Seeing is Believing: Chasing Sevoflurane Vapor Trails.

PURPOSE: Sevoflurane is an inhalational general anesthetic that has been used recently to treat chronic, painful lesions, reportedly supporting analgesia and wound healing. The potential for repeated exposure to off-gassed sevoflurane vapor, especially outside the air-conditioned operating theatre environment, is of some concern. DESIGN: This paper explores the qualitative and quantitative pathing of off-gassed sevoflurane from a topically applied liquid source. METHODS: Using a small, unventilated test-box (total volume 0.5 m3) with infra-red imaging and gas-analysing, we investigated the spatial distribution of sevoflurane vapor following complete vaporization of a 20 mL liquid sample. Utilizing the infra-red absorption of sevoflurane, it was possible to visualize (as an apparent reduction in temperature) the streaming path of the sevoflurane vapor. Sevoflurane levels (%) in the test-box were measured using an infra-red gas analyzer. FINDINGS: In keeping with its higher density than air, sevoflurane vapor was seen to "waterfall" from the liquid source and accumulate in the bottom of the test-box. Sevoflurane vapor concentration was minimal above the liquid source. When extrapolated to a larger (unventilated) room, we estimate that the sevoflurane concentration would be less than 10 ppm one centimetre above the liquid pool. With vacuum extraction, these levels would be even lower. CONCLUSIONS: Due to sevoflurane's tendency to accumulate on the floor, it is concluded that topical application of liquid sevoflurane posses virtually no risk to off-gas exposure in unventilated spaces.

Nitrous oxide occupational exposure in conscious sedation procedures in endoscopic ambulatories: a pilot retrospective observational study in an Italian hospital.

SUMMARY: Introduction. Nitrous oxide (N2O) is widely used to induce sedation also outside of operating rooms; there is a chance of workplace exposures for the operators engaged in the outpatient use of nitrous oxide. The aim of this research is to assess nitrous oxide exposure in gastroenterology outpatient settings. Methods. We performed an observational study marked by N2O environmental testing in a gastroenterology outpatient care; environmental research was supported by biological monitoring with urinary N2O analysis in exposed operators. The research was conducted both without and using a collective security device (NIKI mask). Results. The study was rolled out in 10 sessions of day shift procedures, totaling 4105 samples. The average N2O concentration in the environment was 27.58 (SD 1.76) and 449.59 (SD 35.29), respectively with and without NIKI Mask; the distribution of gases in the environment under investigation was not homogeneous (Anovatest P=0.001). Biological testing revealed a substantial rise in urinary concentration of 8.97 (p=0.001) between the start and the end of the shift, and the use of the NIKI-mask was effective (p=.003). Discussion. The exposure levels reported exceed the limits of 50 ppm (Italy operating rooms threshold value) as well as the value of 25 ppm (NIOSH threshold-value), indicating a significant issue in the outpatient use of N2O. Technical measures are needed to contain the occupational risk from N2O exposure outside of operating rooms; for the exposure results detected in this research, it is also evident that workers exposed to N2O must be subject to adequate health surveillance accounting for this occupational risk.

Carbon Footprint of General, Regional, and Combined Anesthesia for Total Knee Replacements.

