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Environmental sustainability in veterinary anaesthesia

Published:February 08, 2019DOI:https://doi.org/10.1016/j.vaa.2018.12.008

      Abstract

      Objective

      Attention is drawn to the potential of global warming to influence the health and wellbeing of the human race. There is increasing public and governmental pressure on healthcare organisations to mitigate and adapt to the climate changes that are occurring. The science of anaesthetic agents such as nitrous oxide and the halogenated anaesthetic agents such as greenhouse gases and ozone-depleting agents is discussed and quantified. Additional environmental impacts of healthcare systems are explored. The role of noninhalational anaesthetic pharmaceuticals is discussed, including the environmental life-cycle analyses of their manufacture, transport, disposal and use. The significant role of anaesthetists in recycling and waste management, resource use (particularly plastics, water and energy) and engagement in sustainability are discussed. Finally, future directions for sustainability in veterinary anaesthesia are proposed.

      Conclusions

      Veterinary anaesthetists have a considerable opportunity to drive sustainability within their organisations through modification of their practice, research and education. The principles of sustainability may help veterinary anaesthetists to mitigate and adapt to our environmental crisis. Due to their particular impact as greenhouse gases, anaesthetic agents should be used conservatively with the lowest safe fresh gas flow possible. Technologies for reprocessing anaesthetic agents are described.

      Keywords

      Introduction

      In 2010, climate change was called ‘potentially the biggest global health threat of the 21st century’ by The Lancet (
      • Costello A.
      • Abbas M.
      • Allen A.
      • et al.
      Managing the health effects of climate change. Lancet and University College London Institute for Global Health Commission.
      ). Awareness of the impacts of human activity on the planet is gathering momentum, particularly given the increase in average temperatures since the 1960s (
      Intergovernmental Panel on Climate Change
      Summary for Policymakers.
      ). In the year 2000 alone, climate change was estimated to be responsible for the loss of 5.5 million disability-adjusted life years (
      • Campbell-Lendrum D.H.
      • Corvalán C.F.
      • Prüss–Ustün A.
      How much disease could climate change cause?.
      ). The healthcare effects of climate change are likely to disproportionately affect those who have least access to the world’s resources and those who have contributed least to its cause (
      • Costello A.
      • Abbas M.
      • Allen A.
      • et al.
      Managing the health effects of climate change. Lancet and University College London Institute for Global Health Commission.
      ). In 2015, at the Paris International Climate Conference, 195 countries made legal commitments to take action in limiting global warming to less than 2°C above preindustrial average temperatures, to which end the European Union has stated targets of 40% reduction (from 1990 levels) in carbon emissions by 2030 (). Even these targets may prove insufficient to prevent significant climate change (
      • Steffen W.
      • Röckstrom J.
      • Richardson K.
      • et al.
      Trajectories of the Earth System in the Anthropocene.
      ), and the Intergovernmental Panel on Climate Change has subsequently recommended limiting global warming to 1.5°C to reduce challenging impacts on ecosystems, human health and wellbeing (
      Intergovernmental Panel on Climate Change
      Summary for Policymakers: Global Warming of 1.5 °C. IPCC, Republic of Korea.
      ). The medical profession is facing policy and healthcare pressures which have forced engagement with environmental issues (
      • McCoy D.
      • Hoskins B.
      The science of anthropogenic climate change: what every doctor should know.
      ,
      • Weiss A.
      • Hollandsworth H.M.
      • Alseidi A.
      • et al.
      Environmentalism in surgical practice.
      ). Healthcare systems must develop strategies to mitigate (avoid the unmanageable) and adapt (manage the unavoidable) to environmental pressures. In this article, we discuss the environmental issues which affect veterinary anaesthetists and suggest how we can promote resilience within the industry in the face of ecological changes.
      For this article, the relevant literature was identified using the terms ‘sustainability’, ‘climate change’ and ‘anaesthesia’ entered into the databases Scopus and Google in July 2018. The reference lists of retrieved papers were examined to identify further studies and sources for inclusion. There were no exclusion criteria.

      Why sustainability?

      As early as 1975, it was suggested that halogenated anaesthetic agents had the potential to harm the global environment (
      • Fox J.W.C.
      • Fox E.
      • Villanueva R.
      Stratospheric ozone destruction and halogenated anaesthetics.
      ) and whilst this particular impact remains a concern, our interest must extend beyond the discussion surrounding anaesthetic agents. Broader assessments of the impacts of healthcare systems make for startling reading; in 2013, the United States of America (USA) healthcare sector was estimated to be responsible for 12% of acid rain, 10% of smog formation, 9% of air pollutants and 1–2% of air toxins nationally (
      • Eckelman M.J.
      • Sherman J.
      Environmental impacts of the U.S. health care system and effects on public health.
      ). Ecological concerns include carbon emissions, ozone depletion, biopersistence, respiratory toxicosis, carcinogens, water acidification, eutrophication (excess nutrients leading to algae blooms) and aquatic ecotoxicity.
      Sustainable development has been defined by the Brundtland Commission as ‘development that meets the needs of the present without compromising the ability of future generations to meet their own needs’ (
      • United Nations
      Our common future – Brundtland Report: Report of the World Commission on Environment and Development.
      ). Furthermore, three pillars of sustainability were stated by the United Nations (UN): 1) environmental protection; 2) economic growth; and 3) social progress (
      • United Nations
      Johannesburg Declaration on Sustainable Development - Report of the World Summit on Sustainable Development.
      ), also known as the triple bottom line of ‘planet, profit and people’. Introducing sustainability into veterinary anaesthesia will require a paradigm shift in approach; sustainability implies a lean and resilient working ethos which prioritizes preventative and holistic solutions and is likely to produce environmental, financial and health cobenefits. It will require action in multiple areas, including pharmaceuticals, waste and resource management, procurement, travel and leadership. As an interface between multiple clinical areas, veterinary anaesthetists are ideally placed to have an impact on institutional sustainability. In this article, we suggest opportunities to champion sustainable practices within veterinary organizations.

