A comparison of sister chromatid exchanges in lymphocytes of anesthesiologists to nonanesthesiologists in the same hospital

An increased incidence of sister chromatid exchanges (SCEs) in peripheral lymphocytes of operating room personnel exposed to waste anesthetic gases has been reported. We investigated whether the increase of SCEs in anesthesiologists was reversible. Twenty-five anesthesiologists exposed to waste anesthetic gases such as sevoflurane and nitrous oxide were compared with nonexposed internists working in the same hospital. The concentrations of sevoflurane and nitrous oxide in the operating rooms were measured. The incidence of SCE was measured in lymphocytes cultures of anesthesiologists before and after a 2-mo leave from the operating room. These values of SCE were compared with those of nonexposed physicians. Occupational exposure to sevoflurane and nitrous oxide in the operating rooms were above the threshold values. There was a significant difference in SCE values of the anesthesiologists compared with the nonexposed physicians (11.9 +/- 4.4 versus 4.2 +/- 1.1, P < 0.001). After a 2-mo leave from the operating room, the SCE values of the anesthesiologists were significantly lower compared with those taken before the leave (4.8 +/- 1.8 and 11.9 +/- 4.4, respectively, P < 0.001). We conclude that the increase of SCE in anesthesiologists exposed to increased environmental concentrations of waste anesthetics gases, such as sevoflurane and nitrous oxide, are reversible if they work free from exposure for 2 mo.     

Operating Room Nurses'' Psychomotor and Driving Skills after Occupational Exposure to Halothane and Nitrous Oxide

Concentrations of halothane and nitrous oxide were assayed by gas chromatography throughout a working day in three operating theatres and in the end-tidal air of 19 nurses 15 and 60 min after leaving the theatres. Perceptual, psychomotor and driving skills were measured in these nurses and in 11 younger nurses working in the wards of the same hospital. A complicated psychomotor test battery and a driving simulator were used. End-tidal air concentrations of halothane and nitrous oxide were positively correlated with the exposure level of these gases in the operating theatres. Some of the operating room nurses had greater amounts of halothane in their end-tidal air (average 15 to 10 ppm) than student volunteers 4.5 h after 3.5 min of general anaesthesia with a combination of halothanenitrous-oxide oxygen (10 ppm halothane). These volunteers had worse psychomotor and driving performances when measured than controls who had not been anaesthetized. No correlations were found between the concentrations of halothane or nitrous oxide in end-tidal air and psychomotor or driving performance. Despite their higher age and exposure to the operating room environment, the driving skills of the operating room nurses were similar to those of the ward nurses. The results suggest that tolerance to anaesthetic gases develops among operating room personnel. No impairment of driving skills can be expected after daily exposure to halothan and nitrous oxide among long-term employees in operating theatres.     

Nitric oxide delivery to the lung: a model

Dedicated nitric oxide equipped ventilators are now available commercially but are not yet common in clinical practice. With other ventilators, there is no standardized procedure for the administration or monitoring of nitric oxide. We describe the use of nitric oxide in conjunction with a simple time-cycled, pressure regulated, flow generating ventilator attached to a model infant-sized lung. The measured nitric oxide concentrations were always less than calculated. Infusion site, minute ventilation and sampling port all affected nitric oxide concentration (P < 0.05). Increasing minute ventilation lowered measured nitric oxide concentration exponentially. Mixing of gases improved when nitric oxide was infused closer to the ventilator. Acid contamination was found in water samples from humidifier, water trap and ventilator gas outlet. Acidification was reduced, without change in measured nitric oxide delivery, when infused prehumidifier. We recommend, when used as therapy, nitric oxide levels in inspired gases should always be measured.     

Explosion des gaz intestinaux en cours d''opération

Two cases of colonic gas explosion during surgery are reported. The treatment of the lesions required a partial colectomy in one case and a total colectomy in the other case. The different factors involved in such accidents are discussed. Three factors are necessary to trigger off an explosion of intestinal gases: the presence of combustible gases (hydrogen, methane), the presence of combustive gases (oxygen, nitrous oxide) and an initiating heat source (endoscopic or surgical electrocautery). The mannitol used for bowel cleansing undergoes partial colonic bacterial fermentation increasing the intraluminal concentration of hydrogen. During anaesthesia the oxygen-nitrous oxide mixture increases the intestinal concentration of these two major combustive gases. Electrocautery provides the spark triggering the explosion. The use of mannitol for colonic preparation should be questioned; the use of electrocautery to open the colon is advised against.     

