[Narcotic gas burden of personnel in pediatric anesthesia]

Suitability of the Limit Dose in Evaluating Reproductive Toxicity of Substances and Preparations

An oral dose of 1000 mg/kg body weight/day is mentioned in Organisation for Economic Cooperation and Development (OECD) and European Union (EU) guidelines as a default maximum dose in limit tests for studies on reproductive toxicity. This paper investigated whether upper range human exposure data from the workplace are supportive of this limit dose as an upper limit of possible human exposure. To this end, published exposure data as well as data from the database MEGA of the German “Berufsgenossenschaften” were evaluated. These data indicate that exposure concentrations in the range of 500 to 2000 mg/m3 (time-weighted averages) can be considered high human exposures to volatile compounds. Inhalation exposure to aerosols and dermal exposure result in lower dose levels. By applying suitable extrapolation factors, it was concluded that occupational exposures up to 325 mg/m3 can reliably be assessed with limit tests using a dose level of 1000 mg/kg/day. The limit dose has been proposed for use in the EU as a starting point to derive specific concentration limits for hazard classification of preparations containing reproductive toxicants, with the objective to consider the potency of the substances. This analysis shows that for some groups of chemicals, instead of the limit dose, the putative maximum levels of human exposure should be taken into account when deriving concentration limits for the classification of preparations. Furthermore, possible deviations from a linear correlation between concentration in the preparation and exposure should be considered.

Persistent cognitive functioning deficits in operating rooms: two cases

BACKGROUND

To date, chronic toxic encephalopathy (CTE) has never been described in operating room personnel.

CASE REPORT

We report two cases of anaesthetists who developed this pathology. They have both used anaesthetic gases for many years in paediatric surgery. Air conditioning was deficient during three years in operating rooms and atmospheric anaesthetics concentration was high (N(2)O mean concentration: 311 ppm, peak levels 1,600 ppm; halogenated: 16 ppm, peak levels: 1,600 ppm).

CLINICAL SYMPTOMS

Mood troubles and non-specific neuropsychic deficits gradually evolved until they had to stop working. Neuropsychological assessment showed important deficits in attention, executive functioning, short-term memory and visuo-spatial organization. Blood tests, VEPs, MRI, neuroSPECT and cardiovascular exams were normal. Troubles had slowly improved after cessation of exposure and sequels still remain.

CONCLUSION

These CTE cases seem to be the consequence of a long-term exposure to important levels of anaesthetic gases, and particularly nitrous oxide. It points out the importance of preventive measures in operating rooms, where occupational hazards are varied.

Exposition des Personals gegenüber Sevofluran

BACKGROUND

Occupational exposure to volatile anaesthetics cannot be completely avoided even in modern operating theatres. In 1997, the staff exposure during balanced anaesthesia in our hospital was low (sevoflurane 0.49 ppm; N(2)O 11.5 ppm). In 1999, N(2)O was completely omitted at our hospital, therefore, exposure to volatile anaesthetics, namely sevoflurane, might have increased.

METHODS

Environmental exposure was measured by photoacoustic infrared spectrometry. To determine the personal exposure and to compare it with environmental exposure, 14 anaesthetists wore diffusion samplers near their breathing zones for 1 week.

RESULTS

The median environmental concentration of sevoflurane was between 0.09 and 0.21 ppm in central operating theatres and between 0 and 24.8 ppm in intervention rooms. The median personal concentration was 0.19 ppm.

CONCLUSION

The occupational exposure to volatile anaesthetics is not higher using sevoflurane alone compared to the combination of sevoflurane and N(2)O. In addition, the data acquired from environmental and personal measurements showed similar results.

Scavenging in the operating room

PURPOSE OF REVIEW

The use of inhalation general anesthetic gases has led to contamination of the operating room environment. Chronic exposure to these agents has been associated with a number of adverse health effects. Controversy remains with regard to these health effects, and whether further reducing the level of operating room contamination should be a high priority. Current methods are outlined by which anesthetic waste gases contaminate and are removed from the operating room. These controversies are explored in the light of recent research.

RECENT FINDINGS

Recent work employing genotoxicity studies suggests that National Institute for Occupational Safety and Health recommendations may be appropriate to protect healthcare workers. New developments over the past year include the suggestion of employing devices such as the Anesthetic Scavenging Hood (ASH), SiBI tube connector and mask stopper. The use of these devices, in concert with efficient anesthesia machine scavenging, may further reduce operating room contamination.

