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

Peri-anesthetic Environmental and Occupational Exposure to Desflurane Waste Anesthetic Gas in a Large Animal Veterinary Hospital

OBJECTIVES

The goals were to determine the environmental levels of desflurane waste anesthetic gas and the desflurane occupational exposure of operating room staff during the anesthesia of large animal veterinary patients.

METHODS

Active environmental sampling was performed using single-beam infrared spectrophotometry. Passive sampling with dosimeter badges was used to measure the occupational exposure of anesthesia and operating room staff.

RESULTS

Higher concentrations of desflurane (n = 16) were measured at all recovery timepoints relative to the concentrations measured at all locations and timepoints at the start of anesthesia and surgery ( P < 0.05). Time-weighted average desflurane concentrations from dosimeter badges (n = 310) were higher for anesthesia staff than for other operating room personnel ( P < 0.0001).

CONCLUSIONS

The anesthetic recovery of large animal patients is a period of increased exposure to desflurane waste anesthetic gas for veterinary staff.

Volatile capture technology in sustainable anaesthetic practice: a narrative review

Anaesthetic practice contributes to climate change. Volatile capture technology, typically based on adsorption to a carbon- or silica-based substrate, has the potential to mitigate some of the harmful effects of using halogenated hydrocarbons. Anaesthetists have a professional responsibility to use anaesthetic agents which offer the greatest safety and clinical benefit with the lowest financial cost and environmental impacts. Inhalational anaesthetics should be used at an appropriate concentration with a minimal fresh gas flow via a circle system to minimise unnecessary waste. Once practice efficiencies have been maximised, only then should technical solutions such as volatile capture be employed. In this narrative review, we focus on the available literature relating to volatile capture technology, obtained via a targeted literature search and through contacting manufacturers and researchers. We found six studies focusing on the Blue-Zone Technologies Deltasorb®, SageTech Medical SID and Baxter/ZeoSys CONTRAfluran™ volatile capture systems. Though laboratory analyses of available systems suggest that > 95% in vitro mass transfer is possible for all three systems, the in vivo results for capture efficiency vary from 25% to 73%. Currently, there is no financial incentive for healthcare organisations to capture waste anaesthetic gases, and so the value of volatile capture technology requires quantification. System-level organisations, such as Greener NHS, are best positioned to commission such evaluations and make policy decisions to guide investment. Further research using volatile capture technology in real-world settings is necessary and we highlight some priority research questions to improve our understanding of the utility of this group of technologies.

Associations Between Fresh Gas Flow and Duration of Anesthetic on the Maximum Potential Benefit of Anesthetic Gas Capture in Operating Rooms and in Postanesthesia Care Units to Capture Waste Anesthetic Gas

BACKGROUND

Sevoflurane and desflurane are halogenated hydrocarbons with global warming potential. We examined the maximum potential benefit assuming 100% efficiency of waste gas capture technology used in operating rooms and recovery locations.

METHODS

We performed computer simulations of adult patients using the default settings of the Gas Man software program, including the desflurane vaporizer setting of 9% and the sevoflurane vaporizer setting of 3.7%. We performed 21 simulations with desflurane and 21 simulations with sevoflurane, the count of 21 = 1 simulation with 0-hour maintenance + (1, 2, 3, 4, or 5 hours of maintenance) × (0.5, 1, 2, or 4 L per minute fresh gas flow during maintenance).

RESULTS

(1) A completely efficient gas capture system could recover a substantive amount of agent even when the case is managed with low flows. All simulations had at least 22 mL agent recovered per case, considerably greater than the 12 mL that we considered the minimum volume of economic and environmental importance. (2) All 42 simulations had at least 73% recovery of the total agent administered, considerably greater than the median 52% recovery measured during an experimental study with one gas capture technology and desflurane. (3) The maximum percentage desflurane (or sevoflurane) that could be captured decreased substantively with progressively longer duration anesthetics for low-flow anesthetics but not for higher-flow anesthetics. However, for all 8 combinations of drug and liters per minute simulated, there was a substantively greater recovery in milliliters of agent for longer duration anesthetics. In other words, if gas capture could be near perfectly efficient, it would have greater utility per case for longer duration anesthetics. (4) Even using a 100% efficient gas capture process, at most 6 mL liquid desflurane or 3 mL sevoflurane per case would be exhaled during the patient's stay in the postanesthesia care unit. Therefore, the volume of agent exhaled during the first 1 hour postoperatively is not a substantial amount from an environmental and economic perspective to warrant consideration of agent capture by having all these patients in the postanesthesia care unit, or equivalent locations, using the specialized anesthetic gas scavenging masks with access to the hospital scavenging system at each bed.

