The environmental impact of veterinary anaesthesia is an increasingly important topic. Some people appear to think that hospitals should ‘get a free pass’ to pollute because of the importance of the job (Rasheed and Walraven, 2023); however, in recent years demand is being placed on healthcare organisations to mitigate and adapt to climate change (Jones and West, 2019). Veterinary professionals have expressed interest in learning new ways to reduce their environmental impact and improve sustainability in veterinary clinics and hospitals (Koytcheva et al, 2021). Propofol is claimed to be the most widely dispensed and wasted drug in both human and veterinary anaesthesia. Reportedly as much as 32–49% of all propofol is wasted (Petre and Malherbe, 2020). Propofol is routinely administered to effect for induction of anaesthesia. This means that the amount drawn up is often not fully administered to the patient and will end up going to waste. This article highlights not only the amount of wastage that is occurring daily in veterinary hospitals by looking at the results of an audit but emphasises the wider implications: from the production of the drug using raw materials to the further reaching consequences wastage has on our environment.
Method
A labelled box was placed in the hospital prep room and all staff were asked to dispose of any waste propofol syringes into the box once they had finished their anaesthetic and handed their patient back to the wards for recovery. Syringes were collected for a period of 1 week from the surgery department only. A collection period of 1 week was selected because of time constraints and staff compliance.
Results
In total, 33 patients underwent surgery during the week of data collection. Twenty syringes containing a total of 88.530 ml propofol were collected in the box provided (Figure 1). By multiplying the total waste by 52 weeks, a rough estimate was calculated of 4602 ml (229.84 × 20 ml vials) of propofol wasted each year in the surgery department of the hospital. Each pack of 5 × 20 ml vials costs the hospital £32.08 +VAT, giving an estimated loss of £1475.57 +VAT each year in propofol wastage (Table 1). However, it should be noted that 13 syringes were not accounted for during the process of data collection, so actual total figures are likely to be higher.
Table 1. Actual product and financial wastage over a 1-week period in the surgery department of a referral hospital and estimated annual wastage
| Actual data collected during 1 week | Estimated total for the year (totals × 52 weeks) | |
|---|---|---|
| Number of cases that had surgery | 33 | 1716 |
| Number of syringes placed in the box | 20 | – |
| Number of syringes unaccounted for | 13 | – |
| Amount of propofol wasted | 88.5 ml | 4602 ml |
| Average amount per syringe | 4.42 ml | – |
| Amount of vials wasted in 20ml vials | 4.42 vials | 229.84 vials |
| Cost to practice (£) propofol only. (one box of 5 × 20 ml vials costs £32.08 + VAT) | £28.38 + VAT | £1475.57 + VAT |
Note that 13 syringes were missing so the actual figures may be higher
Discussion
Unfortunately, there were some limitations to data collection. To ensure that people kept their leftover syringe they had to be made aware that these were being collected. This may have led to people drawing up less propofol at the start of their case to reduce wastage. Additionally, 13 out of 33 syringes went missing. This is a 39.39% data loss, so a lot of assumptions had to be made about the missing syringes, making data highly inaccurate. The hospital has a highly variable case load week-to-week, and it was a quiet week in the lead up to Christmas, so not as many surgeries as usual were carried out. Audits carried out at human hospitals across the globe found that between 32 and 51% of all propofol dispensed in hospitals went to waste (Sherman et al, 2012).
Waste management
All waste pharmaceuticals need to be treated properly. Any syringes with propofol left in them should be discarded into disposal of old pharmaceutical bins to be collected for disposal by an authorised company. The collection, treatment and disposal of this waste can lead to contamination of the environment (Cook et al, 2012). Unmetabolised propofol does not degrade in the environment, is highly mobile in soil, accumulates in fat (Petre and Malherbe, 2020) and is toxic to aquatic life (Tang et al, 2023). The recommended route of disposal is incineration (Tang et al, 2023). However, as well as oxidising active pharmaceutical ingredients, incineration produces air emissions and ash (Cook et al, 2012). Even when the pharmaceuticals are correctly sent for incineration, it is possible that some unprocessed propofol could end up in the environment as a result of accidents or improper waste handling (Sherman et al, 2012).
Propofol arrives at the hospital in glass vials housed in cardboard packaging (Figure 2). Waste segregation is extremely important to help reduce both the environmental contamination and financial impact of waste disposal. Anaesthetists across the globe reported a lack of information, lack of recycling facilities, negative staff attitudes and inadequate leadership as reasons for reduced recycling within hospitals (Ard et al, 2016). Staff education and placing pictograms (Figure 3) on bins can help improve the proper segregation of waste items. Likewise implementing the five R's of waste management – reducing, reusing, recycling, rethinking and researching – can lessen our impact on the planet.
Water contamination
Studies have found toxic effects of propofol on a wide range of species including not only freshwater fish but also crustaceans and algae (Allen et al, 2021). There is no evidence of biodegradability in water (Hu et al, 2021). Based on a model pond experiment taking into consideration adsorption into solids in the water, the volatilisation half-life was found to be 6.5 years (National Center for Biotechnology Information, 2020). According to the Association of Anaesthetists, propofol has been detected not only in our waterways but also in our drinking water, in the tissues of fish and even in emissions from textile floor coverings (Allen et al, 2021).
