Low flow anaesthesia reduces occupational exposure to inhalation anaesthetics. Environmental and biological measurements in operating room personnel

Reducing the environmental impact of mask inductions in children: A quality improvement report

BACKGROUND

Inhalational anesthetic agents are potent greenhouse gases with global warming potential that far exceed that of carbon dioxide. Traditionally, pediatric inhalation inductions are achieved with a volatile anesthetic delivered to the patient in oxygen and nitrous oxide at high fresh gas flows. While contemporary volatile anesthetics and anesthesia machines allow for a more environmentally conscious induction, practice has not changed. We aimed to reduce the environmental impact of our inhalation inductions by decreasing the use of nitrous oxide and fresh gas flows.

METHODS

Through a series of four plan-do-study-act cycles, the improvement team used content experts to demonstrate the environmental impact of the current inductions and to provide practical ways to reduce this, by focusing on nitrous oxide use and fresh gas flows, with visual reminders introduced at point of delivery. The primary measures were the percentage of inhalation inductions that used nitrous oxide and the maximum fresh gas flows/kg during the induction period. Statistical process control charts were used to measure improvement over time.

RESULTS

33 285 inhalation inductions were included over a 20-month period. nitrous oxide use decreased from 80% to <20% and maximum fresh gas flows/kg decreased from a rate of 0.53 L/min/kg to 0.38 L/min/kg, an overall reduction of 28%. Reduction in fresh gas flows was greatest in the lightest weight groups. Induction times and behaviors remained unchanged over the duration of this project.

CONCLUSIONS

Our quality improvement group decreased the environmental impact of inhalation inductions and created cultural change within our department to sustain change and foster the pursuit of future environmental efforts.

Occupational Exposure to Halogenated Anaesthetic Gases in Hospitals: A Systematic Review of Methods and Techniques to Assess Air Concentration Levels

Objective During the induction of gaseous anaesthesia, waste anaesthetic gases (WAGs) can be released into workplace air. Occupational exposure to high levels of halogenated WAGs may lead to adverse health effects; hence, it is important to measure WAGs concentration levels to perform risk assessment and for health protection purposes. Methods A systematic review of the scientific literature was conducted on two different scientific databases (Scopus and PubMed). A total of 101 studies, focused on sevoflurane, desflurane and isoflurane exposures in hospitals, were included in this review. Key information was extracted to provide (1) a description of the study designs (e.g., monitoring methods, investigated occupational settings, anaesthetic gases in use); (2) an evaluation of time trends in the measured concentrations of considered WAGs; (3) a critical evaluation of the sampling strategies, monitoring methods and instruments used. Results Environmental monitoring was prevalent (68%) and mainly used for occupational exposure assessment during adult anaesthesia (84% of cases). Real-time techniques such as photoacoustic spectroscopy and infrared spectrophotometry were used in 58% of the studies, while off-line approaches such as active or passive sampling followed by GC-MS analysis were used less frequently (39%). Conclusions The combination of different instrumental techniques allowing the collection of data with different time resolutions was quite scarce (3%) despite the fact that this would give the opportunity to obtain reliable data for testing the compliance with 8 h occupational exposure limit values and at the same time to evaluate short-term exposures.

Environmental and biological measurements of isoflurane and sevoflurane in operating room personnel

PURPOSE

The present study aimed to compare the concentration of isoflurane and sevoflurane in the individual's breathing zone and ambient air of operating rooms (ORs), to investigate the correlation between breathing zone levels and urinary concentrations, and to evaluate the ORs pollution in the different working hours and weeks.

METHODS

Environmental and biological concentrations of isoflurane and sevoflurane were evaluated at 9ORs. Air samples were collected by active sampling method and urine samples were collected from each subject at the end of the work shift. All samples were analyzed using gas chromatography.

