Occupational exposure to sevoflurane, halothane and nitrous oxide during paediatric anaesthesia. Waste gas exposure during paediatric anaesthesia

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.

High anesthetic (isoflurane) indoor pollution is associated with genetic instability, cytotoxicity, and proliferative alterations in professionals working in a veterinary hospital

This is the first study to monitor anesthetic pollution in veterinary operating rooms (VOR) and assess the toxicological impact of the inhalational anesthetic isoflurane (exposed group) compared to matched volunteers (control group). DNA damage was evaluated in mononuclear cells by the comet assay while genetic instability (including micronucleus-MN), cell proliferation, and cell death markers were assessed by the buccal MN cytome assay. Residual isoflurane concentrations in VOR (air monitoring) lacking the scavenging system were assessed by infrared spectrophotometry; the mean concentration was 11 ppm (≥ 5 times above the international recommended threshold). Comet assay results did not differ between groups; however, both younger exposed professionals (with higher week workload) compared to older individuals exposed for the same period and older professionals with greater time of exposure (years) compared to those in the same age group with fewer years of exposure presented higher DNA damage. The exposed group had a higher frequency of MN, nuclear buds, binucleated cells, karyorrhexis, and karyolysis and a lower frequency of basal cells than the control group. Exposed women were more vulnerable to genetic instability and proliferative index; exposed men presented more cytotoxicity. High WAG exposure has deleterious effects on exposed professionals.

Assessment of anesthetic gases in a central hospital

Introduction:

Adverse health effects related with chronic exposure to waste anesthetic gases remain controversial. Strict threshold values are recommended to minimize possible health risks. The objective of our study was to measure the concentration of waste anesthetic gases in different hospital settings in an 11-year period.

Materials and methods:

Six-monthly assessment of nitrous oxide, sevoflurane, and desflurane was made between 2005 and 2016 in different hospital departments. Trace gas analysis was performed by infrared spectroscopy.

Results:

An anesthetic gas concentration above the upper limit of the threshold value was found in computed tomography/magnetic resonance imaging (CT/MRI) (45.5%), ambulatory operating room (34.5%), and in the burn unit (31.6%). Desflurane assessment was more frequently above the upper limit of threshold value (12.37%).

Discussion:

In the CT/MRI department, the small number of air cycling per hour and the frequent use of a face mask with the associated risk of leakage may explain the results. In burn unit patients inhalatory route is also frequent. Desflurane is widely used for its rapid elimination and rapid recovery, which is compatible with the results. Being odorless, it may be connected to undetected escape.

Conclusion:

The places with more anesthetic agents exposure were the CT/MRI, the ambulatory operating room, and the burn unit. Desflurane was the anesthetic agent more frequently above the upper limit of threshold value. To complement environmental surveillance, it is essential to establish a health surveillance system for professionals exposed to anesthetic agents.

The expert novice - living and working with malignant hyperthermia

Acute care common stem training involves developing competencies within anaesthesia. At this stage of their career, most doctors have little or no anaesthetic experience, and work under direct consultant supervision for the majority of the placement. An emergency medicine trainee with a known diagnosis of malignant hyperthermia undertook a 6-month anaesthetic rotation in a large teaching hospital, adding a unique set of considerations to his training. Having malignant hyperthermia posed a novel challenge to the department, and it was met with an understandable degree of uncertainty and caution. Providing the trainee with a useful and comparable introduction to anaesthesia was of concern, particularly on paediatric lists where there is increased potential for exposure to volatile anaesthetic agents. This report focuses on the trainee's personal reflection of the impact on his experience, as well as looking at how the department responded to this unfamiliar situation, and the learning points to share should a similar scenario be encountered in the future.

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.

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.

The child's behavior during inhalational induction and its impact on the anesthesiologist's sevoflurane exposure

BACKGROUND

Sevoflurane is commonly used for inhalational inductions in children, but the personnel's exposure to it is potentially harmful. Guidance to reduce gas pollution refers mainly to technical aspects, but the impact of the child's behavior has not yet been studied.

AIMS

The purpose of this study was to determine how child behavior, according to the Frankl Behavioral Scale, affects the amount of waste sevoflurane in anesthesiologists' breathing zones.

