High-Impact Actions to Reduce the Carbon Dioxide Footprint in an Ophthalmic Operation Room: A Narrative Review

Climate change is impacting human lives and health. According to the World Health Organization, climate change is expected to cause approximately 250,000 additional deaths per year between 2030 and 2050 [1]. Germany’s health care footprint accounts for 5.2% of the national emissions footprint which results in 0.71 tons of CO₂ emission per capita [2]. Thus, the health sector has a responsibility to take climate action. Large parts of the emissions generated by health care have indirect sources or are embodied in upstream manufacturing of products and energy that support health care facilities [3]. In that context, anesthesiology and the use of volatile anesthetics (VAs) have a major role to play. The carbon dioxide equivalent emissions for general anesthesia account on average for 14.9 (95% CI, 9.7–22.5) kg [4].

Surgery is a resource-intensive health care activity, requiring expensive equipment, sterilization procedures, advanced operative technologies, and obligatory life support systems. These activities use considerable amounts of energy and consumables and generate copious waste volumes [5].

We spotlight on the situation in a department of ophthalmology with frequent anesthesia services and highly standardized procedures. Ophthalmology in general has the highest procedural volumes of any specialty. For the evaluation and comparison of the resource consumption in the ophthalmic operating room, we centered our interest on the world’s most common surgical procedure, i.e., the cataract surgery with annually approx. 800,000 procedures in Germany [6].

Here, we focus on high-impact actions which result in a major reduction of the CO₂ footprint according to the global road map for health care decarbonization [2]. We aim at making the health care service greener (Fig. 1).

• 1.

  Reduce unnecessary pharmaceutical use, substitute high emissions products with more climate-friendly alternatives, and incentivize the production of affordable green, climate-smart medicine.

• 2.

  Work on the limitations and demand transparency of raw material source and life cycle assessment from the companies.

• 3.

  Implement circular health care and sustainable health care waste management. Implement circular economy principles to procure supplies, deploy clean technologies, reduce the volume and toxicity of health care waste, and manage waste sustainably.

• 4.

  Establish greater health system effectiveness. Reduce emissions by improving system effectiveness, including eliminating inefficient and unnecessary practices, linking carbon reduction and quality of care, and bolstering resilience.

The biggest part of waste in cataract surgery is general waste, followed by cardboard, glass, and plastics [7]. Analysis in phacoemulsification showed that about 47% of the waste volume after cataract surgery is due to solid raw materials such as gloves, covering material, and phacoemulsification cassettes, and 53% is based on liquids. About 50% of the waste was rated as reusable, including cardboard and glass, which can be recycled. However, the other half was rated as non-recyclable, for example, plastic packaging for transport of intraocular lenses. Measurements of plastic packaging weights revealed that packaging differs by up to 300% [7]. In this aspect, the ophthalmologist should control the purchase and adopt the strategy of buying an equivalent but less elaborately packaged implant.

Nevertheless, recycling is not as easy in an environment that is ruled by strict hygiene regulations. Once a patient contact occurs, a product is considered contaminated. This limits reuse and a costly reprocessing or requires incineration. Wrong deposition of items can be problematic too and a waste separation system should be clearly defined and communicated.

Another delicate problem is the question whether disposable instruments are of advantage compared to reusable instruments. Problems such as use-related defects and mistakes in instrument composition in the sterilization process can be avoided using disposable instruments. Even if this aspect is negligible in cataract surgery as the quantities of packaging are much more relevant, the not inconsiderable energy consumption in the production of each instrument has to be taken into account. For a valid assessment, the knowledge about the resources and the product life cycle according to ISO 14040 of ophthalmic surgical reusable and disposable instruments is required before a clear recommendation can be made. Another suggestion for saving resources is the planning and coordination of material orders in order to reduce packaging and shipping waste.

Disposable items are ubiquitous in anesthesia and are increasingly displacing reusable products. The main influencing factors in the decision process between single-use and reusable products are quoted as concern for hygiene, convenience, and cost, while environmental factors have traditionally played a smaller role [8].

One obvious problem which needs to be considered to reduce waste and environmental damage is the discard of drugs. Smaller vials should be used to reduce the volume of waste. In the year 2000, a study revealed that various anesthetic drugs were used inefficiently and accounted for an avoidable amount of waste. For example, up to 20% of propofol waste is considered to be avoidable [9]. We propose to use either TCI-controlled anesthesia induction using large vials with a volume of 50 mL for anesthesia induction and maintenance or to use 20 mL propofol vials and inject the whole volume fractionated prior to starting the propofol syringe pump. In addition to the environmental damage, this process is of economic advantage. Wasted drugs make up for approximately one quarter of the total cost of drugs [10].

The goals of anesthesia during ophthalmic surgery focuses on patient safety and providing analgesia to elicit a pain-free experience and create optimal surgical conditions to facilitate the procedure in collaboration with the surgical staff, including the ophthalmic surgeons and theater nurses [11]. The inclusion of topical and regional anesthesia has improved the anesthetic techniques which can be used to facilitate ophthalmic surgeries while providing excellent patient care [12]. However, general anesthesia continues to be important, especially in the case of children [13], reduced compliance, and difficult surgical conditions as well as in patients with cognitive decline and diseases such as Parkinson disease and dementia [14]. During general anesthesia for ophthalmic surgery, a deep plane of anesthesia is maintained to avoid laryngospasm, coughing, or other movement that may cause direct eye injury and/or increase intraocular pressure [15]. This increases the demand of anesthetic drugs and draws attention to the environmental impact of anesthesia in eye surgery.