RESULTS

The geometric mean ± GSD concentration of isoflurane and sevoflurane in breathing zone air were 1.41 ± 2.27 and 0.005 ± 1.74 ppm, respectively, while in post-shift urine were 2.42 ± 2.86 and 0.006 ± 3.83 µg/l_urine, respectively. A significant positive correlation was found between the urinary and environmental concentration of isoflurane (r ² = 0.724, P < 0.0001). The geometric mean ± GSD values of isoflurane and sevoflurane in ambient air were 2.30 ± 2.43 and 0.004 ± 1.56 ppm, respectively. The isoflurane concentration was different for three studied weeks and significantly increased over time in the ambient air of ORs.

CONCLUSIONS

The occupational exposure of OR personnel to isoflurane and sevoflurane was lower than national recommended exposure limits. The urinary isoflurane could be a good internal dose biomarker for monitoring of occupational isoflurane exposure. Considering the accumulation of anesthetic waste gases in the studied ORs, real-time air monitoring is better to be done at the end of the work shift.

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.

[Comparison of waste anesthetic gases in operating rooms with or without an scavenging system in a Brazilian University Hospital]

BACKGROUND AND OBJECTIVES

Occupational exposure to waste anesthetic gases in operating room (OR) without active scavenging system has been associated with adverse health effects. Thus, this study aimed to compare the trace concentrations of the inhaled anesthetics isoflurane and sevoflurane in OR with and without central scavenging system.

METHOD

Waste concentrations of isoflurane and sevoflurane were measured by infrared analyzer at different locations (near the respiratory area of the assistant nurse and anesthesiologist and near the anesthesia station) and at two times (30 and 120minutes after the start of surgery) in both OR types.

RESULTS

All isoflurane and sevoflurane concentrations in unscavenged OR were higher than the US recommended limit (2 parts per million), regardless of the location and time evaluated. In scavenged OR, the average concentrations of isoflurane were within the limit of exposure, except for the measurements near the anesthesia station, regardless of the measurement times. For sevoflurane, concentrations exceeded the limit value at all measurement locations and at both times.

CONCLUSIONS

The exposure to both anesthetics exceeded the international limit in unscavenged OR. In scavenged OR, the concentrations of sevoflurane, and to a lesser extent those of isoflurane, exceeded the recommended limit value. Thus, the OR scavenging system analyzed in the present study decreased the anesthetic concentrations, although not to the internationally recommended values.

The effects of nitrous oxide on controlled hypotension during low flow anesthesia

BACKGROUND AND OBJECTIVES

We investigated the effect of Nitrous Oxide (N2O) on controlled hypotension in low-flow isoflurane-dexmedetomidine anesthesia in terms of hemodynamics, anesthetic consumption, and costs.

METHODS

We allocated forty patients randomly into two equal groups. We then maintained dexmedetomidine infusion (0.1 μg.kg-1.min-1) for 10 minutes. Next, we continued it until the last 30 minutes of the operation at a dose of 0.7 μg.kg(-1).hour(-1). We administered thiopental (4-6 mg. kg(-1)) and 0.08-0.12 mg.kg(-1) vecuronium bromide at induction for both groups. We used isoflurane (2%) for anesthesia maintenance. Group N received a 50% O2-N2O mixture and Group A received 50% O -air mixture as carrier gas. We started low-flow anesthesia (1 L.min(-1)) after a 10-minute period of initial high flow (4.4 L.min(-1)). We recorded values for blood pressure, heart rate, peripheral O2 saturation, inspiratory isoflurane, expiratory isoflurane, inspiratory O2, expiratory O2, inspiratory N2O, expiratory N2O, inspiratory CO2, CO2 concentration after expiration, Minimum Alveolar Concentration. In addition, we determined the total consumption rate of fentanyl, dexmedetomidine and isoflurane as well as bleeding.