METHODS

Sixty-eight children aged 36-96 months undergoing elective ENT surgery were recruited for this prospective, observational investigation. After oral midazolam premedication (0.5 mg/kg body weight), patients obtained sevoflurane using a facemask with an inspiratory concentration of 8 Vol.% in 100% oxygen (flow 10 L/min). Ventilation was manually supported and a venous catheter was placed. The inspiratory sevoflurane concentration was reduced, and remifentanil and propofol were administered before the facemask was removed and a cuffed tracheal tube inserted. The child's behavior toward the operating room personnel during induction was evaluated by the anesthesiologist (Frankl Behavioral Scale: 1-2 = negative behavior, 3-4 = positive behavior). During induction mean (c¯mean) and maximum (c¯max), sevoflurane concentrations were determined in the anesthesiologist's breathing zone by continuous photoacoustic gas monitoring.

RESULTS

Mean and maximum sevoflurane concentrations were c¯mean = 4.38 ± 4.02 p.p.m and c¯max = 70.06 ± 61.08 p.p.m in patients with positive behaviors and sufficient premedications and c¯mean = 12.63 ± 8.66 p.p.m and c¯max = 242.86 ± 139.91 p.p.m in children with negative behaviors and insufficient premedications (c¯mean: P < .001; c¯max: P < .001).

CONCLUSION

Negative behavior was accompanied by significantly higher mean and maximum sevoflurane concentrations in the anesthesiologist's breathing zone compared with children with positive attitudes. Consequently, the status of premedication influences the amount of sevoflurane pollution in the air of operating rooms.

Nitrous Oxide Exposure of Health Care Personnel in the Operating Rooms and Intensive Care Units in Hospitals in Macedonia

AIM:

To determine average personal exposure to nitrous oxide for anaesthesiologists and nurses working in operating rooms (ORs) and intensive care units (ICU) in Clinical Hospital in Shtip, ENT University Clinic in Skopje and General Hospital in Kochani.

METHODS:

To determine TWA exposure nitrous oxide concentration was continuously measured over 8 hours shift within breathing zone of the subjects involved, using the handheld electrochemical instrument with data logging option. Results obtained were statistically processed.

RESULTS:

Highest TWA exposures (well above RELs) were found for nurses and anaesthesiologists in ORs in CH – Shtip, because of high workload in substandard conditions. TWA exposures in CH – Kochani were found to be significantly lower although in substandard conditions, mostly due to lower workload. TWA exposures found in ORs in ENT UC – Skopje is within RELs due to good work practices and proper ORs equipment.

CONCLUSIONS:

Study indicated significant exposure of personal working in substandard ORs in CH – Shtip. Applying proper work practices and maintain control equipment (general ventilation and scavenging systems) in operation, could provide for safe work environment.

Evaluation and control of isoflurane during experimental dental procedures on rodents

The purpose of this study was to assess exposures to isoflurane to employees performing an experimental dental procedure on rodents. Isoflurane was used as an anesthetic for rodents during injections and placement of dental apparatus into the mouth. We collected eight full-shift samples using passive badges over a three-week period. The procedure was performed once a week for approximately 45 min each day. Results showed that employees were being exposed to isoflurane above the National Institute for Occupational Safety and Health recommended exposure level for halogenated anesthetic gases of two parts per million. The employer installed a ventilation system in the procedure room after the initial sampling and results. We collected 12 full-shift samples after the ventilation system was in place. Results showed an approximate 86% decrease in isoflurane concentration.

Occupational Chronic Sevoflurane Exposure in the Everyday Reality of the Anesthesia Workplace

BACKGROUND

Although sevoflurane is one of the most commonly used volatile anesthetics in clinical practice, anesthesiologists are hardly aware of their individual occupational chronic sevoflurane exposure. Therefore, we studied sevoflurane concentrations in the anesthesiologists' breathing zones, depending on the kind of induction for general anesthesia, the used airway device, and the type of airflow system in the operating room. Furthermore, sevoflurane baselines and typical peaks during general anesthesia were determined.

METHODS

Measurements were performed with the LumaSense Photoacoustic Gas Monitor. As we detected the gas monitor's cross-sensitivity reactions between sevoflurane and disinfectants, regression lines for customarily used disinfectants during surgery (Cutasept®, Octeniderm®) and their alcoholic components were initially analyzed. Hospital sevoflurane concentrations were thereafter measured during elective surgery in 119 patients. The amount of inhaled sevoflurane by anesthesiologists was estimated according to mVA = cVA × V × t × ρVA aer.