THE IMMEDIATE CARDIAC DEPRESSION BY ANAESTHETICS IN CONSCIOUS DOGS

The time course of circulatory changes during induction withhalothane and/or nitrous oxide was studied in six healthy awakedogs. Beat-to-beat changes in cardiac performance were measuredwith chronically implanted aortic electromagnetic flowmeters,and pressures were recored from atria, pulmonary artery, anddescending aorta. The dogs were trained to wear masks designedfor delivering gases, and to acclimatize to the odour of halothane.Both 3 per cent halothane and 60 per cent nitrous oxide reducedpeak aoritc flow and maximum acceleration within 4–8 secondsafter the first breath. This depression was more pronouncedwith halothane than nitrous oxide, and was even more severewith the combinaton of halothane and nitrous oxide, and waseven more severe with the combination of halothane and nitrousoxide. and was even more severe with the combination of halothaneand nitrous oxide. Cardiac denervation when halothane and nitrousoxide olone and in combination produced the same immediate cardiacdepression ^*Supported in part by United States Public Health,Grant Number2T01GM00063-09 and the WellcomeTrust. Present address: Departmentof Anesthesia,Stanford Medical School, Palo Alto, California,U.S.A.     

BACTERIAL CONTAMINATION OF ANAESTHETIC GASES

The bacterial content of oxygen and nitrous oxide immediatelybefore and after passing through clean and used breathing systems(circuits) was measured using a specially constructed agar chamber(Bourdillon's slit sampler). The content per litre of oxygenfrom the outlet of the anaesthetic machine was 4.0 x 10^-2, and2.9 x 10^-2 for nitrous oxide, corresponding to 3.5 x 10^-2 fora 50% mixture of the gases. After passing through cleaned circuits,the bacterial pollution of the gas mixture had increased by30%, but more than elevenfold after passing through used circuits.The content from cleaned circuits was less than that measuredpreviously in the air of hospital wards and operating theatres,whereas gases from used circuits were polluted to approximatelythe same extent. It is concluded that used circuits may increasethe risk of cross-infection. The cleaning method employed byus (dish-washer-hot air drying) appeared to be acceptable. Reprint requests to H. N.     

Special article: general anesthetic gases and the global environment

General anesthetics are administered to approximately 50 million patients each year in the United States. Anesthetic vapors and gases are also widely used in dentists' offices, veterinary clinics, and laboratories for animal research. All the volatile anesthetics that are currently used are halogenated compounds destructive to the ozone layer. These halogenated anesthetics could have potential significant impact on global warming. The widely used anesthetic gas nitrous oxide is a known greenhouse gas as well as an important ozone-depleting gas. These anesthetic gases and vapors are primarily eliminated through exhalation without being metabolized in the body, and most anesthesia systems transfer these gases as waste directly and unchanged into the atmosphere. Little consideration has been given to the ecotoxicological properties of gaseous general anesthetics. Our estimation using the most recent consumption data indicates that the anesthetic use of nitrous oxide contributes 3.0% of the total emissions in the United States. Studies suggest that the influence of halogenated anesthetics on global warming will be of increasing relative importance given the decreasing level of chlorofluorocarbons globally. Despite these nonnegligible pollutant effects of the anesthetics, no data on the production or emission of these gases and vapors are publicly available. The primary goal of this article is to critically review the current data on the potential effects of general anesthetics on the global environment and to describe possible alternatives and new technologies that may prevent these gases from being discharged into the atmosphere.     

THE EFFECT OF VARIOUS CONCENTRATIONS OF NITROUS OXIDE ON THE 24-HOUR EXPLANTED CHICK EMBRYO

The effects of nitrous oxide on the early explanted chick embryowere investigated using the technique of New (1955). After 22hours incubation the embryos were explanted and exposed fora further 24 hours to the following gases: air, nitrous oxide(25 per cent), nitrous oxide (60 per cent), nitrous oxide (79per cent). The oxygen concentration was maintained at normallevels (20.9 per cent) and the balance of the gases was nitrogen.In a fifth trial a 60 per cent nitrous oxide 40 per cent oxygenmixture was used. After exposure the embryos were examined underthe dissecting microscope and in histological sections. Theserevealed no effect on the chick embryo after treatment withnitrous oxide for 24 hours.     

Medical gases,their storage and delivery

Medical gas production, storage and delivery is a complex process. Design of such a system must ensure that gas delivery is safe, convenient and cost-effective. This article reviews the production, storage and delivery of commonly used anaesthetic gases, following the gases from production to delivery.     