      Anaesthetic agents as greenhouse gases

      Whilst the effects of anaesthetic gases on atmosphere have been comprehensively reviewed in detail (
      • Campbell M.
      • Pierce J.M.T.
      Atmospheric science, anaesthesia, and the environment.
      ), they are summarized here to highlight the areas of concern. Solar energy is essential for life on Earth. After being absorbed by the Earth’s surface, solar energy is reemitted as infrared thermal radiation. Greenhouse gases and vapours (GHGs) are compounds that have a significant atmospheric lifetime and possess infrared absorption bands that overlap with the outgoing radiation from the Earth’s lower atmosphere (
      • Andersen M.P.S.
      • Nielsen O.J.
      • Wallington T.J.
      • et al.
      Assessing the impact on global climate from general anesthetic gases.
      ). GHGs have the capacity to absorb and reflect solar radiation back to the Earth’s surface. Whilst GHGs serve to maintain a more stable surface temperature through night and day, higher concentrations will correspondingly maintain a higher surface temperature.
      A marked and rapid increase in the atmospheric carbon dioxide concentrations has occurred since around the industrial era in the 1800s (
      • Brook E.J.
      • Buizert C.
      Antarctic and global climate history viewed from ice cores.
      ). The Intergovernmental Panel on Climate Change (IPCC) concluded that ‘most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations’ (
      Intergovernmental Panel on Climate Change
      Summary for Policymakers.
      ). The problems associated with temperature rises include increasing disease burden from heat waves, droughts, malnutrition, diarrhoea, cardiorespiratory and infectious diseases, flooding of coastal areas but decreased water availability elsewhere, and loss of ecosystems including habitats and species (
      • Costello A.
      • Abbas M.
      • Allen A.
      • et al.
      Managing the health effects of climate change. Lancet and University College London Institute for Global Health Commission.
      ).
      The GHGs include carbon dioxide, methane, nitrous oxide, water and all of the halogenated anaesthetic agents in common use (
      • Campbell M.
      • Pierce J.M.T.
      Atmospheric science, anaesthesia, and the environment.
      ). Since multiple GHGs exist, it is their combined effect that matters; this is evaluated using carbon dioxide equivalents (CO2e, kg). It has been estimated that the annual global climatic impact of anaesthetic agents released into the atmosphere is 4.4 million tonnes of CO2e, which is roughly equivalent to one coal-powered station or 1 million passenger cars (
      • Andersen M.P.S.
      • Sander S.P.
      • Nielsen O.J.
      • et al.
      Inhalation anaesthetics and climate change.
      ). By comparison, the global emissions of GHGs are estimated as 49 gigatonnes CO2e per year, of which 24% originate from agriculture and other land use and 14% from the transport sector (
      Intergovernmental Panel on Climate Change
      Summary for Policymakers.
      ), whilst only around 2.1% originate from healthcare in developed countries (
      • Wyssusek K.H.
      • Keys M.T.
      • van Zundert A.A.J.
      Operating room greening initiatives – the old, the new, and the way forward: A narrative review.
      ). Anaesthetic gases contribute around 5% of the total carbon emissions of the acute healthcare facilities within the National Health Service (NHS) for England; to compare, the gas used to heat NHS England’s buildings and water produces 11% of the total carbon emissions (). Although anaesthetic gases contribute a relatively low amount to global carbon emissions, and are present at vastly lower concentrations than carbon dioxide, they are disproportionately effective as GHGs since they absorb infrared radiation at around 10 μm. This overlaps with an infrared spectral range or atmospheric window of approximately 8–14 μm where absorption of radiation by any naturally occurring GHG is relatively minor (
      • Andersen M.P.S.
      • Nielsen O.J.
      • Wallington T.J.
      • et al.
      Assessing the impact on global climate from general anesthetic gases.
      ). This atmospheric window is an important mechanism by which the Earth can cool itself. The importance of each GHG in driving climate change can be quantified using radiative forcing (W m–2), which is a measure of the influence that a factor has in altering the balance of incoming and outgoing energy between the Earth and its atmosphere (
      Intergovernmental Panel on Climate Change
      Summary for Policymakers.
      ). Positive radiative forcing tends to increase the Earth’s surface temperature. The anaesthetic agents are thought to be responsible for 10–15% of total anthropogenic radiative forcing of the climate since preindustrial era (
      • Andersen M.P.S.
      • Nielsen O.J.
      • Wallington T.J.
      • et al.
      Assessing the impact on global climate from general anesthetic gases.
      ).
      Various metrics are used to measure the atmospheric impact of various agents (Table 1). To allow real-time calculation of CO2e during anaesthesia, online spreadsheets or smartphone apps are available (
      • Pierce J.M.T.
      CO2e and cost calculator of inhalational anaesthesia; Anesthetic Impact Calculator (Sleekwater Software).
      ,
      • Yale University
      Yale Gassing Greener 2.0.2 app.
      ) and can be used to highlight the effects of different practices. The total greenhouse emissions (CO2e, kg) caused directly and indirectly by a person, organization, event or product can be referred to as its carbon footprint (
      • Campbell M.
      • Pierce J.M.T.
      Atmospheric science, anaesthesia, and the environment.
      ). The carbon footprint of anaesthetic gases can be calculated by multiplying the total mass released into the atmosphere by the global warming potential over 100 years (GWP100) (
      • Andersen M.P.S.
      • Nielsen O.J.
      • Wallington T.J.
      • et al.
      Assessing the impact on global climate from general anesthetic gases.
      ). The GWP100 is a measure of a GHG’s ability to trap heat and can be compared with the GWP100 of carbon dioxide, which is one. GWP100 is calculated based on a compound’s persistence in the atmosphere (or atmospheric lifetime) and how efficiently it reflects solar radiation back to the Earth. Table 1 highlights the particularly high carbon footprints that result from using nitrous oxide and desflurane due to the relatively low potencies of these agents and therefore larger quantities released, longer atmospheric persistence, and in the case of desflurane, a higher radiative forcing effect (
      • Sherman J.
      • Le C.
      • Lamers V.
      • Eckelman M.
      Life cycle greenhouse gas emissions of anesthetic drugs.
      ).
      Table 1The atmospheric characteristics of anaesthetic gases and vapours
      Atmospheric characteristicsNitrous oxideDesfluraneIsofluraneSevofluraneCarbon dioxide
      Atmospheric lifetime (years)
      Campbell & Pierce 2015.
      110143.21.174
      Radiative efficiency (W m–2 ppb–1)
      Andersen et al. 2010.
      0.0030.4690.4530.3510.676
      Global warming potential over 100 years
      Campbell & Pierce 2015.
      31025405101301
      Carbon dioxide equivalent (CO2e, kg) per MAC-hour for canine anaesthesia
      Steffey et al. 2017.
      at 1 L minute–1 oxygen
      Pierce 2015.
      36
      Assuming nitrous oxide and oxygen combined at 1 L minute−1 each to vaporize sevoflurane.
      8931
      Equivalent to car driving (miles) per MAC-hour of canine anaesthesia at 1 L minute–1 oxygen
      Assuming United Kingdom average car emissions of 160 gCO2 km–1 (256 gCO2 mile–1).
      140
      Assuming nitrous oxide and oxygen combined at 1 L minute−1 each to vaporize sevoflurane.
      348124
      MAC, minimum alveolar concentration.
      • Campbell M.
      • Pierce J.M.T.
      Atmospheric science, anaesthesia, and the environment.
      .
      • Andersen M.P.S.
      • Sander S.P.
      • Nielsen O.J.
      • et al.
      Inhalation anaesthetics and climate change.
      .
      • Steffey E.P.
      • Mama K.R.
      • Brosnan R.J.
      Inhalation Anesthetics.
      .
      §
      • Pierce J.M.T.
      CO2e and cost calculator of inhalational anaesthesia; Anesthetic Impact Calculator (Sleekwater Software).
      .
      Assuming nitrous oxide and oxygen combined at 1 L minute−1 each to vaporize sevoflurane.
      ∗∗ Assuming United Kingdom average car emissions of 160 gCO2 km–1 (256 gCO2 mile–1).
      An additional effect of nitrous oxide, and to a far lesser extent halothane and isoflurane, is the destruction of ozone molecules which limit the transmission of harmful ultraviolet light towards the Earth’s surface (
      • Logan M.
      • Farmer J.G.
      Anaesthesia and the ozone layer.
      ). Nitrous oxide has been described as ‘the single most important ozone-depleting emission… throughout the 21st century’ (
      • Ravishankara A.R.
      • Daniel J.S.
      • Portmann R.W.
      Nitrous oxide (N2O): The dominant ozone-depleting substance emitted in the 21st century.
      ). The global Montreal Protocol to protect the ozone layer was amended in 2016 to control hydrofluorocarbons but not anaesthetic agents (
      • United Nations
      Frequently asked questions relating to the Kigali Amendment to the Montreal Protocol.
      ); this situation may change as the climate crisis develops and the effect of anaesthetic agents becomes proportionately more significant. Whilst medical emissions of atmospheric nitrous oxide are by no means the most significant (they account for less than 4% of all nitrous oxide emissions, with the majority of emissions originating from microbial action on nitrogenous fertilizers) (
      • Campbell M.
      • Pierce J.M.T.
      Atmospheric science, anaesthesia, and the environment.
      ), its environmental harm and atmospheric persistence weighs against its therapeutic benefit in veterinary anaesthesia.
      Xenon is a modern anaesthetic agent which is produced by fractional distillation of air as a by-product of oxygen production. As an inert gas, xenon does not contribute to GHG or ozone depletion; however, 220 watt hours of energy is used to produce 1 L of xenon (
      • Gadani H.
      • Vyas A.
      Anesthetic gases and global warming: Potentials, prevention and future of anesthesia.
      ), which is a similar energy demand per litre to using a desktop computer for 1 hour. Its future use as a clinical anaesthetic agent is only viable if stringent recycling technologies are employed.