RESULTS

Induction of general anesthesia stopped after tracheal intubation with the patient's expiratory sevoflurane concentration of 1.5%. Thereby, inhalational inductions (INH) caused higher sevoflurane concentrations than IV inductions (mean [SD]: (Equation is included in full-text article.)[ppm] INH 2.43 ± 1.91 versus IV 0.62 ± 0.33, P < 0.001; mVA [mg] INH 1.95 ± 1.54 versus IV 0.30 ± 0.22, P < 0.001). The use of laryngeal mask airway (LMA™) led to generally higher sevoflurane concentrations in the anesthesiologists' breathing zones than tracheal tubes ((Equation is included in full-text article.)[ppm] tube 0.37 ± 0.16 versus LMA™ 0.79 ± 0.53, P = 0.009; (Equation is included in full-text article.)[ppm] tube 1.91 ± 0.91 versus LMA™ 2.91 ± 1.81, P = 0.057; mVA [mg] tube 1.47 ± 0.64 versus LMA™ 2.73 ± 1.81, P = 0.019). Sevoflurane concentrations were trended higher during surgery in operating rooms with turbulent flow (TF) air-conditioning systems compared with laminar flow (LF) air-conditioning systems ((Equation is included in full-text article.)[ppm] TF 0.29 ± 0.12 versus LF 0.13 ± 0.06, P = 0.012; mVA [mg/h] TF 1.16 ± 0.50 versus LF 0.51 ± 0.25, P = 0.007).

CONCLUSIONS

Anesthesiologists are chronically exposed to trace concentrations of sevoflurane during work. Inhalational inductions, LMA™, and TF air-conditioning systems in particular are associated with higher sevoflurane exposure. However, the amount of inhaled sevoflurane per day was lower than expected, perhaps because concentrations in previous measurements could be overestimated (10%-15%) because of the cross-sensitivity reaction.

Determination of sevoflurane and isopropyl alcohol in exhaled breath by thermal desorption gas chromatography-mass spectrometry for exposure assessment of hospital staff

Volatile anaesthetics and disinfection chemicals pose ubiquitous inhalation and dermal exposure risks in hospital and clinic environments. This work demonstrates specific non-invasive breath biomonitoring methodology for assessing staff exposures to sevoflurane (SEV) anaesthetic, documenting its metabolite hexafluoroisopropanol (HFIP) and measuring exposures to isopropanol (IPA) dermal disinfection fluid. Methods are based on breath sample collection in Nalophan bags, followed by an aliquot transfer to adsorption tube, and subsequent analysis by thermal desorption gas chromatography-mass spectrometry (TD-GC-MS). Ambient levels of IPA were also monitored. These methods could be generalized to other common volatile chemicals found in medical environments. Calibration curves were linear (r(2)=0.999) in the investigated ranges: 0.01-1000 ppbv for SEV, 0.02-1700 ppbv for IPA, and 0.001-0.1 ppbv for HFIP. The instrumental detection limit was 10 pptv for IPA and 5 pptv for SEV, both estimated by extracted ion-TIC chromatograms, whereas the HFIP minimum detectable concentration was 0.5 pptv as estimated in SIM acquisition mode. The methods were applied to hospital staff working in operating rooms and clinics for blood draws. SEV and HFIP were present in all subjects at concentrations in the range of 0.7-18, and 0.002-0.024 ppbv for SEV and HFIP respectively. Correlation between IPA ambient air and breath concentration confirmed the inhalation pathway of exposure (r=0.95, p<0.001) and breath-borne IPA was measured as high as 1500 ppbv. The methodology is easy to implement and valuable for screening exposures to common hospital chemicals. Although the overall exposures documented were generally below levels of health concern in this limited study, outliers were observed that indicate potential for acute exposures.

Quantitative chemical analysis of surgical smoke generated during laparoscopic surgery with a vessel-sealing device

BACKGROUND

Exposure to surgical smoke in the operation room has been a long-standing concern. Smoke generated by the interaction between lasers or electrocautery devices with biological tissue contains several toxic and carcinogenic substances, but only a few studies so far have provided quantitative data necessary for risk assessment.

METHODS

With laser and Fourier-transform infrared spectroscopy, we investigated the chemical composition of smoke produced with a vessel-sealing device in an anoxic environment during laparoscopic surgery.

RESULTS

Harmless concentrations of methane (<34 ppm), ethane (<2 ppm), and ethylene (<10 ppm) were detected. Traces of carbon monoxide (<3.2 ppm) and of the anesthetic sevoflurane (<450 ppm) were also found. CONCLUSIONS. Gas leaking or gas being released from the pneumoperitoneum could therefore increase pollution by waste anesthetic gas in the operating room. Most toxic compounds found in earlier studies remained undetected. Adverse health effects for operating room personnel due to some of those substances (e.g., toluene, styrene, xylene) can be excluded, assuming no significant losses or changes in the chemical composition of the samples occurred between our sampling and measurements.