Pollution of the medical air at a university hospital in the metropolitan Tokyo area

STUDY OBJECTIVE: To investigate the quality of medical air in a hospital in the metropolitan area.DESIGN: Prospective study. SETTING: University hospital in the metropolitan Tokyo area. INTERVENTIONS: Medical air introduced into a bio-clean operating room was sampled. MEASUREMENTS: The concentrations of nitric monoxide (NO), nitrogen dioxide (NO(2)), sulfur dioxide (SO(2)), and carbon monoxide (CO) in the medical air were measured every 30 minutes for 15 days. MAIN RESULTS: The concentrations (mean +/- SD) of NO, NO(2), SO(2), and CO were 34.4 +/- 35.0 ppb (range 0-200 ppb), 7.7 +/- 5.5 ppb (0-29 ppb), 33.8 +/- 2.9 ppb (21-46 ppb), and 1.65 +/- 0.87 ppm (0.5-7.5 ppm), respectively. The concentrations of these gases peaked at rush hours within a day. CONCLUSIONS: In the metropolitan area, we occasionally provide our patients with medical air of poor quality.     

Carbon dioxide field flooding: a retrospective study

The carbon dioxide surgical field flooding technique has long been tried with varying degrees of success. A recent revival of the technique that began over 40 years ago in cardiac surgery, has brought promise as well as improved results attributable to improved technology. Studies at JFK Medical Center have been very successful using the carbon dioxide surgical field-flooding technique. Establishing new guidelines will assist other institutions in attempting this "old" technique with renewed success. Modern, more efficient equipment make use of carbon dioxide to displace intracardiac gases a safe procedure. The carbon dioxide field-flooding technique is safer, easier, and more efficacious than traditional de-airing techniques. This study shows that a long-standing procedure is valuable by observing the results, and, retrospectively evaluating stroke rates among cardiac valve cases at the hospital.     

The Effect of Local Scavenging on Occupational Exposure to Nitrous Oxide

Despite evacuation of excess anaesthetic gases at the expiratory valve of the anaesthetic circuit and a general ventilation system producing 17–20 air changes per hour, mask anaesthesia often causes occupational exposure to anaesthetic gases exceeding the threshold limit values. The effect of a local air exhaust system, a local scavenger, on occupational exposure to nitrous oxide during paediatric mask anaesthesia was studied. The scavenger evacuated 140 m³ of air per hour and was placed at a distance of 20 cm from the face mask. In a very poorly ventilated operating theatre the exposure to nitrous oxide was reduced by 75% during the anaesthetic sessions and exposure to concentrations above 500 ppm was almost eliminated. The experiences from the installation and clinical use are discussed. Local scavenging is an excellent complement to the scavenging of excess gases at the expiratory valve, and it may be considered an alternative to expensive, high-capacity ventilation systems.     

Trace nitrous oxide levels in the postanesthesia care unit.

The effect of trace levels of waste anesthetic gases on the health of postanesthesia care unit (PACU) nurses who work in an unscavenged environment has been questioned, although it seems likely that levels of trace gases in the PACU would be much lower than those in the operating room. In this study, we documented nitrous oxide levels in the ambient air of two large PACUs. Nitrous oxide levels were measured using a time-weighted average monitor worn by 33 PACU workers at two different hospitals for the duration of their shifts. On the same day, patient data were collected at the time of admission to the PACU. Data included age and weight of the patient, type of surgery, anesthetic technique, and end-tidal level of nitrous oxide immediately before the patient left the operating room. The mean time-weighted average nitrous oxide level in PACU A was 2.0 ppm (range 0-6.4); in PACU B, it was undetectable, i.e., < 2.0 ppm. Levels of nitrous oxide to which PACU patient care personnel are exposed are well below the National Institute of Occupational Safety and Health and Occupational Health and Safety Administration recommended exposure level of 25 ppm measured for the duration of anesthetic administration. Implications: Our results indicate that the levels of nitrous oxide in postanesthesia care units with well maintained, modern ventilation systems are very low. Previous research suggests that the health of workers exposed to these levels should not be adversely affected.     

Experimental and Preliminary Clinical Studies of a Method of Reducing Anaesthetic Gas Contamination

Long-term exposure to low concentrations of anaesthetic gases is potentially hazardous. In spite of efforts to reduce the exposure of personnel by increased air conditioning, by scavenging of excess circuit gases and by improvements in anaesthetic equipment, high concentrations of gases have still been measured. Problems arise during mask induction, in paediatric anaesthesia, and in certain situations with unavoidable leaks, especially in small rooms but also in recovery rooms. Experimental and preliminary clinical studies have shown that nitrous oxide pollution can be considerably reduced by using a separate close scavenging system in the area where high gas concentrations occur. The geometrical and flow dimensions of a close scavenging device used in paediatric. anaesthesia are described.     