      Minimizing inhalational anaesthetic use

      It is clear that we should aim to minimize our use of anaesthetic gases and vapours and discuss eliminating the use of nitrous oxide and desflurane in clinical veterinary anaesthesia altogether. Reductions in anaesthetic gases may be achieved by various means. The simplest methods include using, where appropriate, rebreathing systems and the lowest safe fresh gas flow (FGF). Using low flow (0.5–1 L minute–1), minimal flow (0.25–0.5 L minute–1) or closed circuit techniques (<0.25 L minute–1; or flow equal to metabolic oxygen consumption plus system gas leaks) will reduce expense and waste of anaesthetic gases as well as maintain heat and moisture within the breathing system (
      • Brattwall M.
      • Warrén-Stomberg M.
      • Hesselvik F.
      • Jakobsson J.
      Brief review: theory and practice of minimal fresh gas flow anesthesia.
      ). However, these FGF may be impractical in all clinics due to the increased risk of delivery of a hypoxic mixture due to inadequate denitrogenation, or accumulation of other gases including endogenous compounds (such as methane, water vapour and argon) and exogenous toxins (such as carbon monoxide) (
      • Gregorini P.
      Effect of low fresh gas flow rates on inspired gas composition in a circle absorber system.
      ). Monitoring the inspired oxygen concentration is critical to avoiding hypoxic mixtures when using low FGF (
      • Feldman J.M.
      Managing fresh gas flow to reduce environmental contamination.
      ). Strategies to avoid toxic gas accumulations during low FGF anaesthesia include using absorbents without strong alkalis, avoiding dessication of absorbents and flushing intermittently with high FGF every 30 minutes during anaesthesia (
      • Feldman J.M.
      Managing fresh gas flow to reduce environmental contamination.
      ). At lower FGF, there is also a risk of an inadequate anaesthetic gas concentration due to dilution or failure to appreciate the slow rate of change of anaesthetic concentration; monitoring end-tidal anaesthetic concentrations will mitigate this risk (
      • Brattwall M.
      • Warrén-Stomberg M.
      • Hesselvik F.
      • Jakobsson J.
      Brief review: theory and practice of minimal fresh gas flow anesthesia.
      ). These techniques additionally require vaporizers and flowmeters which can perform accurately at lower flows.
      The effect of increased use of CO2 absorbents at low flows on carbon footprint has not been established. Changing to a practice of turning off FGF rather than the vaporizer will limit agent wastage during such procedures as moving or positioning the patient, or endotracheal intubation following induction of anaesthesia using a mask or chamber system to deliver the anaesthetic agent.
      Newer anaesthetic machines incorporate automated electronic closed-loop technologies to accurately control end-tidal agent concentrations; conflicting results suggest 15% increases (
      • Wetz A.J.
      • Mueller M.M.
      • Walliser K.
      • et al.
      End-tidal control vs. manually controlled minimal-flow anesthesia: a prospective comparative trial.
      ) or 32% and 44% reductions in agent consumption (
      • Özelsel T.
      • Kim S.H.
      • Rashiq S.
      • Tsui B.C.
      A closed-circuit anesthesia ventilator facilitates significant reduction in sevoflurane consumption in clinical practice.
      ) and GHG emissions (
      • Tay S.
      • Weinberg L.
      • Peyton P.
      • et al.
      Financial and environmental costs of manual versus automated control of end-tidal gas concentrations.
      ), respectively, the variation being mainly due to the difference in initial FGF over the first 15 minutes of anaesthesia used by the electronic algorithms to achieve desired inspired oxygen concentrations. Of interest,
      • Tay S.
      • Weinberg L.
      • Peyton P.
      • et al.
      Financial and environmental costs of manual versus automated control of end-tidal gas concentrations.
      found no increase in the cost of CO2 absorbents, although larger (and therefore more efficient) canisters were used in the electronic closed-loop group where lower flows were used. Further investigation of the cost of increased CO2 absorbance is required.
      Use of charcoal and zeolite reflection filters can conserve anaesthetic agents (
      • Sturesson L.W.
      • Frennström J.O.
      • Ilardi M.
      • Reinstrup P.
      Comparing charcoal and zeolite reflection filters for volatile anaesthetics.
      ). Using this principle, an anaesthetic conserving device (AnaConDa; Sedana Medical, Sweden) containing a charcoal filter placed between the endotracheal tube and the breathing system adsorbs and then releases anaesthetic agents. Agent consumption was similar to a circle breathing system at <1.5 L minute–1 FGF, but could reduce agent consumption by 40–75% at higher FGF (<6 L minute–1) (
      • Enlund M.
      • Wiklund L.
      • Lambert H.
      A new device to reduce the consumption of a halogenated anaesthetic agent.
      ,
      • Tempia A.
      • Olivei M.C.
      • Cal za E.
      • et al.
      The anesthetic conserving device compared with conventional circle system used under different flow conditions for inhaled anesthesia.
      ). These are currently used for sedation in medical intensive care units (
      • Kim H.Y.
      • Lee J.E.
      • Kim J.
      Volatile sedation in the intensive care unit: A systematic review and meta-analysis.
      ). Digitally controlled in-line reflectors are under investigation, which may improve precision in delivery of anaesthetic agents and reduce agent consumption by 55% at FGF of 1 L minute–1 (
      • Mashari A.
      • Fedorko L.
      • Fisher J.A.
      • et al.
      High volatile anaesthetic conservation with a digital in-line vaporizer and a reflector.
      ). Any such systems have the potential to increase patient dead space and potentially retain other gases such as carbon dioxide (
      • Sturesson L.W.
      • Frennström J.O.
      • Ilardi M.
      • Reinstrup P.
      Comparing charcoal and zeolite reflection filters for volatile anaesthetics.
      ).
      Most countries have stringent controls on occupational exposure to anaesthetic vapours and gases, which will limit waste gases within the anaesthetic rooms. However, the majority of anaesthetic gases are vented into the atmosphere after use via reservoir and scavenging systems. The only real effective means of reducing anaesthetic agents in the atmosphere is to either capture and recycle them or to render them chemically inert.
      In Canada, a commercially available silica zeolite canister (Deltasorb Canister; Blue-Zone Technologies, Canada) can be attached to the scavenging reservoir and has been shown to completely remove isoflurane from exhaled gases (
      • Doyle J.
      • Byrick R.
      • Filipovic D.
      • Cashin F.
      Silica zeolite scavenging of exhaled isoflurane: A preliminary report.
      ) which is then returned to the company for extraction and reprocessing of the anaesthetic agents into a new product. A new local recapture system (Anesthetic Recapture System; Anesthetic Gas Reclamation, Inc., Texas, USA) is also available and claims collection with reuse of 99% anaesthetic agent within the hospital. Full analyses of the carbon footprint produced by these systems have not yet been performed.
      Whilst none of the previously described techniques can be applied to nitrous oxide, mobile units are commercially available to catalytically convert it to oxygen and nitrogen (Excidio; Linde Group, Sweden). This type of technology can result in a six-to 17-fold reduction in CO2e (depending on energy source) (
      • Ek M.
      • Tjus K.
      Decreased emission of nitrous oxide from delivery wards - Case study in Sweden.
      ) and can also be used to collect halogenated anaesthetic agents (Anesclean; Showa Denko K.K., Japan) (
      • Yamauchi S.
      • Nishikawa K.
      • Tokue A.
      • et al.
      Removal of sevoflurane and nitrous oxide from waste anesthetic gases by using Anesclean®, the system for treating waste anesthetic gases.
      ). Widespread use of such technology could revolutionize anaesthetic agent procurement and emissions, particularly in larger hospitals.