Field application of SPME as a novel tool for occupational exposure assessment with inhalational anesthetics

Occupational exposure to inhalational anesthetics occurs routinely in operating rooms. It could induce serious health hazards and diseases. This exposure assessment is a crucial step in determining risks. In this study, a pen-shaped holder for solid-phase microextraction (SPME) sampler was successfully applied as a time-weighted average sampling tool for workshift exposure assessment of operation room staff to halothane. It proved to be very convenient for use in occupational environments such as operation rooms. Samples were analyzed by a gas chromatography-mass spectrometry. The validity of the SPME method was checked in real-world conditions with Occupational Safety and Health Administration (OSHA) 103 standard method for the determination of inhalational anesthetics. A good agreement between OSHA 103 and SPME methods was obtained and results demonstrated no statistically significant differences in anesthetic concentrations determined by the two analytical methods (p ≥ 0.05). It is concluded that SPME in retracted mode could successfully be applied in occupational exposure assessment purposes.

Assessment of genotoxicity risk in operation room personnel by the alkaline comet assay

This study was conducted to evaluate the possible genotoxic effects of waste anesthetic gases. Comet assay was performed on peripheral blood lymphocytes of 60 volunteers: 20 healthy unexposed office workers and 40 operation room (OR) personnel at Tanta University Hospital (Egypt). The exposed personnel were anesthetists (6 females and 7 males), surgeons (10 males), nurses (9 females), and technicians (8 males). The study revealed significantly increased comet parameters (mean comet tail length and mean percentage of DNA in the tail) in peripheral blood lymphocytes of OR personnel in comparison with control individuals. The maximum DNA damage was observed in anesthesia technicians, whereas the nurses showed the least DNA damage. Furthermore, significant difference was observed between smoker and nonsmokerOR personnel in relation to mean comet tail length. However, no significant difference was seen due to age, gender, or duration of exposure. Also, significant increase in mean percentage of tail DNA was observed in smoker individuals of both exposed and control groups. As a conclusion, this study points to the risk of DNA damage in personnel who are exposed to waste anesthetic gases.

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.

DNA damage, glutathione, and total antioxidant capacity in anesthesia nurses

The possibilities of a potential mutagenic/carcinogenic action of waste anesthetic gases in occupationally exposed anesthesia personnel have been previously reported in several studies. The aim of this study was to assess the DNA damage, reduced glutathione (GSH), and total antioxidant capacity (TAC) in anesthesia nurses. DNA damage was determined with comet assay, GSH levels were measured spectrophotometrically, and TAC was determined by using Randox kit. Anesthesia nurses (n = 40) showed increased DNA damage in terms of mean percentage of the total DNA in the comet tail compared to controls (n = 40) (p < .001). Mean TAC and GSH levels of the anesthesia nurses were significantly lower than that of the controls (p < .001, p < .05, respectively). The results of this study indicate that occupational exposure to anesthetic gases induce DNA damage, which may lead to changes in TAC and GSH levels.

Personnel breathing zone sevoflurane concentration adherence to occupational exposure limits in conjunction with filling of vaporisers

BACKGROUND

Work place pollution during filling of anaesthetic vaporisers has been a matter of concern. We studied personnel breathing zone ambient air sevoflurane concentrations during filling of sevoflurane with three different filling systems: Quik-Fil™ for Abbott and Dräger Fill™ resp. Easy-Fil™ adapters for Baxter sevoflurane bottles, referred to as 'Abbott and Baxter filling systems'.

METHOD

Sequential filling of three vaporisers was performed for a 15-min period, once with each of Abbott and Baxter filling systems, by four nurses. Ambient-air sevoflurane p.p.m. concentration in the breathing zone was continuously measured using a Miran 1a device during filling, and the mean 15 min sevoflurane concentration was calculated.

RESULTS

All eight measured (4 × 2 sequences) 15-min mean breathing zone sevoflurane concentrations covering filling of three vaporisers were well below the recommended short-term value (STV) provided by the Swedish Work Environment Authority (STV 20 p.p.m.).

CONCLUSION

The breathing zone sevoflurane concentration during filling of sevoflurane with Baxter or Abbott filling systems, in an ordinary operating theatre, was found to be reassuringly below the Swedish recommended STV (20 p.p.m. average for a 15-min period).

Sevoflurane inside and outside the operating room

BACKGROUND

Sevoflurane is often presented as a near-perfect anaesthetic. After 10 years in the operating room, new uses are emerging outside.

OBJECTIVE

To remind readers of the principal characteristics of sevoflurane, to affirm its usefulness for day-case anaesthesia and to consider the recent new uses.