Carbon footprint and greenhouse gases
Greenhouse gases and vapours absorb and reflect outgoing radiation from the earth's lower atmosphere, effectively trapping the radiation and causing an increase in surface temperature across the globe. This increased temperature is linked to an increase in diseases, heat waves, droughts, malnutrition, flooding of coastal areas and decreased water availability elsewhere, ultimately resulting in loss of ecosystems, habitats and species (Jones and West, 2019).
Common greenhouse gases associated with veterinary anaesthesia include carbon dioxide, methane, nitrous oxide, water and all halogenated anaesthetic agents. The use of propofol total intravenous anaesthesia as a replacement is suggested to reduce the greenhouse gases produced during the anaesthetic process. However, it is important to consider the environmental impact of the manufacturing process, transport, disposal of and electricity used to operate the syringe driver (Jones and West, 2019). The carbon footprint of a drug is defined by the total amount of greenhouse gases emitted in the manufacture, transportation, use and disposal of the final product (Jones and West, 2019). Compared to other anaesthetic drugs, including volatile agents, propofol has a minimal carbon footprint when disposed of properly. The majority of active pharmaceuticals entering the environment come from human and animal excretion (Cook et al, 2012). Only 1% of propofol is excreted unchanged in the patient's urine, the rest is metabolised by the body (Hu et al, 2021). The life cycle of greenhouse gas emissions produced by the use of propofol are much lower than that of inhalational anaesthetic agents (Tang et al, 2023). It is also reported that propofol has a relatively low global warming potential compared to 20 other commonly used injectable anaesthetic drugs (Lane, 2020).
Production and raw materials
It is important to also consider the environmental impact of the production of the drug. Pharmaceutical manufacturing is well documented in association with waste water contamination and greater waste increases demand for production (Tang et al, 2023). Propofol is composed of soy bean oil, eggs, phenols, ethanol, glycerol and water (Table 2). All these components must be sourced and transported, contributing to the overall environmental impact of the drug (Tang et al, 2023). Manufacturing plants may also contribute to environmental contamination, but there are no reliable estimates as to how much (Sherman et al, 2012).
Table 2. The raw ingredients used to manufacture 1 kg of propofol
| Consumable | Volume |
|---|---|
| Phenol | 0.02 kg |
| Isopropyl alcohol | 0.08 kg |
| Soybean oil | 0.1 kg |
| Eggs | 0.996 kg |
| Benzyl alcohol | 0.0015 kg |
| Glycerol | 0.0225 kg |
| Ethanol extraction | 0.996 kg |
| Water | 0.85 kg |
| Electricity | 10.2820 kwh |
Soy
The cultivation of soy has been linked with intensified deforestation within the Amazon basin. This impact extends to loss of habitat, increased carbon emissions from forest clearing and increased water demands (Sherman et al, 2012). Many propofol manufacturers claim to use only sustainably sourced soybean derivatives; however, many do not disclose their sources for confidentiality reasons (Lane, 2020).
Eggs
Last year it was estimated that seven million tons of eggs were produced in the EU (Guillaume et al, 2022). While the production of eggs for medicines will be minimal compared to those produced for food, the intensive production of eggs across the globe consumes electricity for ventilation, lighting and feeding, gas for heating and incineration of dead birds, fuel for transport and feed for the birds. It also creates manure which leaks ammonia and nitrates into the environment (Leinonen et al, 2012).
Associated waste products
Waste segregation is extremely important to help reduce both the environmental contamination and financial impact of waste disposal. Reduction of the waste produced is the most impactful change we can make, including wasting less product, making choices to purchase products that contain less packaging and sourcing reusable alternatives to single use items (Koytcheva et al, 2021).
Plastics in syringes and needles
Waste plastic is also an issue related to propofol wastage. The manufacture and disposal of plastics uses a lot of energy and the disposal of plastics via incineration in pharmaceutical waste releases toxic emissions into the environment (Jones and West, 2019). As well as being produced from fossil fuels, plastics are associated with vector-borne diseases, leak toxins into water ways, suffocate wildlife and clog sewage systems. There is a trend in human medicine for glass syringes as a replacement when used for repeated personal use (Rasheed and Walraven, 2023). While we cannot reuse syringes or share them between patients, it might be beneficial to focus on the wrapping that the syringes are sterilised in rather than the syringes themselves. Most syringes and needles are wrapped in a plastic film with a paper backing. Requesting all-paper packaging from manufacturers or bio-degradable alternatives would reduce the amount of plastic going to landfill from the hospital (Figure 4) (Rasheed and Walraven 2023). Veterinary professionals can also focus on reduction, by calculating drug doses and thus avoiding unnecessary drug preparation (Lane, 2020).
Transportation
Transportation of products inevitably creates carbon emissions (Koytcheva et al, 2021). To reduce this, practices can make a conscious effort to have fewer deliveries. Many practices have limited their stock orders to a larger once or twice a week delivery, rather than having a small amount of stock delivered daily, in an attempt to reduce their overall carbon footprint.