      Injectable anaesthetic and analgesic drugs

      It is, of course, not just the inhalational agents used in anaesthesia which can have an environmental impact, but all of the pharmaceuticals used including ancillary agents such as cleaning products. The use of total intravenous anaesthesia may eliminate the GHG effect of volatile anaesthetic agents; however, there is an environmental cost as a result of their manufacture, transport, disposal and electricity consumption for their delivery. For instance, the carbon footprint of propofol use primarily stems from the energy required to operate the syringe pump (
      • Sherman J.
      • Le C.
      • Lamers V.
      • Eckelman M.
      Life cycle greenhouse gas emissions of anesthetic drugs.
      ). In addition, when calculating the impact of intravenous morphine preparations, the final stages (particularly sterilization and packaging) contributed to almost 90% of morphine’s carbon footprint (
      • McAlister S.
      • Ou Y.
      • Neff E.
      • et al.
      The environmental footprint of morphine: A life cycle assessment from opium poppy farming to the packaged drug.
      ). Incidentally, the same is not true of halogenated anaesthetic agents; the downstream CO2e of waste emissions of sevoflurane and isoflurane are eight and 33 times greater, respectively, than the GHG emissions, relating to manufacture, procurement and disposal of the agent (
      • Sherman J.
      • Le C.
      • Lamers V.
      • Eckelman M.
      Life cycle greenhouse gas emissions of anesthetic drugs.
      ). Wastage may increase the actual carbon emissions for injectable drugs; for instance, in two studies, it was shown that 32–51% of propofol in medical hospitals is wasted (
      • Gillerman R.G.
      • Browning R.A.
      Drug use inefficiency: A hidden source of wasted health care dollars.
      ,
      • Mankes R.F.
      Propofol wastage in anesthesia.
      ). Altered prescribing practices may, therefore, have significant carbon impacts; for example, prescribing only for the immediate need and replacing, if clinically appropriate, parenteral drugs such as non-steroidal anti-inflammatory drugs (due to the high energy costs of sterilization) with perioperative enteral drugs.
      There is a drive for standardization of calculating the total carbon footprint of pharmaceuticals and medical devices (
      Sustainable Development Unit
      GHG Protocol Product Life Cycle Accounting and Reporting Standard – summary.
      ), otherwise known as ‘cradle-to-grave’ or life-cycle analysis (LCA). For instance, using LCA, utilizing propofol to perform general anaesthesia creates nearly four times lower carbon emissions than desflurane or nitrous oxide (
      • Sherman J.
      • Le C.
      • Lamers V.
      • Eckelman M.
      Life cycle greenhouse gas emissions of anesthetic drugs.
      ). If LCA became mandatory for equipment and pharmaceuticals manufacturers, comparisons between carbon emissions of particular anaesthetic techniques could be made. The comparison of inhalational anaesthesia versus additional regional nerve blocks in veterinary anaesthesia remains to be determined. However, when LCA of medical hysterectomies was compared, the anaesthetic gases accounted for about 70% of the total surgical and anaesthetic carbon footprint (
      • Thiel C.L.
      • Eckelman M.
      • Guido R.
      • et al.
      Environmental impacts of surgical procedures: Life cycle assessment of hysterectomy in the United States.
      ), suggesting a potential role for intravenous and regional anaesthesia. Further research using the LCA approach is needed to holistically evaluate the benefit of alternative approaches to inhalational anaesthesia.