METHODS

The discussion of the physical properties, pharmacokinetics, metabolism, mechanisms of action and clinical effects is based on classic, essential papers. Recent literature concerning emerging utilizations of sevoflurane was analysed.

RESULTS

Sevoflurane presents many benefits with minimum inconvenience. It allows rapid inhalation induction, maintenance and rapid recovery. It has little toxicity and its haemodynamic and respiratory depressive effects are moderate and well tolerated. It is already widely use for sedation for magnetic resonance imaging in children. Its use in paediatric or adult intensive care could improve the management of pain and sedation.

Impaired vitamin B12 metabolic status in healthcare workers occupationally exposed to nitrous oxide

BACKGROUND

Previous studies demonstrated inactivation of vitamin B12 by nitrous oxide (N(2)O). The intraoperative exposure to N(2)O was shown to induce megaloblastic anaemia and myelopathy in subjects with subclinical vitamin B12 deficiency. In contrast, no data concerning the influence of occupational exposure to N(2)O on vitamin B12 metabolic status are available to date. In the present study, the vitamin B12 status in operating theatre personnel was assessed in relation to the extent of exposure.

METHODS

Ninety-five operating theatre nurses with the history of exposure to N(2)O and 90 unexposed counterparts were examined. Vitamin B12 and folic acid were measured by immunoassay. Total homocysteine (tHcy), an indicator of impaired vitamin B12 metabolism, was determined by high performance liquid chromatography. N(2)O concentration was monitored by adsorption gas chromatography and mass spectrometry.

RESULTS

No significant differences were found between both groups with respect to haematological parameters and folic acid. However, subjects exposed to N(2)O presented with lower vitamin B12 [372.8 (12.1) vs 436.8 (13.2) pmol litre(-1), P<0.001] and higher tHcy [11.2 (0.5) vs 8.9 (0.5) micromol litre(-1), P=0.006]. The changes in vitamin B12 status were aggravated in subjects exposed to N(2)O in concentrations substantially exceeding occupational exposure limit (180 mg m(-3)) [vitamin B12: 341.9 (17.7) vs 436.8 (13.2) pmol litre(-1), P=0.006; tHcy: 12.9 (0.7) vs 8.9 (0.5) micromol litre(-1), P=0.047].

CONCLUSIONS

Exposure to N(2)O in healthcare workers is associated with alterations of vitamin B12 metabolic status, the extent of which depends on the level of exposure.

Occupational exposure to nitrous oxide – The role of scavenging and ventilation systems in reducing the exposure level in operating rooms

OBJECTIVES

The aim of this study was to assess the level of occupational exposure to nitrous oxide (N(2)O) in operating rooms (ORs), as related to different ventilation and scavenging systems used to remove waste anaesthetic gases from the work environment.

METHODS

The monitoring of N(2)O in the air covered 35 ORs in 10 hospitals equipped with different systems for ventilation and anaesthetic scavenging. The examined systems included: natural ventilation with supplementary fresh air provided by a pressure ventilation system (up to 6 air changes/h); pressure and exhaust ventilation systems equipped with ventilation units supplying fresh air to and discharging contaminated air outside the working area (more than 10 air changes/h); complete air-conditioning system with laminar air flow (more than 15 air changes/h). The measurements were carried out during surgical procedures (general anaesthesia induced intravenously and maintained with inhaled N(2)O and sevofluran delivered through cuffed endotracheal tubes) with connected or disconnected air scavenging. Air was collected from the breathing zone of operating personnel continuously through the whole time of anaesthesia to Tedlar((R)) bags, and N(2)O concentrations in air samples were analyzed by adsorption gas chromatography/mass spectrometry.

RESULTS

N(2)O levels in excess of the occupational exposure limit (OEL) value of 180mg/m(3) were registered in all ORs equipped with ventilation systems alone. The OEL value was exceeded several times in rooms with natural ventilation plus supplementary pressure ventilations and twice or less in those with pressure/exhaust ventilation systems or air conditioning. N(2)O levels below or within the OEL value were observed in rooms where the system of air conditioning or pressure/exhaust ventilation was combined with scavenging systems. Systems combining natural/pressure ventilation with scavenging were inadequate to maintain N(2)O concentration below the OEL value.

CONCLUSION

Air conditioning and an efficient pressure/exhaust ventilation (above 12 air exchanges/h) together with efficient active scavenging systems are sufficient to sustain N(2)O exposure in ORs at levels below or within the OEL value of 180mg/m(3).