BACKGROUND: Health care itself contributes to climate change. Anesthesia is a "carbon hotspot," yet few data exist to compare anesthetic choices. The authors examined the carbon dioxide equivalent emissions associated with general anesthesia, spinal anesthesia, and combined (general and spinal anesthesia) during a total knee replacement. METHODS: A prospective life cycle assessment of 10 patients in each of three groups undergoing knee replacements was conducted in Melbourne, Australia. The authors collected input data for anesthetic items, gases, and drugs, and electricity for patient warming and anesthetic machine. Sevoflurane or propofol was used for general anesthesia. Life cycle assessment software was used to convert inputs to their carbon footprint (in kilogram carbon dioxide equivalent emissions), with modeled international comparisons. RESULTS: Twenty-nine patients were studied. The carbon dioxide equivalent emissions for general anesthesia were an average 14.9 (95% CI, 9.7 to 22.5) kg carbon dioxide equivalent emissions; spinal anesthesia, 16.9 (95% CI, 13.2 to 20.5) kg carbon dioxide equivalent; and for combined anesthesia, 18.5 (95% CI, 12.5 to 27.3) kg carbon dioxide equivalent. Major sources of carbon dioxide equivalent emissions across all approaches were as follows: electricity for the patient air warmer (average at least 2.5 kg carbon dioxide equivalent [20% total]), single-use items, 3.6 (general anesthesia), 3.4 (spinal), and 4.3 (combined) kg carbon dioxide equivalent emissions, respectively (approximately 25% total). For the general anesthesia and combined groups, sevoflurane contributed an average 4.7 kg carbon dioxide equivalent (35% total) and 3.1 kg carbon dioxide equivalent (19%), respectively. For spinal and combined, washing and sterilizing reusable items contributed 4.5 kg carbon dioxide equivalent (29% total) and 4.1 kg carbon dioxide equivalent (24%) emissions, respectively. Oxygen use was important to the spinal anesthetic carbon footprint (2.8 kg carbon dioxide equivalent, 18%). Modeling showed that intercountry carbon dioxide equivalent emission variability was less than intragroup variability (minimum/maximum). CONCLUSIONS: All anesthetic approaches had similar carbon footprints (desflurane and nitrous oxide were not used for general anesthesia). Rather than spinal being a default low carbon approach, several choices determine the final carbon footprint: using low-flow anesthesia/total intravenous anesthesia, reducing single-use plastics, reducing oxygen flows, and collaborating with engineers to augment energy efficiency/renewable electricity.

Recovery of Sevoflurane Anesthetic Gas Using an Organosilica Membrane in Conjunction with a Scavenging System.

Approximately 95% of the anesthetic gas administered to a patient is exhaled and ultimately released into the atmosphere. Most anesthetic gases have high global warming potential and so this approach adds significantly to the global greenhouse gas footprint. In this work, we develop a feasible means to capture such an anesthetic gas (sevoflurane) before it is released to the hospital scavenging system so that it is retained within the anesthetic circuit. Sevoflurane is retained using a microporous 1,2-bis(triethoxysilyl)ethane (BTESE) membrane prepared by a sol-gel method. The use of a ceramic membrane facilitates sanitization at high temperatures. A rapid thermal processing (RTP) technique is employed to reduce production time and to create a looser organosilica network, resulting in higher gas permeances, compared with the membrane synthesized from conventional thermal processing. The RTP membrane shows a slight decline in gas permeance when used with a dry mixture of CO2/N2/sevoflurane. This permeance falls again under 20% relative humidity feed conditions but the CO2/sevoflurane selectivity increases. The membrane performance shows little variation when the relative humidity is further increased. These promising results demonstrate that this microporous BTESE membrane has great potential for the recovery of sevoflurane in an anesthetic application.

Probabilistic health risk assessment of occupational exposure to isoflurane and sevoflurane in the operating room.

Risk assessment is an important tool in predicting the possible risk to health. It heightens awareness by estimating the probability of adverse health effects in humans who are exposed to chemicals in the course of their work. Therefore, the present work aims to determine the occupational exposure of operating room staff to the volatile anesthetic gases, isoflurane and sevoflurane, and estimates non-cancer risk using the United States Environmental Protection Agency method. Air samples from the breathing zone of staff members were collected using the Occupational Safety and Health Administration Method 103 and analyzed using gas chromatography-mass spectroscopy. The results indicate that the measured concentrations of isoflurane and sevoflurane are below the National Institute of Occupational Safety and Health standard (2 ppm) for technicians and nurses, but not for anesthesiologists and surgeons. Moreover, the estimated non-cancer risk due to isoflurane is above the acceptable value for anesthesiologists (but acceptable for other occupational categories). A sensitivity analysis indicates that exposure time has the most effect on calculated risk (53.4%). Occupational exposure to anesthetic gases may endanger the health of operating room personnel. Therefore, control measures, such as daily testing of anesthetic devices, ensuring the effectiveness of ventilation systems, advanced scavenging methods, and regular training of staff are highly recommended.