SUMMARY

The National Institute for Occupational Safety and Health calls for lower levels of exposure when compared with those found in European standards. It may be appropriate for European guidelines to be re-addressed; however, more conclusive studies need to be undertaken to identify the precise effects of these agents at a given exposure level. It may also be appropriate to expand the arena of monitoring and scavenging to all areas where inhalation anesthetics are used or emitted, such as in the post-anesthesia care unit and research laboratory settings.

Occupational risk in health care and research

BACKGROUND

Working in the health care and research sectors has been linked to various hazards.

METHODS

Studies published in the peer-reviewed literature that are pertinent to the exposures or diseases relevant to these fields were reviewed.

RESULTS

The most important exposures include infectious agents, formaldehyde, anesthetic agents, antineoplastic drugs, and ethylene oxide. The best-documented evidence is that of infectious risk primarily among clinical personnel. Monitoring studies of persons occupationally exposed to anesthetics clearly demonstrate behavioral effects, possible risk of reproductive problems, as well as cytogenetic effects of unknown significance. The latter two impairments are also observed among those exposed to antineoplastic drugs and ethylene oxide. Exposure to formaldehyde appears to be associated with nasopharyngeal tumors. Whereas increased risk of cancer of certain sites, particularly the brain and lymphohematopoietic system, is found among research and health care personnel, no specific exposure has been linked to these neoplasms.

CONCLUSIONS

Although some results are inconsistent, continued environmental and biological monitoring will allow better assessment of exposures and of implemented protection measures.

The use of a uniquely designed anesthetic scavenging hood to reduce operating room anesthetic gas contamination during general anesthesia

Numerous studies have suggested that chronic exposure to trace levels of anesthetic gas is harmful to operating room (OR) personnel. In the delivery of pediatric general anesthesia, an uncuffed endotracheal tube (ETT) is normally used which can result in considerable volatile anesthetic and nitrous oxide contamination of the OR. In this report, we present a method to reduce exposure to these anesthetic gases by means of an anesthetic scavenging hood (ASH). The ASH was used on six pediatric patients undergoing general endotracheal anesthesia via an uncuffed ETT. Measurements of all ambient gas levels were made 6 in. horizontally from the patient's ear and 6 in. from the table surface. The application of the vacuum source to the ASH resulted in a very significant (P < 0.01, paired t-test) decrease in levels of ambient anesthetic gas, with no measurable change in ventilatory variables or changes in body temperature (P > 0.05, paired t-test). Discontinuation of the vacuum force to the ASH resulted in a marked increase in ambient levels of anesthetic gas. We conclude that the ASH is extremely effective in reducing waste anesthetic gas associated with anesthesia administered via an uncuffed ETT. The ASH may be a valuable and cost-effective addition in the OR for both reducing ambient anesthetic waste gas levels and conserving patient heat.

IMPLICATIONS

Chronic exposure to trace levels of anesthetic gas is harmful to operating room personnel, especially in the delivery of pediatric general anesthesia via an uncuffed endotracheal tube. The anesthetic scavenging hood is a cost-effective and efficient method to reduce these waste anesthetic gases, and it offers patient heat conservation.

Occupational exposure to volatile anaesthetics: epidemiology and approaches to reducing the problem

Long term occupational exposure to trace concentrations of volatile anaesthetics is thought to have adverse effects on the health of exposed personnel. In contrast with halothane--an agent likely to cause mutagenic effects and proven to be teratogenic--isoflurane and enflurane have not so far been proved to have adverse effects on the health of personnel exposed long term. Data on the newer agents sevoflurane and desflurane are limited. Since possible health hazards from long term exposure to inhalational anaesthetics cannot yet be definitively excluded, many Western countries have established limits for exposure. These usually range from 2 to 10 ppm as a time-weighted average over the time of exposure. A number of investigations have demonstrated that, in operating theatres with modern climate control and waste anaesthetic gas scavenging systems, occupational exposure is unlikely to exceed threshold limits. However, occupational exposure from the use of volatile agents in operating theatres with poor air control--especially during bronchoscopy procedures in paediatric patients--remains a source of concern. This also holds true for both postanaesthesia care units (PACU) and intensive care units (ICU) lacking proper air conditioning and waste gas scavengers. To minimise occupational exposure to volatile anaesthetics, all measures must be taken to provide climate control and properly working scavenging devices, and ensure sufficient personal skill of the anaesthetist, e.g. during inhalational mask induction. Furthermore, low-flow anaesthesia should be used whenever possible. The sole use of intravenous drugs such as propofol instead of volatile agents, were this possible, would eliminate occupational exposure, but may result in environmental pollution by toxic metabolites (e.g. phenol).