      Resource consumption and waste management

      Many easy sustainability goals can be met by simple changes to resource use and waste management, similar to changes which might be made in a domestic setting. High-priority resources to conserve include electricity, gas, oil, water and paper. Simple changes in the anaesthesia department are described in several review articles and might include turning off electronic equipment such as active anaesthetic scavenging systems, air conditioning or forced warm air machines when not in use, using alcohol-based scrubs or intermittent water flow devices for hand asepsis to reduce water consumption, redesigning sterile procedure kits to reduce wastage, and installing rechargeable batteries in portable equipment (
      • Kagoma Y.
      • Stall N.
      • Rubinstein E.
      • Naudie D.
      People, planet and profits: The case for greening operating rooms.
      ,
      • Sherman J.
      • McGain F.
      Environmental sustainability in anesthesia: pollution prevention and patient safety.
      ,
      • Axelrod D.
      • Bell C.
      • Feldman J.
      • et al.
      Greening the operating room and perioperative arena: environmental sustainability for anesthesia practice.
      ,
      • Wyssusek K.H.
      • Keys M.T.
      • van Zundert A.A.J.
      Operating room greening initiatives – the old, the new, and the way forward: A narrative review.
      ). New technologies such as low-flow scavenging interfaces (Dynamic Gas Scavenging System; Anesthetic Gas Reclamation, Inc.) may also provide significant energy savings (
      • Barwise J.A.
      • Lancaster L.J.
      • Michaels D.
      • et al.
      An initial evaluation of a novel anesthetic scavenging interface.
      ).
      In general, the more hazardous or infectious the waste, the more expensive and polluting are the disposal methods. The waste hierarchy (Fig. 1) is a useful concept introduced in 1975 by the EU in order to optimize waste management. A legal duty of care was placed on business and public bodies to prevent waste and waste residue disposal where possible by moving up the waste hierarchy ladder. Following the waste hierarchy, by improving waste segregation, is likely to provide significant financial savings; clinical waste streams can have disposal costs 10 times those of recycling waste streams. Systematic application of these principles in the medical environment is reported using the five Rs of waste management: reducing, reusing, recycling, rethinking and researching (
      • Kagoma Y.
      • Stall N.
      • Rubinstein E.
      • Naudie D.
      People, planet and profits: The case for greening operating rooms.
      ).
      Figure 1
      Figure 1The Waste Hierarchy (adapted from
      Department for Environment, Food and Rural Affairs
      Applying the Waste Hierarchy: evidence summary.
      )
      The priority is to avoid initial use of resources where possible, and this is best achieved by the audit of current practices within organizations. Around 60% of the carbon footprint of a hospital is likely to result from procurement of materials and equipment (
      Sustainable Development Unit
      Carbon Footprint update for NHS in England 2015.
      ); therefore, incorporating sustainability into procurement planning is essential and suggestions to achieve this in the veterinary clinic are outlined in Table 2. In medical anaesthesia, there is great pressure to avoid reuse of medical devices such as anaesthetic breathing systems, face-masks, laryngoscopes and catheters to facilitate infection control (
      Association of Anaesthetists of Great Britain & Ireland
      Infection control in anaesthesia.
      ). Development of greater understanding regarding the risks of infection, methods of decontamination, new methods of recycling of contaminated single-use equipment and full LCAs for medical devices (including costs of sterilization) will inform these decisions to reduce the dilemma. Given that new electricity in the UK/EU is principally sourced from renewable sources rather than fossil fuels, converting to reusable rather than single-use equipment in a five-theatre medical hospital was estimated to result in 84% reduction in CO2 emissions and an annual saving of around £18,000, although water use was doubled (
      • McGain F.
      • Story D.
      • Lim T.
      • McAlister S.
      Financial and environmental costs of reusable and single-use anaesthetic equipment.
      ). Reusable surgical textiles can offer significant improvements in carbon emissions and resource usage (
      • Overcash M.
      A comparison of reusable and disposable perioperative textiles: Sustainability state-of-the-art 2012.
      ) and may improve infection control (
      • Markel T.A.
      • Gormley T.
      • Greeley D.
      • et al.
      Hats off: a study of different operating room headgear assessed by environmental quality indicators.
      ). However, world water shortages are predicted which may adjust the balance of calculations in the future (
      • Mancosu N.
      • Snyder R.L.
      • Kyriakakis G.
      • Spano D.
      Water scarcity and future challenges for food production.
      ).
      Table 2Example of a sustainable procurement policy
      AreaExamples and resources
      Evidence from suppliers of environmental policies or accreditations
      • Accreditation standards include:
      • ISO 14001 (International Organization for Standardization: Environmental Management)
      • EMAS (European Union Eco-management and Audit Scheme)
      • The Carbon Trust
      • Investors in the Environment (UK only)
      • Green Guide for Healthcare (self-certifying)
      Environmental legislation and compliance, management and impactsEnvironmental management schemes; environmental policies; waste certificates; duty-of-care visits; carbon life-cycle impacts; supporting local businesses; zero-to-landfill policies
      EnergySourcing renewable energy; divesting from fossil fuels
      PackagingRequesting recyclable, reusable, biodegradable and minimal packaging
      Transport costsReducing number and distance of journeys; consolidating deliveries; teleconferencing
      Product choiceAvoidance of environmentally toxic products; energy efficient equipment; healthier and sustainable foods
      Stock controlStock so that supply is sufficient but items do not go out-of-date; reuse or recycle before reordering
      Ethical procurementKnowledge of supply chain to protect labour standards; source Fair Trade products; follow ethical procurement guidelines ()