New Method of Destroying Waste Anesthetic Gases Using Gas-Phase Photochemistry.

BACKGROUND: The inhalation anesthetics are potent greenhouse gases. To reduce the global environmental impact of the health care sector, technologies are sought to limit the release of waste anesthetic gas into the atmosphere. METHODS: Using a photochemical exhaust gas destruction system, removal efficiencies for nitrous oxide, desflurane, and sevoflurane were measured at various inlet concentrations (25% and 50%; 1.5%, 3.0%, and 6.0%; and 0.5%, 1.0%, and 2.0%, respectively) with flow rates ranging from 0.25 to 2.0 L/min. To evaluate the economic competitiveness of the anesthetic waste gas destruction system, its price per ton of carbon dioxide equivalent was calculated and compared to other greenhouse gas abatement technologies and current market prices. RESULTS: All inhaled anesthetics evaluated demonstrate enhanced removal efficiencies with decreasing flow rates (P < .0001). Depending on the anesthetic and its concentration, the photochemical exhaust gas destruction system exhibits a constant first-order removal rate, k. However, there was not a simple relation between the removal rate k and the species concentration. The costs for removing a ton of carbon dioxide equivalents are <$0.005 for desflurane, <$0.114 for sevoflurane, and <$49 for nitrous oxide. CONCLUSIONS: Based on this prototype study, destroying sevoflurane and desflurane with this photochemical anesthetic waste gas destruction system design is efficient and cost-effective. This is likely also true for other halogenated inhalational anesthetics such as isoflurane. Due to differing chemistry of nitrous oxide, modifications of this prototype photochemical reactor system are necessary to improve its removal efficiency for this gas.

Comparison of 3 Methods to Assess Occupational Sevoflurane Exposure in Abdominal Surgeons: A Single-Center Observational Pilot Study.

BACKGROUND: Studies demonstrated that operating room personnel are exposed to anesthetic gases such as sevoflurane (SEVO). Measuring the gas burden is essential to assess the exposure objectively. Air pollution measurements and the biological monitoring of urinary SEVO and its metabolite hexafluoroisopropanol (HFIP) are possible approaches. Calculating the mass of inhaled SEVO is an alternative, but its predictive power has not been evaluated. We investigated the SEVO burdens of abdominal surgeons and hypothesized that inhaled mass calculations would be better suited than pollution measurements in their breathing zones (25 cm around nose and mouth) to estimate urinary SEVO and HFIP concentrations. The effects of potentially influencing factors were considered. METHODS: SEVO pollution was continuously measured by photoacoustic gas monitoring. Urinary SEVO and HFIP samples, which were collected before and after surgery, were analyzed by a blinded environmental toxicologist using the headspace gas chromatography-mass spectrometry method. The mass of inhaled SEVO was calculated according to the formula mVA = cVA·(Equation is included in full-text article.)·t·ρ VA aer. (mVA: inhaled mass; cVA: volume concentration; (Equation is included in full-text article.): respiratory minute volume; t: exposure time; and ρ VA aer.: gaseous density of SEVO). A linear multilevel mixed model was used for data analysis and comparisons of the different approaches. RESULTS: Eight surgeons performed 22 pancreatic resections. Mean (standard deviation [SD]) SEVO pollution was 0.32 ppm (0.09 ppm). Urinary SEVO concentrations were below the detection limit in all samples, whereas HFIP was detectable in 82% of the preoperative samples in a mean (SD) concentration of 8.53 µg·L (15.53 µg·L; median: 2.11 µg·L, interquartile range [IQR]: 4.58 µg·L) and in all postoperative samples (25.42 µg·L [21.39 µg·L]). The mean (SD) inhaled SEVO mass was 5.67 mg (2.55 mg). The postoperative HFIP concentrations correlated linearly to the SEVO concentrations in the surgeons' breathing zones (ß = 216.89; P < .001) and to the calculated masses of inhaled SEVO (ß = 4.17; P = .018). The surgeon's body mass index (BMI), age, and the frequency of surgeries within the last 24 hours before study entry did not influence the relation between HFIP concentration and air pollution or inhaled mass, respectively. CONCLUSIONS: The biological SEVO burden, expressed as urinary HFIP concentration, can be estimated by monitoring SEVO pollution in the personnel's individual breathing zone. Urinary SEVO was not an appropriate biomarker in this setting.

