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The environmental impact of commonly used inhalation anaesthetic agents is significant, and it is up to anaesthetists to lead the way in implementing sustainable solutions, writes Yannick De Silva …
MUCH of the media report carbon dioxide (CO2) emissions but fail to address the impact that volatile inhaled anaesthetic gases have on the environment. Desflurane, in particular, is thousands of times more potent than CO2 and is a significant contributor to greenhouse gas emissions. Despite contributing to only 0.01–0.10% of total global CO2 emissions, the impact of inhaled anaesthetics on the environment is partially preventable, especially for more potent gases such as desflurane and nitrous oxide (N2O). In light of this, systemic behaviour change among anaesthetists can prompt environmentally sustainable practices across the entire perioperative period. The effects of these emissions ultimately cause higher temperatures for current and future generations. N2O, a gas that may be combined with volatile gases due to the second-gas uptake effect, contributes to the destruction of the ozone layer. This permits more ultraviolet radiation to the earth, making us more susceptible to skin damage and melanoma. As N2O is less potent than other inhaled anaesthetics, it must be used in high concentrations to achieve a clinically effective dose. More than 95% of the anaesthetic gases used during surgery are exhaled and indirectly vented into the atmosphere. This may be following release from a hospital’s anaesthetic gas scavenging system, via leaks in anaesthetic machine valves and manifolds, or through the venting of part-full N2O gas cylinders once returned to the supplier. When used as a combination, desflurane and N2O have significantly higher global warming potential compared with other flurane-N2O combinations. We can liken the CO2 emissions of these volatile gases to the equivalent emissions from driving with one minimal alveolar concentration (MAC)-hour. One MAC-hour represents the amount of anaesthesia required to achieve a specific gas’s MAC for a one hour operation, with N2O and desflurane producing CO2 emissions equating to 95 km and 320 km of driving respectively. Furthermore, although desflurane exerts most of its environmental effect over the initial 20 years after use, N2O has longer-lasting impacts that can span over 100 years following its use. This poses obvious threats to our current and future generations.
What are the solutions?
When considering pragmatic solutions, it is important for anaesthetists to make shared decisions with the patient in the preoperative period, without compromising the quality of care of the patient. Anaesthetists should involve the patient in the discussion and consider their ideas, concerns and expectations. A suggested, clinical practice response is to recycle unmetabolised exhaled gas using a closed circle system — a closed-loop concept that allows anaesthetic gas to be re-breathed after passing through a CO2 absorber. Even though a minimal amount of fresh volatile and N2O gas is added to the mix, the system allows the fresh gas flow to be minimised during an operation. This ultimately reduces the environmental impacts of these gases. However, a circle system requires more complex monitoring and CO2 absorption practices compared with a semi-closed system. This is based on the premise that the inspired gas composition of recycled anaesthetic gases is not known. A cost analysis by Humphrey found that the benefits of a circle system only become significant with operations longer than one hour in duration, where the cost savings from reduced fresh gas flow over a longer period outweigh the capital costs to establish a complex system.
Another clinical response for anaesthetic providers is to avoid the routine use of desflurane and N2O in practice. This can involve physically moving the desflurane vapouriser cartridges away from the anaesthetic machine in place of other volatile gases such as sevoflurane. As a result, an active and conscious decision must be made to use desflurane during the surgery. Alternatively, anaesthetists can opt for regional blocks or total intravenous anaesthesia instead. While some providers may see this as more challenging, it can be an environmentally conscious solution for certain surgeries such as gastroscopic and colonoscopic procedures. Finally, if gases must be used, such as if a patient has difficult intravenous access, then a response can be to reduce fresh gas flow, especially during the maintenance phase while the patient is anaesthetised.
Anaesthesia providers have a duty and responsibility to advocate for systems changes in their workplace and the broader medical community. Through a collaborative approach with colleagues, gas suppliers, hospital quality improvement teams, and sustainability officers, anaesthetists can promote environmentally sustainable behaviour. This behaviour can be fostered through formal continuing medical education in stewardship principles and planetary health, which may incentivise stakeholders to actively participate in the culture change. To have lasting systems changes, anaesthetists should begin by fostering a perioperative culture that values sustainability and resource stewardship. They can contribute to life cycle assessments for the gases in their formulary, following a “cradle-to-grave” approach in the process. Anaesthetists with an interest in research can lead sustainability audits within their hospitals and health networks, eventually publishing their results as open-source data. They can also advocate for infrastructure development in their hospitals, particularly by voicing the needs of resource-limited settings. For their own hospitals, anaesthetists can recommend sustainable redesign for proposed renovations of their operating theatres, and work in conjunction with building and engineering teams. They can design and follow a “5R” approach to minimising aneasthetic waste, incorporating the principles of reducing, reusing, recycling, rethinking and researching. Finally, it would be beneficial to incorporate and strengthen environmental sustainability principles in anaesthetic training programs and continuous professional development courses. This approach has proven successful in medical schools around Australia, such as with the Joint Medical Program at the University of Newcastle and the University of New England. As part of the Joint Medical Program, third-year medical students are required to produce a video discussing sustainable health care in any clinical area of interest. Engaging with students at a grassroots level has the potential to foster environmental sustainability changes well into the future. Sustainable anaesthetic practices have also received attention from collaborative groups in Australia, such as TRA2SH (Trainee-led Research and Audit in Anaesthesia for Sustainability in Healthcare). This anaesthetic trainee-led group aims for various quality improvements, including the complete removal of desflurane from hospital formularies.