The use of nitrous oxide in paediatric anaesthetic practice in the United Kingdom: a questionnaire survey

Nitrous oxide pollution is common in paediatric anaesthetic practice. A questionnaire was sent to all UK members of the Association of Paediatric Anaesthetists requesting details of three areas of their paediatric practice relating to nitrous oxide: attitudes to its use; current usage; and availability of alternatives. Replies were received from 296 (68%) consultants. Of these, 169 (57%) stated that their use of nitrous oxide had decreased over the last 5 years. One hundred and fifty-eight (54%) considered theatre pollution a problem in paediatric anaesthesia. One hundred and sixty-nine (57%) reported that in normal circumstances potential deleterious effects on patients influenced their use of nitrous oxide, whilst only 70 (24%) felt potential effects on staff influenced usage. Fifty-five (18%) felt there should be some restriction in the availability of nitrous oxide.

Do we need inhaled anaesthetics to blunt arousal, haemodynamic responses to intubation after i.v. induction with propofol, remifentanil, rocuronium?

BACKGROUND

The aim of this study was to determine whether, after propofol, rocuronium and remifentanil rapid sequence induction, inhaled anaesthetic agents should be started before intubation to minimize autonomic and arousal response during intubation.

METHODS

One hundred ASA I and II patients were randomized to receive 1 MAC of desflurane or sevoflurane during manual ventilation or not. Anaesthesia was induced with an effect-site-controlled infusion of remifentanil at 2 ng ml(-1) for 3 min. Patients then received propofol to induce loss of consciousness (LOC). Rocuronium (0.6 mg kg(-1)) was given at LOC and the trachea was intubated after 90 s of manual breathing support (=baseline) with or without inhaled anaesthetics. Vital signs and bispectral index (BIS) were recorded until 10 min post-intubation to detect autonomic and arousal response.

RESULTS

A significant increase in BIS value after intubation was seen in all groups. The increases were mild, even in those not receiving pre-intubation inhaled anaesthetics. However, in contrast to sevoflurane, desflurane appeared to partially blunt the arousal response. Heart rate, systolic and diastolic pressure increase similarly in all groups.

CONCLUSIONS

Desflurane and sevoflurane were unable to blunt the arousal reflex completely, as measured by BIS, although the reflex was significantly less when desflurane was used. Rapid sequence induction with remifentanil, propofol and rocuronium and without inhaled anaesthetics before intubation can be done without dangerous haemodynamic and arousal responses at intubation after 90 s.

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.

Sevoflurane: an ideal agent for adult day-case anesthesia?

Sevoflurane has several properties which make it potentially useful as a day case anaesthetic. Following induction of anaesthesia with propofol, awakening from sevoflurane is faster compared to isoflurane, faster or similar compared to propofol and comparable (in the majority of studies) to desflurane. Subsequent recovery and discharge is generally similar following all agents. Sevoflurane may also be used to induce anaesthesia, which is generally well-received and causes less hypotension and apnoea compared to propofol. When used as a maintenance anaesthetic, the incidence of postoperative nausea and vomiting after sevoflurane is comparable to other inhaled anaesthetics, but this complication appears more common after inhaled inductions. The tolerability and low solubility of sevoflurane facilitate titration of anaesthesia and may reduce the need for opioid analgesia, which in turn may limit the occurrence of nausea and vomiting.

A survey of obstetric complications and pregnancy outcomes in paediatric and nonpaediatric anaesthesiologists

BACKGROUND

Obstetric complications such as spontaneous abortion, preterm labour, preterm delivery, low birth weight and congenital anomalies may be associated with exposure to anaesthetic gases. We hypothesized that female anaesthesiologists practicing primarily paediatric anaesthesia, with increased exposure to trace anaesthetic agents, experience a greater prevalence of obstetric complications than female anaesthesiologists performing primarily adult anaesthesia.

METHODS

Questionnaires were sent to all female Society for Pediatric Anesthesia (SPA) members and to an equal number of randomly selected female American Society of Anesthesiologists (ASA) members. Subjects were asked to answer questions regarding their pregnancy outcomes, work history and personal habits. Parametric data were analysed by unpaired t-tests. Nonparametric data were analysed by chi-square, Fisher's exact test and Mann-Whitney U-test as appropriate.

RESULTS

Paediatric anaesthesiologists were defined as those having >75% paediatric practice. Paediatric anaesthesiologists were older and had greater operating room exposure during their pregnancies than nonpaediatric anaesthesiologists. There was a significantly higher prevalence of spontaneous abortion among paediatric anaesthesiologists than nonpaediatric anaesthesiologists. In an exploratory analysis, the following factors were found to be significantly associated with the development of spontaneous abortion: age >35 years, gravida >1, exercise during pregnancy, percentage of inhalational anaesthetics >75% and paediatric anaesthesia practice >75%. Independent risk factors for spontaneous abortion among anaesthesiologists included exercise (>1 time/week) and age.

