sedative, but unsupplemented N2O can be used for a variety of operations in which minimal muscular relaxation is required: dental extractions and drainage of abscess, breast biopsy, uterine curettage, vaginal plastic repair, and as an analgesic in obstetrics. Pure nitrous oxide is often administered for brief dental operations.
Induction of and recovery from nitrous oxide are quite rapid; the gas takes effect almost immediately, and fades out of the system in less than a half hour. The actual high lasts one or two minutes.
Nitrous oxide itself is a harmless and innocuous substance. The principal, if not the only danger related to its use is oxygen deprivation (anoxia, hypoxia, asphyxia). Severe decerebration and even death can result from oxygen lack, although the death percentage throughout twenty decades of medical N2O use is infinitesimal[ly small]').
Observations
For iPad/iPhone users: tap letter twice to get list of items.