Occupational exposure to inhaled anaesthetics: a follow-up study on anaesthetists of an eastern European university hospital

BACKGROUND

Although no dose-response relationship for the health risks associated with the occupational exposure to inhaled anaesthetics exists, public health authorities recommend threshold values. The aim of the present study was to assess if and to what extent these threshold values are exceeded in an eastern European university hospital before and after measures had been taken to reduce occupational exposure.

METHODS

At nine workplaces occupational exposure of anaesthetists to nitrous oxide and halothane or isoflurane was measured by means of photoacoustic infrared spectrometry. The measurements were carried out in 1996 and were repeated in 1997 after the installation of active scavenging devices at five workplaces and an air-conditioning system at one workplace.

RESULTS

Occupational exposure to nitrous oxide and halothane or isoflurane was lower in 1997 compared to 1996. In 1997 most of the nitrous oxide values still exceeded the threshold value of 100 ppm, whereas most of the halothane and isoflurane values were already below the threshold values of 5 ppm and 10 ppm in 1996.

CONCLUSION

The measures taken were effective in reducing waste gas exposure. Nevertheless, further efforts are necessary, especially for nitrous oxide, to reach western European standards. These efforts comprise structural measures such as active scavenging devices and air-conditioning systems at all workplaces, the use of total intravenous anaesthesia, low-flow anaesthesia and an appropriate working technique.

Effects of gas flow management on postintubation end-tidal anesthetic concentration and operating room pollution

STUDY OBJECTIVE

To study how different anesthetic practices during the transition from anesthetic delivery by mask to endotracheal intubation affect end-tidal postintubation anesthetic concentration and operating room (OR) pollution.

DESIGN

Prospective study.

SETTING

Anesthesia research laboratory.

MEASUREMENTS AND MAIN RESULTS

We studied four gas flow management practices: practice vaporizer off, only the anesthetic vaporizer was turned off; all off, oxygen (O2), nitrous oxide (N2O), and the vaporizer were turned off; gas off: O2 and N2O were turned off; and all on: neither the gas flows nor the vaporizer were turned off. A model of inhalational anesthetic induction was simulated by using an adult circle system attached to a reservoir bag ("artificial lung"). By using a fixed gas flow, we achieved an end-tidal N2O (ETN2O) concentration of 70% and end-tidal halothane (ETHal) concentration of 3%, then stopped mechanical ventilation and performed the four practices for a 30-second "intubation" period. During this time, the reservoir bag was disconnected from the circuit, and the gas volume exiting the circuit (pollution volume) was measured. After this 30-second disconnect period, the bag was reconnected to the anesthetic circuit, and the original ventilation, gas flows, and vaporizer setting were resumed. The anesthetic concentrations were measured at 10, 20, and 30 seconds after reconnection. For the vaporizer off practice, ETHal was low and did not return to equilibrium within 30 seconds (p < 0.05); ETN2O clinically was unaltered. In the all off practice, anesthetic concentrations were below equilibrium at 10, 20, and 30 seconds (p < 0.05). For the gas off practice, ETHal was slightly below equilibrium at all times; ETN2O was below equilibrium at 10, 20, and 30 seconds (p < 0.05). In the all on practice, end-tidal anesthetic concentrations were unchanged when compared with equilibrium (p > 0.05). Pollution volumes in the vaporizer off and all on practices were ten-fold higher than in the all off and gas off practices (p < 0.05).

CONCLUSION

In a mechanical model of anesthetic induction, turning the gas flows off before "intubation" and leaving the vaporizer on (the gas off practice) maintained "postintubation" end-tidal drug concentrations close to "preintubation" equilibrium and minimized OR pollution.

Measurement and reduction of nitrous oxide in operating rooms

In a program designed to lower exposure to anesthetic gases, nitrous oxide in the breathing zone of anesthesiologists was continuously monitored by means of a direct reading apparatus and a specially designed collar. Initially, the average concentration during anesthesia in intubated patients, determined in 30 operating rooms of seven hospitals, was 68 ppm. During mask anesthesia in children, it was 407 ppm (nine operating rooms, nine hospitals). The main hygienic measures were: a check of the anesthesia apparatus, improvement of the general ventilation in the operating room, and the application of a "double mask." With a combination of measures, the concentration during anesthesia in intubated patients was reduced from 61-90 ppm to 2-15 ppm. During mask anesthesia in children, the concentration decreased from 134-764 ppm to 9-42 ppm. The monitoring system used reveals important differences in the exposure during the separate phases of the anesthesia (induction, maintenance, and extubation). It also indicates which factors determine the exposure of the anesthetist and allows accurate determination of the personal exposure.