CONCLUSIONS

Simulations with Gas Man show a strong rationale based on agent uptake and distribution for using volatile anesthetic agent capture in operating rooms if the technology can be highly efficient at volatile agent recovery.

Environmental and Occupational Considerations of Anesthesia: A Narrative Review and Update

With an estimated worldwide volume of 266 million surgeries in 2015, the call for general inhalation anesthesia is considerable. However, widely used volatile anesthetics such as N2O and the highly fluorinated gases sevoflurane, desflurane, and isoflurane are greenhouse gases, ozone-depleting agents, or both. Because these agents undergo minimal metabolism in the body during clinical use and are primarily (≥95%) eliminated unchanged via exhalation, waste anesthetic gases (WAGs) in operating rooms and postanesthesia care units can pose a challenge for overall elimination and occupational exposure. The chemical properties and global warming impacts of these gases vary, with atmospheric lifetimes of 1-5 years for sevoflurane, 3-6 years for isoflurane, 9-21 years for desflurane, and 114 years for N2O. Additionally, the use of N2O as a carrier gas for the inhalation anesthetics and as a supplement to intravenous (IV) anesthetics further contributes to these impacts. At the same time, unscavenged WAGs can result in chronic occupational exposure of health care workers to potential associated adverse health effects. Few adverse effects associated with WAGs have been documented, however, when workplace exposure limits are implemented. Specific measures that can help reduce occupational exposure and the environmental impact of inhaled anesthetics include efficient ventilation and scavenging systems, regular monitoring of airborne concentrations of waste gases to remain below recommended limits, ensuring that anesthesia equipment is well maintained, avoiding desflurane and N2O if possible, and minimizing fresh gas flow rates (eg, use of low-flow anesthesia). One alternative to volatile anesthetics may be total intravenous anesthesia (TIVA). While TIVA is not associated with the risks of occupational exposure or atmospheric pollution that are inherent to volatile anesthetic gases, clinical considerations should be weighed in the choice of agent. Appropriate procedures for the disposal of IV anesthetics must be followed to minimize any potential for negative environmental effects. Overall, although their contributions are relatively low compared with those of other human-produced substances, inhaled anesthetics are intrinsically potent greenhouse gases and pose a risk to operating-room personnel if not properly managed and scavenged. Factors to reduce waste and minimize the future impact of these substances should be considered.

Inhaled Anesthetics: Environmental Role, Occupational Risk, and Clinical Use

Inhaled anesthetics have been in clinical use for over 150 years and are still commonly used in daily practice. The initial view of inhaled anesthetics as indispensable for general anesthesia has evolved during the years and, currently, its general use has even been questioned. Beyond the traditional risks inherent to any drug in use, inhaled anesthetics are exceptionally strong greenhouse gases (GHG) and may pose considerable occupational risks. This emphasizes the importance of evaluating and considering its use in clinical practices. Despite the overwhelming scientific evidence of worsening climate changes, control measures are very slowly implemented. Therefore, it is the responsibility of all society sectors, including the health sector to maximally decrease GHG emissions where possible. Within the field of anesthesia, the potential to reduce GHG emissions can be briefly summarized as follows: Stop or avoid the use of nitrous oxide (N2O) and desflurane, consider the use of total intravenous or local-regional anesthesia, invest in the development of new technologies to minimize volatile anesthetics consumption, scavenging systems, and destruction of waste gas. The improved and sustained awareness of the medical community regarding the climate impact of inhaled anesthetics is mandatory to bring change in the current practice.

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.