A study of mixing conditions during nitric oxide administration using simultaneous fast response chemiluminescence and capnography

We have evaluated the mixing properties of nitric oxide in inspired gases for five different administration techniques. Nitric oxide and carbon dioxide were delivered to the ventilator system before the ventilator or after the ventilator as a continuous flow, either directly into the inspiratory limb or into a mixing chamber positioned in the inspiratory limb. Both gases were delivered as above but synchronized with inspiration. Mixing conditions were evaluated using fast response chemiluminescence for nitric oxide and capnography for carbon dioxide analysis. Administration of nitric oxide and carbon dioxide directly into the inspiratory limb as a continuous flow or with a magnetic valve-controlled synchronized flow resulted in peak concentrations of 236% and 220%, respectively, of expected values. The use of a mixing chamber reduced these values to 104% and 102%, respectively. Administration of nitric oxide as a continuous flow into the tubing of an intermittent flow ventilator resulted in highly fluctuating inspiratory peak concentrations, which could be avoided with a mixing chamber.      

A SYSTEM OF DIFFERENTIAL DELIVERY PRESSURES AND HOSE DIAMETERS FOR USE IN HOSPITAL MEDICAL GAS INSTALLATIONS

Medical gases can be identified simply if they are suppliedat different pipeline pressures. Routine maintenance errors,accidental pipeline cross-connections, or gas failures, canbe automatically detected by incorporating a pneumatic unitwith pressure-sensitive valves into the anaesthetic machine.A fall-iafe method of ensuring the delivery of the correct gasesto the patient is described.     

Respiratory syndromes in acute poisoning

Respiratory syndromes in acute poisoning can refer to a wide range of specific clinical syndromes, from acute tracheobronchitis to acute pulmonary edema, chemical pneumonia, acute respiratory distress syndrome and respiratory failure, that occur as a result of direct or indirect effect of chemical substances, drugs and toxins on lungs and airways. Our study attempt to identify, during one-year retrospective study on patients diagnosed with acute poisoning, addressed to Medical Clinic of Emergency Clinic Hospital of Iasi, the respiratory syndromes commonly associated with acute poisoning. We found that the association of toxins, inhalation of gases or volatile substances have a high risk for appearance of respiratory syndromes. The outcome of these patients is influenced by the duration of exposure or the delay of presentation to the hospital after ingestion, and depends on the rapid and aggressive measures for basic life support and intensive care.     

Laryngeal mask and anaesthetic waste gas exposure

In recent years there has been a growing awareness of the possible hazards caused by anaesthetic gases in operating theatres. The laryngeal mask airway provides an alternative both to tracheal intubation and the face mask although the implications for operating theatre contamination have not been quantified. This paper describes the incidence and magnitude of exposure of theatre personnel to waste anaesthetic gases during laryngeal mask airway anaesthesia. The leakage of anaesthetic gases to the anaesthetist's breathing zone was monitored using a Bruel & Kjaer Multi Gas Monitor, Type 1302 during 50 general anaesthetics employing either spontaneous (n = 24) or controlled (n = 26) ventilation. All patients were anaesthetised with propofol, alfentanil and nitrous oxide. There was no statistically significant association between the amount of anaesthetic gas leakage and ventilation method. The laryngeal mask airway meets occupational safety requirements on nitrous oxide concentrations in the operating theatre environment.     

Anesthetic and perioperative management of 1000 cases of congenital heart surgery--massive vasodilator therapy and early extubation

We report our anesthetic and perioperative management of 1000 cases of congenital heart surgery in Okayama University Medical School over the last six and a half years. Most of these patients were anesthetized by fentanyl and all patients were managed in our ICU postoperatively. Although hospital death rate in all patients was 4.5%, almost half of dead patients were patients with hypoplastic left heart syndrome. Neonatal mortality rate has been still high, 18.9%, which has been our main problem. We tried to extubate patients with complex congenital heart diseases earlier postoperatively for the last three years, using massive dose of vasodilators without nitric oxide.     

INDIRECT DETERMINATION OF THE IDEAL ALVEOLAR OXYGEN TENSION DURING AND AFTER NITROUS OXIDE ANAESTHESIA

The conventional form of the alveolar air equation assumes thatinert gases are in equilibrium. It is therefore inapplicableduring nitrous oxide uptake and elimination. An alternativeform of the equation avoids this assumption and may be usedfor calculation of the ideal alveolar tension of oxygen or inhalationalanaesthetic agents.