INTRODUCTION Climate change has been identified as the single greatest public health threat of the 21st century.[1] The healthcare sector is a major contributor to global warming, accounting for 4.4% of total greenhouse gas emissions.[2] While healthcare contributes 3.4% of Singapore's emissions, Singapore is placed second globally in healthcare per capita emissions.[3,4] National University Hospital (NUH) is a 1200-bedded tertiary care hospital in Singapore and a member of the National University Health System (NUHS) healthcare cluster. In 2021, NUHS set a goal to reduce its total carbon emissions by 25% by 2030, across all scopes of emissions. The NUH Department of Anaesthesia is working towards this goal. The aim of this study was to provide a pragmatic guide for anaesthesia departments to decarbonise anaesthesia practices and enable environmentally sustainable care. We described the assessment of carbon footprint and identification of high-emission areas in our anaesthesia department, as well as the constraints faced — what can and cannot be controlled — in our decarbonisation efforts. METHODS The NUH anaesthesia department's carbon footprint, including emissions from anaesthetic gases, electricity consumption in the operating room (OR), waste, consumables, pharmaceuticals and conference travel, was assessed. These were quantified in carbon dioxide equivalents (CO2e) as a uniform currency for all scopes and types of emissions, and are detailed in the Supplemental Digital Appendix at https://links.lww.com/SGMJ/A105. We used a combined approach of bottom-up activity-based carbon footprint analysis and top-down calculations using emission factors from environmentally extended input–output (EEIO) economic databases. Following a data hierarchy, activity-based emissions factors were used first where available, followed by those from EEIO databases for goods and services. For inhalational anaesthesia drugs, annual volumes of the drugs purchased were obtained from pharmacy, and carbon emissions were calculated based on the latest global warming potential (GWP100) data.[5,6] In our department, desflurane was commonly used before 2021. Sustained educational efforts had been taken and environmental campaigning carried out on the environmental impact of desflurane and nitrous oxide (N2O).[7] For other anaesthesia drugs, the carbon footprint was calculated using aggregate expenditure and a Singapore-specific spend-based emission factor referenced from the environmentally extended Eora multiregional EEIO database.[8] For equipment, the carbon footprint was also calculated using annual expenditure and spend-based emission factors.[8] Hospital waste data were obtained from the environmental services department. An audit of OR waste was conducted to determine the proportions of different waste types. The proportion of OR waste from anaesthesia was estimated. The carbon footprint of recycled waste was assumed to be negligible.[9] The carbon footprint of chemical waste was based on the weight of soda lime used. Polyvinyl chloride (PVC) is used for medical equipment such as intravenous fluid bags, oxygen masks and nasal prongs. We calculated the reduction in CO2e from recycling PVC instead of incineration. Electricity usage was estimated based on the floor space area. Post-anaesthesia care units, offices and changing rooms were assumed to have similar energy use intensity (EUI) as the rest of the hospital, while ORs were assumed to have higher EUI.[10] Our department turns off anaesthesia gas scavenging systems (AGSS) during out-of-office hours as these account for substantial energy usage.[11] Departmental overseas conference travel records and emission factors from the Department for Energy Security and Net Zero and the Department for Business, Energy and Industrial Strategy greenhouse gas reporting, and the Oversea-Chinese Banking Corporation Limited Climate Index were used to calculate the CO2e of air and car travel, respectively.[12,13] This included well-to-tank emissions. RESULTS Anaesthesia inhalational drugs and electricity consumption contributed the most to our carbon footprint in 2022 [Figure 1]. Inhalational anaesthetic drugs and medical gases accounted for 2006.79 tCO2e in 2022. This was 1.68% of the hospital's total carbon footprint or 32% of the department's carbon footprint.[7,14] Desflurane usage has reduced by over 80% in the last 2 years. The department's total carbon footprint from anaesthesia drugs, including that of propofol and its associated consumables, decreased accordingly [Figure 2]. This reduction was achieved while the general anaesthesia workload increased by 23%.Figure 1: Chart shows the summary of the department's carbon footprint in 2022. OR: operating roomFigure 2: Chart shows the department's anaesthetic agent use and the associated carbon footprint for all general anaesthesia (GA) drugs over the last few years. tCO2e: tonnes of CO2 equivalentIn 2019, N2O accounted for 65% of the emissions from inhalational anaesthesia drugs in our hospital.[14] This proportion increased to 84% due to reduced desflurane usage. Much of N2O usage was for labour analgesia in the delivery suite. We are in the process of switching to cylinders mounted on anaesthesia machines and turning off N2O pipelines to certain OR complexes. The carbon footprint from equipment and consumables was estimated at 563.28 tCO2e. For other anaesthesia drugs, the spend-based carbon footprint was 771.06 tCO2e. Calculations based on the footprint of active pharmaceutical ingredient (API) was much lower at 6.04 tCO2e, as it included only the carbon footprint of API and not of packaging, freight and distribution. With regards to waste management, the carbon footprint was based on our hospital's waste audit.[14] The ORs generated 30%–40% of the hospital's total waste, and anaesthesia contributed to 25% of the OR waste, like in other hospitals.[15,16,17] Anaesthesia waste in our hospital accounted for 382.84 tCO2e. The packaging for sterile items and drugs contributed the most to this waste. The total weight of our PVC waste in 2022 was approximately 27,000 kg. All of this was incinerated. We partnered with a local PVC recycling company to collect and reprocess our PVC waste into new products.[18] By recycling our PVC waste, we would save approximately 7.5 tCO2e per year from clinical waste incineration. The department is also piloting the reprocessing of uncontaminated syringes into bitumen for road resurfacing.