CONCLUSION

Our results suggest a higher prevalence of spontaneous abortion in anaesthesiologists whose practice is >75% paediatrics.

Environmental monitoring of sevoflurane and nitrous oxide using the cuffed oropharyngeal airway

We compared exposure to sevoflurane (SEV) and nitrous oxide (N(2)O) during ventilation using the cuffed oropharyngeal airway (COPA) with waste gas exposure using a conventional face mask (FM) without any additional airways or face straps and with the laryngeal mask airway (LMA). Trace concentrations of SEV and N(2)O were assessed by using a direct reading spectrometer during 33 surgical procedures under general anesthesia. Measurements were made at the patients' mouths and in the anesthesiologists' breathing zones. Mean +/- SD concentrations of SEV and N(2)O measured at the patients' mouths were comparable in the COPA (SEV, 8.1 +/- 12.2 ppm; N(2)O, 213.3 +/- 289.2 ppm) and LMA (SEV, 18.5 +/- 25.8 ppm; N(2)O, 283.4 +/- 361.0 ppm) groups but differed significantly from the FM group (SEV, 46.5 +/- 19.6 ppm; N(2)O, 750.7 +/- 308.3 ppm). These values resulted in a comparable contamination of the anesthesiologists' breathing zones (SEV, 0.5 +/- 0.2 ppm; N(2)O, 5.7 +/- 4.8 ppm) for the COPA group, compared with the LMA group (SEV, 1.0 +/- 0.9 ppm; N(2)O, 12.2 +/- 14.3 ppm). This differed significantly from the FM group (SEV, 2.2 +/- 0.9 ppm; N(2)O, 37.5 +/- 14.3 ppm). We conclude that the use of the COPA during short surgical interventions has an occupational safety comparable to that of the LMA and that both resulted in less contamination through waste anesthetic gases. Therefore, the COPA may be a valuable alternative to the conventional FM.

IMPLICATIONS

In this study, we have shown that the occupational exposure to waste anesthetic gases is comparable when using the cuffed oropharyngeal airway (COPA) and the laryngeal mask airway and is increased when using the face mask. Therefore, the COPA may be a valuable alternative to the conventional face mask during short surgical procedures.

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.

Online monitoring of air quality at the postanesthetic care unit by proton-transfer-reaction mass spectrometry

The subthreshold exposure to trace anesthetic gases is not associated with considerable risk of adverse health effects. Online control of ambient air exchange at the postoperative workplace may help in supervising air quality and lead to cost reduction. A proton-transfer-reaction mass spectrometer system was used for online monitoring of volatile organic compounds, especially anesthetic gases. The mean exposure to sevoflurane and isoflurane at the urological postanesthesia care unit (PACU) was 15.9 and 9.5 parts per billion, respectively. Sevoflurane and isoflurane concentrations at the urological PACU showed a patient turnover-dependent burden during our investigation period. Because modern PACUs have a high ventilation capacity, the 24-h occupational burden by anesthetic gases at the PACU is relatively low. Monitoring and controlling of ambient air by automatic built-in alarm systems would be useful for quality control of the postoperative workplace. Moreover, energy costs of ventilation systems could be reduced by coupling ventilation capacity to the effective exposure.

Waste gas exposure to sevoflurane and nitrous oxide during anaesthesia using the oesophageal-tracheal Combitube small adult

Exposure to sevoflurane (SEV) and nitrous oxide during ventilation using a Combitube (37Fr) small adult (SA) was compared with waste gas exposure using conventional endotracheal tubes. Trace concentrations of SEV and nitrous oxide were assessed using a direct reading spectrometer during 40 gynaecological laparoscopic procedures under general anaesthesia. Measurements were made at the patients' mouth and in the anaesthetists' breathing zone. Mean (SD) concentrations of SEV and nitrous oxide measured at the patients' mouth were comparable in the Combitube SA (SEV 0.6 (0.2) p.p.m.; nitrous oxide 9.7 (8.5) p.p.m.) and endotracheal tube group (SEV 1.2 (0.8) p.p.m.; nitrous oxide 17.2 (10.6) p.p.m.). These values caused comparable contamination of the anaesthetists' breathing zone (SEV 0.6 (0.2) p.p.m. and nitrous oxide 4.3 (3.7) p.p.m. for the Combitube SA group, compared with SEV 0.5 (0.2) p.p.m. and nitrous oxide 4.1 (1.8) p.p.m. for the endotracheal tube group). We conclude that the use of the Combitube SA during positive pressure ventilation is not necessarily associated with increased waste gas exposure, especially when air conditioning and scavenging devices are available.