      Water managementEmploy water-saving devices; avoid bottled water; ‘grey’ water facilities; drought-resistant planting
      Plastic waste disposal is a topical issue in many countries. Plastic manufacture and disposal are energy-demanding processes, and incineration of medical plastics is a leading cause of harmful toxic emissions such as dioxins (
      • Windfeld E.S.
      • Brooks M.S.L.
      Medical waste management - A review.
      ). Over 40% of disposable medical devices are made of polyvinyl chloride (PVC), which is cheap and durable. However, health concerns regarding high dioxin emissions and the phthalate plasticisers such as diethylhexyl phthalate (DEHP) used to soften PVC (
      • Windfeld E.S.
      • Brooks M.S.L.
      Medical waste management - A review.
      ,
      • Benjamin S.
      • Masai E.
      • Kamimura N.
      • et al.
      Phthalates impact human health: Epidemiological evidences and plausible mechanism of action.
      ) have resulted in many manufacturers producing PVC-free and DEHP-free products (
      • Conway K.
      List of Medical Products that Meet the HH PVC and DEHP Elimination Goal.
      ).
      Disposal of pharmaceutical agents is strictly controlled in most countries, and drug-contaminated waste is often disposed by expensive incineration. Without incineration, volatile anaesthetic agents absorbed into charcoal canisters could be released into the atmosphere. However, drug contamination of water and soil is a recognized problem as many drugs are only partially removed by waste water treatment (
      • Fatta-Kassinos D.
      • Meric S.
      • Nikolaou A.
      Pharmaceutical residues in environmental waters and wastewater: Current state of knowledge and future research.
      ). This may be problematic for drugs which, like propofol, persist and are toxic in the aquatic environment (
      • Mankes R.F.
      Propofol wastage in anesthesia.
      ); however, the environmental risk of propofol has been categorized as low (
      • Stockholm County Council
      Environmentally Classified Pharmaceuticals 2014-15.
      ). In the UK, body fluids containing drug residues and metabolites by patients receiving therapeutic pharmaceuticals do not normally class as medical waste unless cytotoxic or cytostatic drugs are used and potentially dangerous quantities of unmetabolized drugs are likely to be present in the waste (
      • Department of Health
      Health Technical Memorandum 07-01: Safe management of healthcare waste.
      ). Most countries require an environmental risk assessment to be performed by the manufacturer during drug licensing. No unifying toxicity index exists, but there is guidance produced by the European Medicines Agency, under current review, on investigation and labelling of the environmental risk of medicinal products which includes indexing based on persistence, bioaccumulation and toxicity of drugs (
      European Medicines Agency
      Concept paper on the revision of the ’Guideline on the environmental risk assessment of medicinal products for human use’.
      ), in addition to an existing index produced in Sweden (
      • Stockholm County Council
      Environmentally Classified Pharmaceuticals 2014-15.
      ). These indices should be considered when considering the ecological risk of drugs which may escape safe disposal methods.
      In the USA, around one-third of the waste generated in hospitals originates in the operating room (
      • Chung J.
      • Meltzer D.
      Estimate of the carbon footprint of the US Health Care Sector.
      ), and it is estimated that 40–58% of medical anaesthetic waste can be recycled (
      • McGain F.
      • Hendel S.A.
      • Story D.A.
      An audit of potentially recyclable waste from anaesthetic practice.
      ,
      • Shelton C.L.
      • Abou-Samra M.
      • Rothwell M.P.
      Recycling glass and metal in the anaesthetic room.
      ). Recycling options for many single-use items have historically been limited, with most waste deemed infectious or drug-contaminated and disposed of according to the legal requirement of the country, usually by alternative treatment (disinfection) or incineration, respectively. Recently, the UK’s Environmental Agency has granted a permit for contaminated medical-grade PVC to be recycled into tree ties. Using recycled PVC reduces the energy for production by 85%, and this scheme has been adopted in Australia and the UK (
      • Vorster T.
      Plastic recycling from the operating theatres, working towards a circular economy.
      ). Unfortunately, this scheme is not currently available to UK veterinary producers due to the limitations of the environmental permit.
      Such new recycling and refuse-derived energy industries are developing to support a circular economy, redefining products and services to design waste out, and these are likely to be cost-saving for organizations (
      • Goldberg M.E.
      • Vekeman D.
      • Torjman M.C.
      • et al.
      Medical waste in the environment: Do anesthesia personnel have a role to play?.
      ). Additional innovations will reduce the need for incineration of plastic containers such as reusable sharps containers (Sharpsmart Reusable Container System; Sharpsmart, UK; Stericycle Bio Systems; Stericycle, UK) and cardboard pharmaceuticals waste containers (Bio-bin; Econix Ltd, UK; Clinisafe Cardboard Cartons; Frontier Medical Group, UK; 4GSafe Boxes; Icomed Ltd, UK).
      It is essential that each organization has a strategy to ensure that waste and waste residues generated are removed from incineration or landfill streams. Waste can be segregated at source into reuse, recycling, autoclave sterilization or refuse-derived energy streams, within national legal frameworks. Many waste companies offer ‘zero-to-landfill’ schemes. To assist in identifying the most sustainable options for each type of waste, a scientific summary of the environmental impact of various non-medical waste management options has been produced by the UK government (
      Department for Environment, Food and Rural Affairs
      Applying the Waste Hierarchy: evidence summary.
      ). One pragmatic problem is how to categorize medical waste to optimize financial and environmental costs (
      • Windfeld E.S.
      • Brooks M.S.L.
      Medical waste management - A review.
      ); is the waste contaminated with noninfectious or infectious and pathogenic bodily secretions? Guidance is likely to be available from national regulatory organizations and must be communicated clearly to staff.