RESULTS

In each group the heart rate decreased after dexmedetomidine loading. After intubation, values were higher for Group A at one, three, five, 10, and 15 minutes. After intubation, the patients reached desired hypotension values at minute five for Group N and at minute 20 for group A. MAC values were higher for Group N at minute one, three, five, 10, and 15 (p < 0.05). FiO2 values were high between minute five and 60 for Group A, while at minute 90 Group N values were higher (p < 0.05). Fi Iso (inspiratuvar isofluran) values were lower in Group N at minute 15 and 30 (p < 0.05).

CONCLUSION

By using dexmedetomidine instead of nitrous oxide in low flow isoflurane anesthesia, we attained desired MAP levels, sufficient anesthesia depth, hemodynamic stability and safe inspiration parameters. Dexmedetomidine infusion with medical air-oxygen as a carrier gas represents an alternative anesthetic technique.

The effects of nitrous oxide on controlled hypotension during low flow anesthesia

BACKGROUND AND OBJECTIVES

We investigated the effect of Nitrous Oxide (N2O) on controlled hypotension in low-flow isoflurane-dexmedetomidine anesthesia in terms of hemodynamics, anesthetic consumption, and costs.

METHODS

We allocated forty patients randomly into two equal groups. We then maintained dexmedetomidine infusion (0.1 μg.kg(-1).min(-1)) for 10 minutes. Next, we continued it until the last 30 minutes of the operation at a dose of 0.7 μg.kg(-1).hour(-1). We administered thiopental (4-6 mg. kg(-1)) and 0.08-0.12 mg.kg(-1) vecuronium bromide at induction for both groups. We used isoflurane (2%) for anesthesia maintenance. Group N received a 50% O2-N2O mixture and Group A received 50% O2-air mixture as carrier gas. We started low-flow anesthesia (1L.min(-1)) after a 10-minute period of initial high flow (4.4L.min(-1)). We recorded values for blood pressure, heart rate, peripheral O2 saturation, inspiratory isoflurane, expiratory isoflurane, inspiratory O2, expiratory O2, inspiratory N2O, expiratory N2O, inspiratory CO2, CO2 concentration after expiration, Minimum Alveolar Concentration. In addition, we determined the total consumption rate of fentanyl, dexmedetomidine and isoflurane as well as bleeding.

RESULTS

In each group the heart rate decreased after dexmedetomidine loading. After intubation, values were higher for Group A at one, three, five, 10, and 15 minutes. After intubation, the patients reached desired hypotension values at minute five for Group N and at minute 20 for group A. MAC values were higher for Group N at minute one, three, five, 10, and 15 (p<0.05). FiO2 values were high between minute five and 60 for Group A, while at minute 90 Group N values were higher (p<0.05). FiIso (inspiratuvar isofluran) values were lower in Group N at minute 15 and 30 (p<0.05).

CONCLUSION

By using dexmedetomidine instead of nitrous oxide in low flow isoflurane anesthesia, we attained desired MAP levels, sufficient anesthesia depth, hemodynamic stability and safe inspiration parameters. Dexmedetomidine infusion with medical air-oxygen as a carrier gas represents an alternative anesthetic technique.

Occupational exposure to isoflurane during anaesthesia induction with standard and scavenging double masks in dogs, pigs and ponies

Induction of anaesthesia using a face mask may cause workplace pollution with anaesthetics. The aim of this study was to compare the effect of the use of a standard versus a scavenging double face mask on isoflurane pollution during induction of anaesthesia in experimental animals: six dogs, 12 pigs and five ponies. Pigs were anaesthetized only once using either mask type randomly ( n = 6). Dogs and ponies were anaesthetized twice, using different mask types for each occasion in a random order with at least 14 days between experiments. The masks were attached to a Bain breathing system (dogs and pigs) or to a circle system (ponies) using a fresh gas flow of 300 or 50 mL/kg/min, respectively, with 5% vaporizer dial setting. Isoflurane concentrations were measured in the anaesthetist's breathing zone using an infrared photoacoustic spectrometer. The peak isoflurane concentrations (pollution) during baseline and induction periods were compared with Wilcoxon test in all species, and values between the mask types were compared with either Wilcoxon (ponies and dogs) or Mann–Whitney tests (pigs) ( P < 0.05). Pollution was higher during induction when compared with baseline regardless of the mask type used but it was only statistically significant in dogs and pigs. Pollution was lower during induction with double versus single masks but it was only significant in pigs. Despite the lack of statistical significance, large and consistent differences were noted in all species, hence using scavenging masks is recommended to reduce isoflurane workplace pollution.