The SiBI connector: a new medical device to facilitate preoxygenation and reduce waste anesthetic gases during inhaled induction with sevoflurane

IMPLICATIONS

The SiBI connector is a new medical device used for vital capacity inhaled induction with sevoflurane. It allows efficient preoxygenation of patients and reduces waste anesthetic gases in the operation room during induction.

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.

Genetic damage in operating room personnel exposed to isoflurane and nitrous oxide

OBJECTIVES

To evaluate genetic damage as the frequency of sister chromatid exchanges and micronuclei in lymphocytes of peripheral blood of operating room personnel exposed to waste anaesthetic gases.

METHODS

Occupational exposure was measured with a direct reading instrument. Venous blood samples were drawn from 10 non-smokers working in the operating room and 10 non-smoking controls (matched by age, sex, and smoking habits). Lymphocytes were cultured separately over 72 hours for each assay with standard protocols. At the end of the culture time, the cells were harvested, stained, and coded for blind scoring. The exchanges of DNA material were evaluated by counting the number of sister chromatid exchanges in 30 metaphases per probe or by counting the frequency of micronuclei in 2000 binucleated cells. Also, the mitotic and proliferative indices were measured.

RESULTS

The operating room personnel at the hospital were exposed to an 8 hour time weighted average of 12.8 ppm nitrous oxide and 5.3 ppm isoflurane. The mean (SD) frequency of sister chromatid exchanges was significantly higher (10.2 (1.9) v 7.4 (2.4)) in exposed workers than controls (p = 0.036) the proportion of micronuclei (micronuclei/500 binucleated cells) was also higher (8.7 (2.9) v 6.8 (2.5)), but was not significant (p = 0.10).

CONCLUSION

Exposure even to trace concentrations of waste anaesthetic gases may cause dose-dependent genetic damage. Concerning the micronuclei test, no clastogenic potential could be detected after average chronic exposure to waste anaesthetic gas. However, an increased frequency of sister chromatid exchanges in human lymphocytes could be detected. Although the measured differences were low, they were comparable with smoking 11-20 cigarettes a day. Due to these findings, the increased proportion of micronuclei and rates of sister chromatid exchanges may be relevant long term and need further investigation.

Exposure to sevoflurane and nitrous oxide during four different methods of anesthetic induction

The National Institute for Occupational Safety and Health-recommended exposure levels for nitrous oxide exposure are 25 ppm as a time-weighted average over the time of exposure. The exposure limit for halogenated anesthetics (without concomitant nitrous oxide exposure) is 2 ppm. Inhaled sevoflurane provides an alternative to i.v. induction of anesthesia. However, the inadvertent release of anesthetic gases into the room is likely to be greater than that with induction involving i.v. anesthetics. We therefore evaluated anesthesiologist exposure during four different induction techniques. Eighty patients were assigned to one of the induction groups to receive: 1) sevoflurane and nitrous oxide from a rebreathing bag, 2) sevoflurane and nitrous oxide from a circle circuit, 3) propofol 3 mg/kg, and 4) thiopental sodium 5 mg/kg. Anesthesia was maintained with sevoflurane and nitrous oxide via a laryngeal mask. Trace concentrations were measured directly from the breathing zone of the anesthesiologist. During induction, peak concentrations of sevoflurane and nitrous oxide with the two i.v. methods rarely exceeded 2 ppm sevoflurane and 50 ppm nitrous oxide. Concentrations during the two inhalation methods were generally <20 ppm sevoflurane and 100 ppm nitrous oxide. During maintenance, median values were near 2 ppm sevoflurane and 50 ppm nitrous oxide in all groups. Sevoflurane concentrations during inhaled induction frequently exceeded the National Institute for Occupational Safety and Health-recommended exposure ceiling of 2 ppm but mostly remained <20 ppm. Exposure during the maintenance phase of anesthesia also frequently exceeded the 2-ppm ceiling. We conclude that operating room anesthetic vapor concentrations are increased during inhaled inductions and remain increased with laryngeal mask ventilation.

IMPLICATIONS

We compared waste gas concentrations to sevoflurane and nitrous oxide during four different induction methods. During inhaled induction with a rebreathing bag or a circle circuit system, waste gas concentrations frequently exceed National Institute for Occupational Safety and Health limits of 2 ppm sevoflurane and 50 ppm nitrous oxide. Therefore, we recommend that people at risk (e.g., women of child-bearing age) should pay great attention when using this technique.