      Engagement in sustainability

      Many organizations now have environmental management schemes and corporate social responsibility (CSR) programmes, which aim to increase the positive impacts and reduce the negative impacts, relating to company activities. CSR policies usually include procurement, travel and transport plans, and community and staff engagement. Careful thought must be given to overcoming potential barriers to change, which can include social attitudes and logistic, institutional and legal restrictions (
      • Hutchins D.C.J.
      • White S.M.
      Coming round to recycling.
      ).
      The sustainability movement in medicine has made great progress in the past decade. Alone, the NHS’s activities contribute 3% of the UK’s national carbon emissions, but it has committed to an 80% reduction carbon emissions from the health and care systems by 2050 (). There are various global medical healthcare initiatives which are driving sustainability via leadership, policy statements, research funding and education; a nonexhaustive list includes Healthcare Without Harm, the NHS’s Sustainable Development Unit, the UK Health Alliance on Climate Change and the Centre for Sustainable Healthcare. In addition, there are environmental groups within the Royal College of Anaesthetists, the American Veterinary Medical Association, the Société Francaise d’Anesthésie et de Réanimation, The Australian and New Zealand College of Anaesthetists and Association of Anaesthetists. The latter has produced a newsletter which gives an engaging summary of activities of UK medical anaesthetists, including research awards, ‘greening’ the headquarters and promoting sustainable conferencing with no conference bags, careful choice of location and venues, teleconferencing and meat-free days (
      Association of Anaesthetists of Great Britain & Ireland
      Anaesthesia News May 2018: The Newsletter of the Association of Anaesthetists of Great Britain and Ireland.
      ).