High concentrations of waste anesthetic gases induce genetic damage and inflammation in physicians exposed for three years: A cross-sectional study.

This cross-sectional study analyzed the impact of occupational waste anesthetic gases on genetic material, oxidative stress, and inflammation status in young physicians exposed to inhalational anesthetics at the end of their medical residency. Concentrations of waste anesthetic gases were measured in the operating rooms to assess anesthetic pollution. The exposed group comprised individuals occupationally exposed to inhalational anesthetics, while the control group comprised individuals without anesthetic exposure. We quantified DNA damage; genetic instability (micronucleus-MN); protein, lipid, and DNA oxidation; antioxidant activities; and proinflammatory cytokine levels. Trace concentrations of anesthetics (isoflurane: 5.3 ± 2.5 ppm, sevoflurane: 9.7 ± 5.9 ppm, and nitrous oxide: 180 ± 150 ppm) were above international recommended thresholds. Basal DNA damage and IL-17A were significantly higher in the exposed group [27 ± 20 a.u. and 20.7(19.1;31.8) pg/mL, respectively] compared to the control group [17 ± 11 a.u. and 19.0(18.9;19.5) pg/mL, respectively], and MN frequency was slightly increased in the exposed physicians (2.3-fold). No significant difference was observed regarding oxidative stress biomarkers. The findings highlight the genetic and inflammatory risks in young physicians exposed to inhalational agents in operating rooms lacking adequate scavenging systems. This potential health hazard can accompany these subjects throughout their professional lives and reinforces the need to reduce ambient air pollution and consequently, occupational exposure.

Real-Time Measurement of Xenon Concentration in a Binary Gas Mixture Using a Modified Ultrasonic Time-of-Flight Anesthesia Gas Flowmeter: A Technical Feasibility Study.

BACKGROUND: Xenon (Xe) is an anesthetic gas licensed for use in some countries. Fractional concentrations (%) of gases in a Xe:oxygen (O2) mixture are typically measured using a thermal conductivity meter and fuel cell, respectively. Speed of sound in such a binary gas mixture is related to fractional concentration, temperature, pressure, and molar masses of the component gases. We therefore performed a study to assess the feasibility of developing a novel single sterilizable device that uses ultrasound time-of-flight to measure both real-time flowmetry and fractional gas concentration of Xe in O2. METHODS: For the purposes of the feasibility study, we adapted an ultrasonic time-of-flight flowmeter from a conventional anesthetic machine to additionally measure real-time fractional concentration of Xe in O2. A total of 5095 readings of Xe % were taken in the range 5%-95%, and compared with simultaneous measurements from the gold standard of a commercially available thermal conductivity Xe analyzer. RESULTS: Ultrasonic measurements of Xe (%) showed agreement with thermal conductivity meter measurements, but there was marked discontinuity in the middle of the measurement range. Bland-Altman analysis (95% confidence interval in parentheses) yielded: mean difference (bias) 3.1% (2.9%-3.2%); lower 95% limit of agreement -4.6% (-4.8% to -4.4%); and upper 95% limit of agreement 10.8% (10.5%-11.0%). CONCLUSIONS: The adapted ultrasonic flowmeter estimated Xe (%), but the level of accuracy is insufficient for clinical use. With further work, it may be possible to develop a device to perform both flowmetry and binary gas concentration measurement to a clinically acceptable degree of accuracy.

