Environmental Sustainability: Opportunity or Cost for Anaesthesia?

Environmental Sustainability: Opportunity or Cost for Anaesthesia?

Background

Environmental sustainability in healthcare is rather dry (as its direct clinical implications are only modest), but very important topic in the 21^st century as the threat of global warming and climate change is getting more ferocious, which is most likely to be the result of human activity since the mid-20^th century.¹

To tackle global warming, the parliament of UK established the Climate Change Act 2008, aiming to reduce the UK’s greenhouse gas emission by at least 80% by 2050.² In the same year, the World Health Organisation also identified five recommendations for the global research community to protect health from climate change, which translated by the Association of Anaesthetists into six themes.³ 

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So, why is anaesthesia as a specialty playing such a significant role in addressing climate change? It is because we almost forget that pretty much all the inhalational anaesthetic agents are greenhouse gases that make the earth warmer by trapping energy inside the atmosphere as well as destructing the ozone layer.^4,5 However, the contributions of them have been graciously excused under the guise of medical necessity. Corresponding to other industries, two important factors, i.e. cost and carbon footprint will always be associated in every stage from manufacturing, operating to waste disposal. The econometric general equilibrium assessment is the area that we concern. 

Overall, the NHS in England has an annual carbon footprint of 22.8 million tonnes of carbon dioxide, which consists of procurement (40%), energy (23%), travel (24%) and commissioned outside NHS (14%). Focusing on anaesthesia alone, it came to light that anaesthetic gases already constitute 5% of the carbon footprint for the hospital, which is considerable.⁶ Therefore, to achieve green anaesthesia, the application of ‘5R’ approach (reduce, reuse, recycle, rethink, research) can be implemented to evaluate its feasibility.

Reduce

The most effective way to achieve ‘green’ is fairly straightforward that is cutting down the resource used in the first instance, or at least swap to a more environmentally one.

The impact of greenhouse gases is measured as global warming potential (GWP) over the 100-year horizon (GWP₁₀₀). All the gases are calibrated with the well-known greenhouse gases CO₂ (GWP₁₀₀=1). The GWP₁₀₀ of nitrous oxide is 298, sevoflurane 130, isoflurane 510 and desflurane 2540.⁷ Sherman et al.⁸ used modelling techniques to calculate to CO_2e to provide one MAC hour of anaesthesia from manufacturing, transport to disposal. It turns out that nitrous oxide and desflurane cause the most warming despite nitrous oxide itself has the least GWP₁₀₀ among them all. Hence, a suggestion has been made to avoid the use of nitrous oxide and desflurane as the inhalational anaesthetic. Sevoflurane, as a result, has gained popularity due to its rapid onset and recovery similar to desflurane, but has lower GWP, non-pungent smell and is cheaper to administer at lowest allowable flow rates for cases less than 2 MAC hours using Dion’s formula in multiple pieces of literature.^9,10

Besides, the idea of low-flow inhalational anaesthesia has been widely recognised as having less environmental impact and less expensive than high-flow anaesthesia on top of other benefits such as maintaining heat and humidity in the breathing circuits without compromising clinical outcome.^11,12 Low-flow fresh gas flow rates are ideally be used in maintenance anaesthesia.

In the past, used gases that are exhaled unchanged will escape or actively ventilate to the outside atmosphere to minimise pollution within the theatre environment for health and safety reason.¹³ The implementation of the scavenging system allows for the collection, capture and disposal of gases to avoid the anaesthetic gases being released to the atmosphere. Berry et al.¹⁴ reported the waste anaesthetic gas scavenging system has 99% efficiency in elimination, while a clinical trial performed by Jänchen et al.¹⁵ has shown that Zeolite can collect 62-86% used desflurane. The scavenging system has greatly reduced the release of anaesthetic gas to the atmosphere that minimising its environmental damages.