[19] Electricity usage from ORs was estimated to contribute 2474.67 tCO2e. As there were no submeters for individual ORs, the reduction in electricity from turning off AGSS could not be measured directly. Business travel was estimated to contribute 54.74 tCO2e. DISCUSSION Data and carbon footprint assessments can help a department to focus on and monitor its environmental sustainability efforts. For some product categories, carbon footprints have to be calculated using spend-based emission factors, which are industry and country averages and not manufacturer or product specific. These provide visibility on the important contributors, and enable target setting and tracking of decarbonisation. Our sustainability efforts followed our department's principle to 'reduce first', targeting the reduction of high-impact and controllable items such as solid waste recycling and desflurane use. Changing staff understanding and behaviour takes time, particularly in resource-rich environments. Despite continuous education on GWP100 of anaesthetic gases, some anaesthetists still choose to use desflurane and N2O. Anaesthetists may not want to change their practice due to concerns about affecting their patients' outcomes or efficiency of case turnover.[20] While there is a possibility of vapour capture for desflurane and cracking devices for N2O in the near future, the focus should be to reduce their usage. More work is required to encourage intergenerational thinking to change mindsets, balancing sustainability with physician's complete autonomy for clinical decisions. After reducing the usage of equipment, reusing is the next best option. The net environmental effect of reusable versus single-use equipment is a complex calculation that depends on the local energy source used in processing equipment.[21] Natural gas is used for 95% of Singapore's energy needs, and the grid emissions factor is favourable for switching to reusable equipment.[22,23] There are hidden costs of disposal, especially in a land-scarce country, and there is a need to change our understanding from a cradle-to-gate to a cradle-to-grave approach.[24] There is a lack of circularity with our medical equipment, with limited remanufacturing and recycling processes by our suppliers. We are also limited in on-site resterilisation capacity due to staffing and space constraints. While reducing energy use, water use and waste generation is a good starting point for organisations, our department considered its scope of responsibility to extend beyond these. We first ascertained easily controllable changes that did not require staff consensus, such as turning off AGSS and reducing air changes per hour (ACH) in ORs after office hours, and changing to light-emitting diode light bulbs. In terms of per floor area square metre, ORs consume a lot of energy, ranging from three to six times that of other facilities in the hospital.[11] Air conditioning and mechanical ventilation systems account for 50%–60% of hospital energy usage. This is more pronounced in ORs due to the single-pass high ACH required to maintain air quality and prevent particle accumulation and infection during surgery.[25] The ACH may be reduced during nonoperating hours, with guidelines recommending a minimum of six ACH to maintain positive pressure and indoor air quality.[26,27] An infection control study showed that turning off OR ventilation at night and restarting it 30 min before surgical activity did not affect the particle or microbial count.[28] Changing 100% single pass to some recirculation of air after high-efficiency particulate air filtering can also help reduce energy use.[26] While not all of ORs' energy usage is attributable to anaesthesia, we have included it, as anaesthetists can influence the saving of electricity. Drug choices, daily commutes and travel for overseas conferences involve staff choices and have to be addressed through education. Even with engagement and provision of alternatives, there may be limited change, as personal choice, convenience and preference may prevail. As the cost of externalities of the department's carbon footprint is borne by others and future generations, this may not incentivise change. As most of the overseas conference travel is by air, we have suggested to our department to consider virtual meetings and teleconferencing whenever possible. Implementing carbon pricing into future travel budgets can be considered. Recycling is enabled by segregation at source, requiring more receptacles and storage space. Due to space constraints, hospitals have to prioritise recycling streams that have the most environmental benefit. Future planning of hospitals should provide adequate operating and storage space for reprocessing and resterilisation of equipment and waste segregation for recycling. As Singapore's energy supply decarbonises, resterilisation's carbon footprint will reduce, supporting its application. There were several limitations associated with carbon footprinting. There were no electrical submeters in our ORs, and OR electricity consumption was estimated. There was also a lack of anaesthesia and OR-specific EUI benchmarks. The waste streams had very high tonnage and volume, and hence sampling was used to quantify OR and anaesthesia waste. The list of equipment included in carbon footprinting is not exhaustive due to the practicalities involved. This study focused on the departments' operational carbon footprint, and not the embodied carbon in major capital purchases or building of new facilities. These capital items are not regular purchases; they are used for several years and their embodied carbon will be addressed separately. Carbon emissions from staff travel to and from the hospital were not included in the scope of this paper. Overseas conference travel was below average during the immediate post-coronavirus disease 2019 pandemic era. In conclusion, anaesthetists can make decisions to reduce greenhouse gas emissions and build a sustainable healthcare system for future generations. Measuring a department's carbon emissions can help to determine hotspots and guide interventions. Decarbonisation can be achieved without impacting quality of care and patient safety. Education and awareness can help influence changes. Acknowledgements We would like to thank Dr Bryan Tan, Head of Department, Department of Anaesthesia, National University Hospital, Singapore, for reviewing our paper and all staff who helped with data extraction. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
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