Photoacoustic gas monitoring for anesthetic gas pollution measurements and its cross-sensitivity to alcoholic disinfectants.

BACKGROUND: Real-time photoacoustic gas monitoring is used for personnel exposure and environmental monitoring, but its accuracy varies when organic solvents such as alcohol contaminate measurements. This is problematic for anesthetic gas measurements in hospitals, because most disinfectants contain alcohol, which could lead to false-high gas concentrations. We investigated the cross-sensitivities of the photoacoustic gas monitor Innova 1412 (AirTech Instruments, LumaSense, Denmark) against alcohols and alcoholic disinfectants while measuring sevoflurane, desflurane and isoflurane in a laboratory and in hospital during surgery. METHODS: 25 mL ethyl alcohol was distributed on a hotplate. An optical filter for isoflurane was used and the gas monitor measured the 'isoflurane' concentration for five minutes with the measuring probe fixed 30 cm above the hotplate. Then, 5 mL isoflurane was added vaporized via an Anesthetic Conserving Device (Sedana Medical, Uppsala, Sweden). After one-hour measurement, 25 mL isopropyl alcohol, N-propanol, and two alcoholic disinfectants were subsequently added, each in combination with 5 mL isoflurane. The same experiment was in turn performed for sevoflurane and desflurane. The practical impact of the cross-sensitivity was investigated on abdominal surgeons who were exposed intraoperatively to sevoflurane. A new approach to overcome the gas monitor's cross-sensitivity is presented. RESULTS: Cross-sensitivity was observed for all alcohols and its strength characteristic for the tested agent. Simultaneous uses of anesthetic gases and alcohols increased the concentrations and the recovery times significantly, especially while sevoflurane was utilized. Intraoperative measurements revealed mean and maximum sevoflurane concentrations of 0.61 ± 0.26 ppm and 15.27 ± 14.62 ppm. We replaced the cross-sensitivity peaks with the 10th percentile baseline of the anesthetic gas concentration. This reduced mean and maximum concentrations significantly by 37% (p < 0.001) and 86% (p < 0.001), respectively. CONCLUSION: Photoacoustic gas monitoring is useful to detect lowest anesthetic gases concentrations, but cross-sensitivity caused one third falsely high measured mean gas concentration. One possibility to eliminate these peaks is the recovery time-based baseline approach. Caution should be taken while measuring sevoflurane, since marked cross-sensitivity peaks are to be expected.

Evaluation of waste anesthetic gas surveillance program and isoflurane exposures during animal and human surgery.

Prolonged occupational exposure to waste anesthetic gases may have the potential to cause adverse health effects. Workplace exposure surveillance programs are intended to reduce health risk by evaluating exposures to waste anesthetic gases during surgical procedures. Both the personal breathing-zone and area measurements are used to assess occupational exposure in the operating theater. Direct-reading instruments provide real-time measurements and are useful for identifying leaks and evaluating on-the-spot corrective actions. Passive diffusion monitors quantify occupational exposures over time during surgery. The aim of this study was to evaluate a waste anesthetic gas surveillance program to understand occupational exposures and further improve data collection strategy. For this study, 76 survey reports from 2012 through 2014 were retrospectively reviewed to assess occupational exposures to isoflurane in 58 unique procedural rooms operated by the National Institutes of Health. The surveys included industrial hygiene assessments performed during animal and human surgical procedures. The survey reports were evaluated qualitatively and data from these reports was transcribed for quantitative analysis. Variations in sample strategy were observed between surveys and were attributed to ambiguity in the written surveillance program. The study also evaluated the relationship between isoflurane concentrations and sampling method, sampling location, patient type, or scavenging method. Isoflurane exposures were significantly higher among procedures performed on rodents compared to the patients with a large body mass (humans, non-human primates, and swine) (P < 0.05) and in procedures using the charcoal canister exhaust system compared with the central vacuum exhaust system. In addition, individuals performing the surgical procedure experienced elevated occupational exposures measured by both direct-reading instrument and passive diffusion monitors, that is, exposure was significantly higher as measured at the breathing-zone compared with any area within the room (P < 0.05). The study identified several inconsistencies and shortcomings in the surveillance program. Isoflurane concentrations measured during rodent procedures requires further review of work practices and engineering controls. Overall, the findings provide insights to further improve data collection, monitoring, and control of isoflurane exposures.