Reuse / Recycle

The modern scavenging technologies such as Dynamic Gas Scavenging System and Deltasorb canister by Blue Zone Technologies can even purify and self-sterilising 99% of the escaped anaesthetic gas to be reused.¹⁶

Furthermore, a recent study with six operating rooms in an Australia hospital has demonstrated that it is practically cost-saving (£18,000 per annum) by converting from single-use to reusable anaesthetic equipment, though at the expense of additional 10% CO₂ emissions.¹⁷ Nevertheless, Rowley and Dingwall¹⁸ argued that the reasoning of supporting single-use devices in anaesthesia are down to the risk of cross-infection of prion from imperfect sterilisation and decontamination processes. They further explained that the cost of manufacturing and the quality of single-use equipment justified its purpose as a one-time use only device, as re-using it may reduce its efficacy and cause iatrogenic harm to the patient.

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It remains unclear whether the risk of cross-infection is real or perceived. There has been no any reported case in the last 40 years of anaesthetic airway use as expression of prion in lymphoid tissues such as tonsil is thought to be highly infectious theoretically, even though the enforcement of disposable anaesthetic equipment only began in 2001.¹⁹ In addition, several novel methods for disinfection has proven to be effective in prion inactivation, if any.^20,21 A new blood test described by Concha-Marambio et al.²² for prion has 100% sensitivity, and specificity could potentially be added as a pre-op assessment to screen for carrier. After all, the inertia of remain using disposable anaesthetic equipment is likely for patient reassurance and avoiding the administrative ramifications that could entail for the reusable equipment to be tracked shall any adverse event happen by recording the serial number of individual anaesthetic equipment as per surgical equipment.²³    

Rethink

Another proposal is to substitute inhalational anaesthesia to total intravenous anaesthesia (TIVA) and regional anaesthesia. Although there has been a continuing debate whether TIVA or inhalational anaesthetics are best for day case with both methods have their pros and cons, ultimately the choice is often down to anaesthetists’ personal preference and experiences.²⁴ While having consider about environmental sustainability, propofol used in TIVA has minimal GWP and cost less for longer procedures (three hours) compared to sevoflurane gas anaesthesia, which may tilt the balance slightly in favour of its use. If the procedure is shorter (<1hr), sevoflurane is marginal cheaper.^{10, 25}

Another cost-saving step is to re-emphasise and redesign the layout of the anaesthetic room to encourage proper waste segregation. 40% of anaesthetic waste was, in fact, domestic waste, which can be incinerated at a cheaper cost, saving ≈ £620 per operating theatre per year. Each operating theatre also produced 230kg of sharps a year, and 40% of them were inappropriately disposed of packaging, metals, plastic etc. that could potentially be recycled.²⁶

Research

As part of human nature to continually search for a better alternative, Xenon has renewed the attention as the next novel anaesthetic gas.²⁷ It is an inert gas that naturally found in the ozone layer and does not trap heat. It works by selectively blocking the NMDA receptor and was first used in anaesthesia in 1946.²⁸ Its chemically inert properties have demonstrated some neuroprotective effects and haemodynamic stability. With acquisition price at £7 per litre, the financial disadvantage is the barrier to its routine clinical use. Nonetheless, Zornow and Neice²⁹ are sceptical that should Xenon become widely used, it might encounter unexpected shortages or further price spikes due to its rarity and the additional investment required to add Xenon purification ability to current air separation unit that provides liquid oxygen and nitrogen. The cardiovascular stability of Xenon can also be achieved by administration of vasopressor or carefully dosing of inhalation agents. Researchers still believe Xenon holds remarkable promise for green anaesthesia if able to develop better closed-system anaesthesia and scavenging capability to minimise its operational cost.     

Conclusion

Healthcare is more than just medicine. As with other industries, we play a vital role in environmental sustainability. Many ideas discussed above suggesting green anaesthesia is, in fact, feasible and can be significantly cost-saving, yet more research needs to be done to assess their patient safety as it must remain the priority. 
 

References

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