      Future directions for sustainable veterinary anaesthesia

      Currently, there is little cohesive focus within the veterinary professions to direct sustainability initiatives. A clinical checklist has been produced by the American Society of Anesthesiologists (
      • Axelrod D.
      • Bell C.
      • Feldman J.
      • et al.
      Greening the operating room and perioperative arena: environmental sustainability for anesthesia practice.
      ) which can be used to guide sustainable anaesthetic practices within institutions (reproduced in modified format in Table 3). More resources are becoming available, such as the UK’s National Institute for Health Research framework to minimize waste by improving research design (), and metrics to identify health benefit per tonne CO2e may become a standard part of research reporting. Engagement with the research community to promote sustainability principles in research anaesthesia is encouraged. Lastly, environmental awareness is slowly being introduced into medical and veterinary curriculums, often under the cover of the more collaborative One Health initiative (
      • Nielsen N.O.
      • Eyre P.
      Tailoring veterinary medicine for the future by emphasizing one health.
      ,
      • Walpole S.C.
      • Vyas A.
      • Maxwell J.
      • et al.
      Building an environmentally accountable medical curriculum through international collaboration.
      ,
      • Waters A.
      Progress report - One Health.
      ). Suggested medical learning objectives for sustainability are 1) to be able to describe the interactions between the environment and human health, 2) to demonstrate the ability to improve sustainability in health care and 3) to address the wider ethical and legal dimensions of sustainability relating to geographically divergent and future populations (
      • Walpole S.C.
      • Pearson D.
      • Coad J.
      • Barna S.
      What do tomorrow’s doctors need to learn about ecosystems?–a BEME systematic review: BEME guide no. 36.
      ).
      Table 3An anaesthesia sustainability checklist
      Based on ‘Appendix B: Anesthesiology Sustainability Checklist’ (Axelrod et al. 2017). A copy of the full text can be obtained from the American Society of Anesthesiologists or online at www.asahq.org/∼/media/sites/asahq/files/public/resources/asa%20committees/greening-the-or.pdf?la=en Last accessed 7 March 2019.
      Reduce volatile anaesthetic atmospheric wasteLow fresh gas flows

      Monitoring of inspired oxygen and end-tidal anaesthetic agent concentrations

      Avoid high-impact agents (desflurane, nitrous oxide)

      Consider intravenous and regional techniques

      Invest in waste anaesthetic recycling or destruction
      Reduce pharmaceutical wasteUse prefilled syringes or pre-packed kits

      Use appropriate sized vials

      Dispose of pharmaceuticals appropriately

      Replace perioperative injectable with oral medications
      Reduce equipment wasteOnly open equipment intended for immediate use

      Purchase reusable or reprocessed equipment

      Adjust stock levels to minimize discard beyond expiry dates; eliminate unnecessary items
      Waste segregationEvaluate waste handling to move up the waste hierarchy

      Segregate waste strictly, according to legal frameworks

      Recycle where possible, in clinical and nonclinical streams

      Use reusable or nonplastic waste containers

      Minimize packaging
      TextilesUse reusable textiles

      Use towels and blankets efficiently
      ElectronicsDo not use unless proven benefit

      Use certified recycling site for disposal
      LeadershipDevelop a sustainability plan and committee, with advocates at local level

      Procure sustainably where possible

      Promote staff engagement with sustainability

      Evaluate travel within your organization

      Promote research into sustainability
      Based on ‘Appendix B: Anesthesiology Sustainability Checklist’ (
      • Axelrod D.
      • Bell C.
      • Feldman J.
      • et al.
      Greening the operating room and perioperative arena: environmental sustainability for anesthesia practice.
      ). A copy of the full text can be obtained from the American Society of Anesthesiologists or online at www.asahq.org/∼/media/sites/asahq/files/public/resources/asa%20committees/greening-the-or.pdf?la=en Last accessed 7 March 2019.
      At present, Elsevier prints Veterinary Anaesthesia and Analgesia in the USA on sustainably sourced paper (as certified by the Publishers’ Database for Responsible Environmental Paper Sourcing) and delivers copies worldwide in recyclable plastic wrapping (De Koning, personal communication 2018). However, Veterinary Anaesthesia and Analgesia is also available online with an ever-extending range of online content. Globally, information and communication technology produces an estimated 1.4% of total global carbon emissions (
      • Malmodin J.
      • Lundén D.
      The energy and carbon footprint of the global ICT and E & M sectors 2010-2015.
      ). Whether there is an environmental advantage of reading a journal article online will depend on the lifetime of the device used, energy efficiency of the device, reading time and number of readers; one study estimated casual reading of academic articles on electronic devices to be more environmentally friendly than reading paper copies (
      • Song G.
      • Che L.
      • Zhang S.
      Carbon footprint of a scientific publication: A case study at Dalian University of Technology, China.
      ).
      It is clear that there will be a growing need for carbon and climate literacy in both the veterinary clinical and research fields. It remains for veterinary anaesthetists, both as professionals and individuals, to decide how we will integrate sustainable practices into veterinary anaesthesia. In the future, it seems likely that carbon reduction commitments and sustainability plans will be required from all businesses and public bodies, and creation of these environmental management systems will make organizations more resilient. Understanding the greenhouse gas effects of inhalational agents can proceed along with further development of low flow anaesthesia and consensus on the use of nitrous oxide and desflurane in clinical practice. Inclusion of sustainability topics into undergraduate and specialist curriculums may promote further research into life-cycle analyses of anaesthetic equipment and procedures and eventually better understanding of the environmental cost of veterinary healthcare across clinical and research fields. Educational conferences can be planned to reduce both the carbon footprint and environmental impact. We encourage veterinary anaesthetists to engage with sustainability and provide leadership within their own spheres.

      Authors’ contributions

      RSJ and EW: conception, preparing and revising of manuscript.

      Conflict of interest statement

      Authors declare no conflict of interest.

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