A scavenging double mask to reduce workplace contamination during mask induction of inhalation anesthesia in dogs

Background

Workplace contamination by the use of volatile anesthetic agents should be kept to a minimum if a potential health hazard is to be minimised. Mask induction of animals is a common procedure. The present study investigates the efficiency of a novel scavenging double mask in reducing waste gas concentrations in the breathing zone of the anesthetist performing this procedure.

Methods

Twelve beagle dogs (ASA I) undergoing general anesthesia for a dental procedure were intravenously premedicated with medetomidine and butorphanol (10 μg/kg and 0.2 mg/kg). Anesthesia was induced via a custom-made scavenging mask using isoflurane in oxygen. In six dogs (group S), scavenging from the mask was performed whereas in six other dogs (group NS) the scavenging function was disabled. Isoflurane concentration was continuously measured with photoacoustic spectroscopy at the level of the shoulder of the anesthetist before and during mask induction and additionally during intubation. Statistical analysis was performed with a Student t- test and a Mann-Whitney U test (p < 0.05 for significance).

Results

The mean isoflurane concentration during baseline (premedication) was 1.8 ± 0.8 ppm and 2.3 ± 0.6 ppm in group S and NS respectively. This increased during mask induction to 2.0 ± 0.8 ppm and 11.2 ± 6.0 ppm respectively (p < 0.01). The maximum isoflurane concentration ranged from 0.7 ppm to 2.8 ppm and from from 8.3 ppm to 43.7 ppm in group S and NS respectively.

Conclusion

This double mask can be used to induce inhalation anesthesia in dogs. Scavenging from the mask significantly decreases the amount of waste anaesthetic gas concentrations in the breathing zone of the anesthetist. Therefore, such a system can be recommended whenever induction or maintenance of general anesthesia by mask is considered.

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.

Increase in the use of rebreathing gas flow systems and in the utilization of low fresh gas flows in Finnish anaesthetic practice from 1995 to 2002

BACKGROUND

The use of rebreathing systems together with low fresh gas flows saves anaesthetic gases, reduces the costs of anaesthesia, causes less environmental and ergonomic adverse effects, i.e. less air contamination in the operating room, and has favourable physiological effects. We assessed whether the use of non-rebreathing vs. rebreathing gas flow systems and high vs. lower fresh gas flows has changed during recent years.

METHODS

The use of rebreathing and non-rebreathing systems and the utilization of fresh gas flows were evaluated by sending a questionnaire to the heads of anaesthesia departments at all public health care hospitals in Finland in 1996 and 2003. The data was gathered from the previous years 1995 and 2002, respectively.

RESULTS

The use of rebreathing systems increased from 62% to 83% of all instances of general anaesthesia (P < 0.001). In rebreathing gas flow systems, there was a significant shift from high fresh gas flows (3 l min(-1) and more) towards lower fresh gas flows (between 1 to 2 l min(-1) and even below 1 l min(-1)) (P < 0.001).

CONCLUSIONS

The benefits of low fresh gas flows have now been achieved in most instances of rebreathing system anaesthesia, which was not the case in 1995.

Occupational exposure of midwives to nitrous oxide on delivery suites

AIMS

To compare environmental and biological monitoring of midwives for nitrous oxide in a delivery suite environment.