Financial implications
Wastage of any kind can put a strain on the finances of a veterinary hospital. A study carried out in human hospitals found that propofol was a major contributor to financial waste; however, the authors also mentioned that faster recoveries could save money in other areas of the hospital (Kaniyil et al, 2017). Faster recoveries post-propofol targetcontrolled infusion compared to those maintained with volatile agents, may reduce man hours spent recovering patients, use of monitoring equipment during recovery, use of oxygen during the recovery period and any drugs that might be used to antagonise slow recoveries, all reducing overall costs to the hospital.
Waste segregation is extremely important to help reduce both the environmental contamination and financial impact of waste disposal. It is reported that clinical waste disposal can be up to ten times more expensive than recycling systems (Jones and West, 2019). All staff working in practice should undergo appropriate waste-disposal training (Koytcheva et al, 2021).
Comparison with inhalational anaesthetics
Even including disposable plastics and a reported 50% wastage rate, propofol is still considered to have the least overall impact on greenhouse gas emissions compared to volatile agents such as isoflurane and sevoflurane (Sherman et al, 2012). In addition, research by the NHS suggests that even when incorporating the electricity used to produce plastic syringes, propofol a much lower carbon footprint than inhalational anaesthetic gases by a large margin (Hu et al, 2021).
Education
Environmental education is essential in veterinary practices. It is suggested that a focus on interactions between the environment and human health, improving sustainability and addressing wider ethical and legal issues associated with sustainability for future populations would be beneficial in education (Jones and West, 2019). It is hoped that drug wastage can be reduced through education, feedback on current practice and random audits of staff knowledge regarding the correct disposal routes for waste propofol in practice (Mankes, 2012). A lot of interest has been shown in the topic of environmentalism and ways to reduce carbon footprint in veterinary practice. Equally, a greater understanding of pharmacokinetics may help to reduce the amount of propofol drawn up at the start of the case, thus preserving the unused propofol in the sterile vial to be used for future cases (Kaniyil et al, 2017).
Suggestions for propofol waste reduction
Suggestions for waste reduction in general include recycling, re-processing and donations (Koytcheva et al, 2021). While waste propofol cannot be reused for another patient because of the risk of cross contamination, in the author's experience left over syringes of propofol after the induction of anaesthesia have been used for euthanasia of other patients. Administering propofol administration before pentobarbital reduces muscle activity, thus giving the client a better perception of the event (Bullock et al, 2019).
One suggestion to reduce the financial burden was to display a price list to act as a visual reminder for staff when drawing up the drugs (Kaniyil et al, 2017). Likewise, financial incentives can be used to influence a positive environmental culture within the team (Koytcheva et al, 2021).
Companies should research product supply chains before purchasing items to make environmentally sound decisions. If suppliers are held accountable, they are more likely to provide sustainable products (Koytcheva et al, 2021).
Another suggestion to improve the environmental impact of veterinary anaesthesia was to switch off electronic equipment after use and use rechargeable batteries in equipment where possible (Jones and West, 2019).
Possible future innovations
In recent years the UK environmental agency permitted the recycling of contaminated medical PVC into tree ties, reducing the energy required for production by 85% (Jones and West, 2019). Bioplastics made from mushrooms or corn are being developed, but more research is required before these replacements become possible (Rasheed and Walraven, 2023). Neither idea is yet available to veterinary hospitals but could be indicative of a positive future for medical waste management.
Conclusions
Some amount of drug wastage is inevitable. The environmental risks posed by waste propofol are considered low; however, few data are available to quantify the volume of propofol entering our ecosystems and the effects that chronic exposure may pose (Allen et al, 2021).
Waste segregation is extremely important to help reduce both the environmental contamination and financial impact of waste disposal. It is reported that clinical waste disposal can be up to ten times more expensive than recycling systems. Likewise implementing the five R's of waste management (reducing, reusing, recycling, rethinking and researching) can lessen our impact on the planet. All staff working in practice should undergo appropriate waste disposal training.
Small changes by individuals can have a large impact on sustainability. However, it is important that any changes implemented in practice do not compromise the quality of patient care.
SUGGESTED FURTHER READING
- Jones RS, West E. Environmental sustainability in veterinary anaesthesia. Vet Anaesth Analg. 2019;46(4):409–420. https://doi.org/10.1016/j.vaa.2018.12.008
- Koytcheva MK, Sauerwein LK, Webb TL, Baumgarn SA, Skeels SA, Duncan CG. A systematic review of environmental sustainability in veterinary practice. Top Companion Anim Med. 2021;44:100550. https://doi.org/10.1016/j.tcam.2021.100550
KEY POINTS
- Waste in the operating room is an issue facing both human and animal anaesthetists.
- Incorrect disposal of drugs leads to environmental contamination. Propofol is highly mobile in soil, accumulates in fat and is toxic to aquatic life.
- When excess propofol is drawn up and subsequently wasted it is not just the end product that needs to be considered – the production of the raw ingredients also have a greater environmental impact.
- Waste of any form causes a financial burden on the hospital.