The Personnel's Sevoflurane Exposure in the Postanesthesia Care Unit Measured by Photoacoustic Gas Monitoring and Hexafluoroisopropanol Biomonitoring.

PURPOSE: Room ventilation in the postanesthesia care unit (PACU) is often poor, although patients exhale anesthetic gases. We investigated the PACU personnel's environmental and biological sevoflurane (SEVO) burden during patient care. DESIGN: Prospective, observational study. METHODS: Air pollution was measured by photoacoustic gas monitoring in the middle of the PACU, above the patient's face, and on the PACU corridor. Urinary SEVO and hexafluoroisopropanol concentrations were determined. FINDINGS: Mean air pollution was 0.34 ± 0.07 ppm in the middle of the PACU, 0.56 ± 0.17 ppm above the patient's face, and 0.47 ± 0.06 ppm on the corridor. Biological preshift exposure levels were 0.13 ± 0.03 mcg/L (SEVO) and 4.72 ± 5.41 mcg/L (hexafluoroisopropanol). Postshift concentrations increased significantly to 0.20 ± 0.06 mcg/L (P = .004) and 42.18 ± 27.82 mcg/L (P < .001). CONCLUSIONS: PACU personnel were environmentally and biologically exposed to SEVO, but exposure levels were minimal according to current recommendations.

High volatile anaesthetic conservation with a digital in-line vaporizer and a reflector.

BACKGROUND: A volatile anaesthetic (VA) reflector can reduce VA consumption (VAC) at the cost of fine control of its delivery and CO2 accumulation. A digital in-line vaporizer and a second CO2 absorber circumvent both of these limitations. We hypothesized that the combination of a VA reflector with an in-line vaporizer would yield substantial VA conservation, independent of fresh gas flow (FGF) in a circle circuit, and provide fine control of inspired VA concentrations. METHOD: Prospective observational study on six Yorkshire pigs. A secondary anaesthetic circuit consisting of a Y-piece with 2 one-way valves, an in-line vaporizer and a CO2 absorber in the inspiratory limb was connected to the patient's side of the VA reflector. The other side was connected to the Y-piece of a circle anaesthetic circuit. In six pigs, an inspired concentration of sevoflurane of 2.5% was maintained by the in-line vaporizer. We measured VAC at FGF of 1, 4 and 10 l/min. RESULTS: With the secondary circuit, VAC was 55% less than with the circle system alone at FGF 1 l/min, and independent of FGF over the range of 1-10 l/min. Insertion of a CO2 absorber in the secondary circuit reduced Pet CO2 by 1.3-2.0 kpa (10-15 mmHg). CONCLUSION: A secondary circuit with reflector and in-line vaporizer provides highly efficient anaesthetic delivery, independent of FGF. A second CO2 absorber was necessary to scavenge the CO2 reflected by the anaesthetic reflector. This secondary circuit may turn any open circuit ventilator into an anaesthetic delivery unit.

Evaluation of a novel waste anaesthetic gas scavenger device for use during recovery from anaesthesia.