Where to from here?
The environmental impacts of desflurane and N2O, commonly used inhalation anaesthetic agents used during surgery, cannot be underestimated. Specifically, desflurane contributes to greenhouse gas emissions and increases surface temperatures on our planet. N2O, on the other hand, causes destruction of the ozone layer destruction of the ozone layer and makes us susceptible to ultraviolet radiation. Anaesthetists can undertake pragmatic clinical practice solutions to make meaningful systems changes. Ultimately, it is the responsibility of our health care providers to seed environmentally conscious behaviour amongst their colleagues, communities and networks. It would be interesting to survey whether the environmental impact of anaesthetic gases feature in the preoperative discussion between anaesthetist and patient. It would also be worthwhile to explore whether other causes of perioperative environmental waste, such as single-use syringes and laryngoscopes, form part of this conversation.
Yannick De Silva is a 4th-year medical student at the University of Newcastle. In his spare time, he volunteers with St John Ambulance as a Clinical Educator and Advanced First Aid Responder. He is also the current Chair of Hunter Spartans (Student, Prevocational and Registrar Trials and Audit Network), a collaborative research group in the Hunter. He is passionate about anaesthesia, medical education and collaborative health care.
The statements or opinions expressed in this article reflect the views of the authors and do not necessarily represent the official policy of the AMA, the MJA or InSight+ unless so stated.
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Recycling, switching to a plant-based diet, walking or riding a bicycle to work are all great activities most of us can do to reduce our carbon footprint. All of these are completely wiped out by using desflurane, the impact of which is remarkably higher. Our hospital system still allows desflurane usage without a capture system, and no amount of evidence can get at least some members to switch to TIVA, let alone sevoflurane. Surprisingly, N2O is rarely used (due to it’s contribution in causing PONV) by these same members.
As the author volunteers with St John’s Ambulance, it is salutary to compare his figures “N2O and desflurane producing CO2 emissions equating to 95 km and 320 km of driving respectively” with the retrieval Ambulance/helicopter’s emissions. Including the embedded carbon costs of the custom fitout of road and air ambulances, and accounting for their return trip. The recent deaths of a pilot and trainee at Hobart airport during training of an emergency helicopter pilot, remind us that many ‘non-clinical’ hours of carbon emissions are necessary to maximise aviation safety.
Rather than focus on outmoded drugs, the low-hanging fruit is in the storage systems. Multidose ampoules were commonly used last century for an operative list. These were withdrawn because of theoretical AIDS contamination risk, yet have seen a resurgence as all Covid vaccines come in multidose ampoules. No cases of cross-contamination with blood-borne viruses have been reported in tens of millions of doses. Allowing anaesthetists to carefully use multidose ampoules would minimise waste packaging, and discarding of perfectly good drugs (with their embedded carbon cost of production) at the end of each procedure. It would also have the advantage of applying to any drug, ie would not become irrelevant as desflurane etc go out of fashion on clinical grounds.
Current anaesthesia practice already incorporates most of this. Modern anaesthesia machines have the agent monitoring required for minimal flow or closed circle anaesthesia. Desflurane has already been removed from routine use in many hospitals. Nitrous oxide has largely disappeared from adult inhalational anaesthesia over the last two decades and the use of TIVA has increased rapidly. Most anaesthetists are acutely conscious of the potential environmental impact of their work.
This company has identified a solution to anaesthetic capture and recycling, just needing partnerships to further the development. https://www.sagetechmedical.com/
Yannick, has someone done the numbers on desflurane vs a plant-based diet and their respective effect on global heating? I would think if an anaesthetist were so passionate about reducing their desflurane related greenhouse effect , then they should be equally as passionate about how the very food they eat every day also contributes to climate change. The most effective way of reducing one’s everyday global warming impact is to eat plant based.
Valuable as much for its clarity (plain language) as for the outline of the issues, practical explanation and advocacy. Perhaps a follow up could include alternatives, and in-depth consideration of the balance between sustainability and best quality care and how that is managed.
Desflurane and Nitrous oxide are no longer used routinely in anaesthesia practice. Many hospitals have eliminated desflurane altogether. The environmental impact of anaesthesia practices has been a topic under discussion and has resulted in action for many years. Closed circuit systems are used in almost all cases.