For general anesthesia, VAs are the most commonly used agents. VAs and nitrous oxide exhibit potent greenhouse effects when released into the atmosphere. With regard to the global warming potential (GWP) also the ophthalmic surgery is affected as three intraocular gases are currently in use in vitreoretinal surgery as endotamponades, i.e., sulfur hexafluoride (SF₆), hexafluoroethane (C₂F₆), and perfluoropropane (C₃F₈). As these represent contributors to the greenhouse effect and global warming, every effort should be undertaken to reduce their usage and impact.

Modern VAs include the hydrofluorocarbons sevoflurane and desflurane and the chlorofluorocarbon isoflurane. These undergo minimal in vivo metabolism and are released virtually unchanged (≥95%) into the troposphere, which is the lowest layer of the atmosphere in which the greenhouse gas (GHG) effect occurs [16]. Desflurane is known to remain in the troposphere for 14 years, while in contrast, sevoflurane remains in the troposphere for only 1.4 years [17]. In Germany, inhaled anesthetics were used in around 7 million operations, with the proportions of sevoflurane accounting for around 55%, desflurane around 35%, and isoflurane around 10% in 2012 [18]. A key contributor to climate change is the emission ofGHGs which includes release of waste anesthetic gases from surgical procedures into the environment. The largest life cycle GHG among anesthetic drugs is desflurane. GHG impact of propofol in contrast are comparatively small, nearly 4 orders of magnitude lower than those of desflurane or nitrous oxide [19]. According to a study of Shermann and colleagues, in contrast to VAs, the GHG impacts of propofol primarily results from the electricity required for the syringe pump and not from drug production or direct release to the environment [17]. If the use of VAs is required, care should be taken to ensure that the fresh gas flow is as low as possible. High fresh gas flow increases the effect of all volatile agents on the environment by releasing greater quantities into the atmosphere. VAs, especially sevoflurane and desflurane, are potent GHGs which carry significant GWP by trapping heat. Desflurane carries 2,540 times the GWP of carbon dioxide (CO₂) over 100 years (GWP100) whereas sevoflurane exceeds the effect of CO₂ by only 130 times. Studies demonstrated that avoiding the use of desflurane could obviate 67% of emissions attributable to an anesthesia department [20].

Thus, we recommend the implementation of propofol-based techniques for general anesthesia to avoid direct GHG emissions. However, this should take into account the indirect carbon footprint of propofol such as the environmental impact of drug manufacturing, packaging, transportation, the need for single-use plastics, the drug delivery system, and drug waste and disposal. Of special interest in the context of propofol is the traceability of the sourcing of propofol constituents, 10% of which is soybean oil [21]. The environmental impact of soy cultivation in tropical regions extends to lost habitat, carbon emissions from forest clearing, and water and agrochemical demands. By demanding greater transparency from pharmaceutical companies, we can make better informed decisions and encourage sustainable production practices. The same considerations should also be made when selecting the appropriate opiates [22].

Pediatric cataract surgery is relatively rare in children in the developed countries. However, it is of high importance as it is able to provide lifelong improvement of visual impairment [23]. Pediatric patients are a high-risk group regarding perioperative hypothermia (especially after general anesthesia) because of the less effective regulatory capacity of the central nervous system on body temperature, asymmetrical body weight/surface area, and lower levels of subcutaneous fatty tissue [24]. Postoperative hypothermia can cause various adverse effects, such as wound infections and cardiac arrhythmia [25]. Instead of heating the operating room, we recommend the use of a forced-air warming system to keep the children’s body temperature adequate during the whole operative period. The opportunity to stick to the standard operating room ambient temperature (20–23°C) [26] prevents unnecessary heating of the whole room and maintains staff comfort. Temperature control and local warming helps saving energy resources.

Recently published data revealed that transportation of goods and patients contributes to 2.3 Mt of carbon dioxide equivalent (CO₂e) to the total global environmental impact of health care [27]. In England, for example, travel was considered as a carbon “hotspot,” causing 13% of the NHS in England’s carbon footprint [28]. To this end, it is necessary to review the need for staff, patient and visitor travel, and to promote the use of telemedicine. Patient visits to the hospital must be as coordinated as possible to reduce traveling and to combine examination appointments.

The advantages of telemedicine should be implemented in the clinical routine as many studies have shown the improvement in patient satisfaction secondary to ease of use, decreased travel time, decreased wait times, as well as improved outcomes from telemedicine [27].

Employees are increasingly expecting – and putting pressure on employers to provide – recycling facilities in the workplace. Statistics indicate for Australia that 80% of employees would like more recycling in the workplace and that having recycling facilities makes them feel that they work for a responsible employer [29]. The offer to contribute to a structured waste avoidance and recycling system meets a high moral need of many employees in the health care sector and could represent a motivational impulse in everyday life. This aspect is of additional interest as building communities among clinicians and other members of the health care workforce can help promoting resilience and avoiding burnout [30].

In this review, we have summarized how the CO₂ footprint can be reduced in an ophthalmic operating room. The focus herein is on topics such as the strength of employee empowerment and the introduction of sustainability as an important criterion in material procurement. Taking practical steps to reduce the environmental impact on anesthesia and surgery practices are relatively simple but effective and yield relevant co-benefits.

The authors have no conflicts of interest to declare.

The authors received no financial support for the research, authorship, and publication of this article.

The authors confirm contribution to the paper as follows: study conception and design: C.K. Weisheit, F.G. Holz, and M. Coburn; literature collection: C.K. Weisheit, M Coburn, G. Geerling, and F.G. Holz; draft manuscript preparation: C.K. Weisheit and M. Coburn. All authors reviewed the results and approved the final version of the manuscript.