METHODS

Environmental samples were taken over a period of four hours using passive diffusion tubes. Urine measurements were taken at the start of the shift and after four hours.

RESULTS

Environmental levels exceeded the legal occupational exposure standards for nitrous oxide (100 ppm over an 8 hour time weighted average) in 35 of 46 midwife shifts monitored. There was a high correlation between personal environmental concentrations and biological uptake of nitrous oxide for those midwives with no body burden of nitrous oxide at the start of a shift, but not for others.

CONCLUSIONS

Greater engineering control measures are needed to reduce daily exposure to midwives to below the occupational exposure standard. Further investigation of the toxicokinetics of nitrous oxide is needed.

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).

Surgeon's occupational exposure to nitrous oxide and sevoflurane during pediatric surgery

Health hazards from occupational exposure to trace concentrations of anaesthetic gases cannot be definitively excluded. The aim of the study was to determine the surgeon's occupational exposure to nitrous oxide and sevoflurane during pediatric surgical procedures. Twenty young children (age < 10 years) and five teenagers (age > 10 years) underwent elective abdominal surgery under general inhalational anesthesia. The operating room was equipped with modern air conditioning and waste anesthetic gas scavenger. Levels of both nitrous oxide and sevoflurane were determined in the breathing zone of the surgeon and the anesthesiologist during the operative procedures by means of a direct-reading photoacoustic infrared spectrometer. Both the surgeon and the anesthesiologist were exposed to low concentrations of the inhalational agents used. Exposure to sevoflurane and nitrous oxide was clearly higher during surgery in young children than during operative procedures in teenagers. Nonetheless, the concentrations of these agents were well below the threshold limits of 25 ppm for nitrous oxide and 2 ppm for sevoflurane recommended by the National Institute of Occupational Safety and Health. General anesthesia results in operating room air pollution with inhalational anesthetics. Under modern air conditioning, personnel's occupational exposure is low, and inhalational anesthesia is safe from the standpoint of modern workplace laws and health care regulations. Nonetheless, all efforts must be taken to maintain occupational exposure at this low level.

Occupational exposure to nitrous oxide and desflurane during ear-nose-throat-surgery

PURPOSE

To determine occupational exposure of the anesthesiologist and surgeon to nitrous oxide and desflurane during general anesthesia for ear-nose-throat (ENT) surgery in children and adults.

METHODS

An observational clinical trial was performed in ten children (C) and ten adults (A). Tracheas were intubated, in adults, with cuffed tubes and in children with uncuffed tubes. The operating room was equipped with modern air conditioning and waste anesthetic gas scavengers. Gas samples were obtained during the operative procedure every 90 sec from the breathing zone of subjects. Time-weighted averages (TWA) over the time of exposure were calculated for nitrous oxide and desflurane.

RESULTS

Nitrous oxide TWAs for anesthesiologists were 0.41 +/- 0.23 ppm (A) and 1.20 +/- 0.32 ppm (C, P < 0.0001), and 2.24 +/- 1.93 ppm (A) and 5.30 +/- 0.60 ppm (C, P = 0.0001) for the surgeon who worked close to the patient's airway and thus had higher exposure (P < 0.05 [A], P < 0.0001 [C]). With regard to desflurane, the anesthesiologists' TWAs were 0.02 +/- 0.03 ppm for both adults and children. The surgeon was exposed to 0.21 +/- 0.24 ppm desflurane (A) and 0.30 +/- 0.14 ppm (C, P: n.s.). Although the surgeon's exposure was greater (P < 0.05 [A], P < 0.0001 [C]), the threshold limits of 25 ppm for nitrous oxide and 2 ppm for desflurane recommended by the National Institute of Occupational Safety and Health were not exceeded.

CONCLUSIONS

Under modern air conditioning, occupational exposure to inhalational anesthetics is low, and inhalational anesthesia is safe from the standpoint of modern workplace laws and health-care regulations.

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.