Volatile anaesthetic agents are a potential occupational health hazard to theatre and recovery staff. Operating theatres and anaesthetic rooms are required to be equipped with scavenging systems, but recovery units often are not. We compared exhaled, spectrophotometric sevoflurane and desflurane concentrations 15 cm from the mouth ('patient breathing zone') and 91 cm laterally to the patient ('nurse work zone') in 120 patients after tracheal extubation who were consecutively allocated to either ISO-Gard mask oxygen/scavenging or standard oxygen mask, 0 min, 10 min and 20 min after arrival in the theatre recovery unit. Median (IQR [range]) duration of anaesthesia was similar between groups (control 76 (44-119 [15-484]) min vs. study group 90 (64-130 [15-390]) min, p = 0.136). Using the ISO-Gard mask, the 20-min mean patient breathing zone and nurse work zone exhaled anaesthetic levels were ~ 90% and 78% lower than those recorded in the control group, respectively, and were within the recommended 2 ppm maximum environmental exposure limit in the patient breathing zone of 53 out of 60 (88%) and the nurse work zone of all 60 (100%) patients on first measurement in the recovery room (vs. 10 out of 60 (17%) and 40 out of 60 (67%) in the control group). Our study indicates that the ISO-Gard oxygen/scavenging mask reduces the level of exhaled sevoflurane and desflurane below recommended maximum exposure limits near > 85% of extubated patients within ~ 20 s of application in the recovery unit after surgery. We encourage the use of this mask to minimise the occupational exposure of recovery staff to exhaled volatile agents.

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/lurine, 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.

Low anaesthetic waste gas concentrations in postanaesthesia care unit: A prospective observational study.

BACKGROUND: Volatile anaesthetics are a potential hazard during occupational exposure, pregnancy or in individuals with existing disposition to malignant hyperthermia. Anaesthetic waste gas concentration in postanaesthesia care units (PACU) has rarely been investigated. OBJECTIVE(S): The current study aims to assess concentrations of volatile anaesthetics in relation to room size, number of patients and ventilator settings in different PACUs. DESIGN: A prospective observational study. SETTING: Two different PACUs of the Hannover Medical School (Hannover, Germany) were evaluated in this study. The rooms differed in dimensions, patient numbers and room ventilation settings. PATIENTS: During the observation period, sevoflurane anaesthesia was performed in 65 of 140 patients monitored in postanaesthesia unit one and in 42 of 70 patients monitored in postanaesthesia unit two. MAIN OUTCOME MEASURES: Absolute trace gas room concentrations of sevoflurane measured with a compact, closed gas loop high-resolution ion mobility spectrometer. RESULTS: Traces of sevoflurane could be detected in 805 out of 970 samples. Maximum concentrations were 0.96 ±â€Š0.20 ppm in postanaesthesia unit one, 0.82 ±â€Š0.07 ppm in postanaesthesia unit two. Median concentration was 0.12 (0.34) ppm in postanaesthesia unit one and 0.11 (0.28) ppm in postanaesthesia unit two. CONCLUSION: Low trace amounts of sevoflurane were detected in both PACUs equipped with controlled air exchange systems. Occupational exposure limits were not exceeded.

Inhaled anesthetic agent sedation in the ICU and trace gas concentrations: a review.

There is a growing interest in the use of volatile anesthetics for inhalational sedation of adult critically ill patients in the ICU. Its safety and efficacy has been demonstrated in various studies and technical equipment such as the anaesthetic conserving device (AnaConDa™; Sedana Medical, Uppsala, Sweden) or the MIRUS™ system (Pall Medical, Dreieich, Germany) have significantly simplified the application of volatile anesthetics in the ICU. However, the personnel's exposure to waste anesthetic gas during daily work is possibly disadvantageous, because there is still uncertainty about potential health risks. The fact that average threshold limit concentrations for isoflurane, sevoflurane and desflurane either differ significantly between countries or are not even defined at all, leads to raising concerns among ICU staff. In this review, benefits, risks, and technical aspects of inhalational sedation in the ICU are discussed. Further, the potential health effects of occupational long-term low-concentration agent exposure, the staffs' exposure levels in clinical practice, and strategies to minimize the individual gas exposure are reviewed.

Determination of the minimum alveolar concentration (MAC) and cardiopulmonary effects of sevoflurane in sheep.

OBJECTIVE: To determine sevoflurane's minimum alveolar concentration (MACSEVO) and its cardiopulmonary effects in sheep. STUDY DESIGN: Prospective experimental study. ANIMALS: A group of 10 female nonpregnant Sardinian milk sheep. METHODS: Anesthesia was induced in each sheep twice with sevoflurane in oxygen. After a 30 minute equilibration at end-tidal sevoflurane concentration (Fe'Sevo) of 2.8%, an electrical stimulus (5 Hz/1 ms/50 mA) was applied to the right thoracic limb for 1 minute or until gross purposeful movement occurred. The Fe'Sevo was then changed using a 0.2% up-and-down protocol, dependent on whether or not the response was positive, and then noxious stimulation was repeated. The MACSEVO was defined as the mean Fe'Sevo between that allowing purposeful movement and that not. The group of 10 sheep were re-anesthetized and MACSEVO was re-determined. Thereafter, Fe'Sevo was maintained for 15 minutes each at concentrations corresponding to 1.0, 1.3, 1.6, 1.9 and 0.75 MACSEVO multiples, and cardiopulmonary, blood gas, acid-base variables and plasma electrolytes were determined. Also, time to induction of anesthesia, extubation and recovery were recorded. RESULTS: The mean ± standard deviation of the MACSEVO was 2.74 ± 0.38%. Median (interquartile range) time to intubation was 3.13 (2.98-3.33) minutes, time to extubation was 6.85 ± 2.65 minutes and time to recovery was 13.4 ± 5.2 minutes. With increasing Fe'Sevo, arterial blood pressures progressively decreased as did minute ventilation, which in turn caused end-tidal carbon dioxide, arterial partial pressure of carbon dioxide and bicarbonate values to steadily increase without significantly affecting arterial partial pressure of oxygen. CONCLUSIONS AND CLINICAL RELEVANCE: The reported MACSEVO agrees with published data in this and other species. Administration of sevoflurane in sheep caused marked hemodynamic and respiratory depression, but soon after turning off the vaporizer, sheep could be extubated and recovered rapidly and event-free.

A case report of personal exposures to isoflurane during animal anesthesia procedures.

The purpose of this study was to compare personal exposures to isoflurane from participants' breathing zone samples during animal anesthesia procedures by the method of anesthetic gas delivery and the waste anesthetic gas (WAG) control method utilized. WAG control methods included passive scavenging using charcoal canisters, active scavenging using a building vacuum system, and various local exhaust ventilation systems such as laboratory fume hoods and capture hoods. Methods of anesthesia delivery included induction chambers, face masks (also known as nose cones), and intubation. Personal breathing zone samples were collected using 3M 3520 Organic Vapor Diffusion Monitors and submitted to an International Organization for Standardization (ISO) 17025 accredited laboratory for analysis. When using face masks and induction chambers as the method of anesthesia delivery, local exhaust ventilation systems were found to be the best WAG control method to mitigate personal exposures to isoflurane. Personal exposures to isoflurane were well-controlled when animals were intubated, regardless of whether passive scavenging with an adsorptive charcoal canister or active scavenging with a building vacuum system was used. Personal exposures to isoflurane were highest when induction chambers and face masks were used for anesthesia delivery, and passive scavenging with adsorptive charcoal canisters were used as the control method. This study served to identify best practice WAG control methods for research and veterinary procedures that involve isoflurane anesthesia.

Waste anesthetic gas exposure and strategies for solution.

As inhaled anesthetics are widely used, medical staff have inevitably suffered from exposure to anesthetic waste gases (WAGs). Whether chronic exposure to WAGs has an impact on the health of medical staff has long been a common concern, but conclusions are not consistent. Many measures and equipment have been proposed to reduce the concentration of WAGs as far as possible. This review aims to dissect the current exposure to WAGs and its influence on medical staff in the workplace and the environment, and summarize strategies to reduce WAGs.