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Ecological Costs

Is propofol anaesthesia more environmentally friendly than inhalation? In this article, we look closely at why propofol is a better option.

Ecological Cost of TIVA

  • Production
    • Propofol constituents are sourced from multiple countries
    • Soy cultivation has been linked to deforestation
    • We should advocate for manufacturers to purchase sustainable sources of soy
  • Administration
    • No direct emission of GHG but carbon dioxide is produced as a result of the combustion of plastic consumables
    • Standard TIVA set-up totals ~ 270g of plastics which when combusted produces 1.4 Kg of carbon dioxide
      • 2 x 50ml Syringe
      • Extension tubing
      • 3-way taps
    • Energy required to run the infusion pumps
      • Energy sources of hospitals are variable and impact the lifecycle analysis
      • Renewable energy vs fossil fuels
  • Disposal
    • Large amounts of unused propofol are wasted ~ can be 30-50% so think carefully about how much you will need for each case
    • PBT index

Desflurane

  • Desflurane and Nitrous Oxide have the largest impact on the environment
  • Desflurane
    • The twenty-year global-warming potential, GWP (20), for desflurane is 3714, meaning that one tonne of desflurane emitted is equivalent to 3714 tonnes of carbon dioxide in the atmosphere, much higher than sevoflurane or isoflurane. It also has the highest radiated efficiency (heat-trapping effect).
    • Electricity is required to keep the vaporiser at 39 degrees celsius to allow desflurane to become volatile
    • MAC % is very high. On a per-MAC-hour basis, the total life cycle GHG impact of desflurane is more than 20 times higher than Isoflurane and Sevoflurane
    • Low metabolism
  • Desflurane should be restricted to cases where they may decrease morbidity and mortality
  • Desflurane has already been removed from the back bar of the anaesthetic machine in some hospitals i.e. not an option

Nitrous Oxide

  • Nitrous Oxide has the largest carbon footprint of the anaesthetic gases
    • Longest atmospheric lifetime
    • It was 80% of the total UK National Health Service anaesthetic gas footprint in 2019/2020
  • The Nitrous Oxide Project: aims to reduce anaesthetic nitrous oxide emissions
    • Minimising system waste
      • Wastage from piped manifold systems is a far more significant problem than that of clinical use
    • Educating and promoting ecologically friendly (“green”) practice
    • Nitrous oxide catalytic cracking technologies

Mitigation Strategies

  • Aggregation of marginal gains: small improvements every day, everywhere and anywhere, have a compound effect
  • Reduction in fresh flow gas rates to lower the consumption of volatile agents when inhalational agents are used to maintain anaesthesia
    • This will increase the use of CO2 absorbers
  • Increase in fresh flow gas rates to lower the consumption of CO2 absorbers. Use TIVA to maintain anaesthesia when possible
    • Flows of around 3 L/minute using soda lime, can reduce both the economic and environmental burden
    • The environmental benefit is more pronounced if a high proportion of the country’s electrical use is renewable
  • End-tidal control
    • Monitors and automatically adjusts the levels of anaesthetic concentration in a closed-circuit system across a specified flow range of 0.5–10 litres per minute.
  • Deltasorb is a device that uses a sieve-like filtering matrix to adsorb inhalational anaesthetic gases. The canisters are returned to the vendor where the captured anaesthetics are extracted, liquefied, and processed into medical-grade anaesthetics
  • Promotion of TIVA and regional anaesthesia as primary techniques

Reduce, Reuse, Recycle

  • Promotion of sustainable practices can help negate the negative environmental effects of anaesthesia
  • Reduce
    • Propofol waste can be reduced 10 fold by using only 20ml ampoules (Mankes 2012)
    • Prescribing oral paracetamol preoperatively greatly decreases associated emissions (Myo 2021)
      • 1 g oral paracetamol generates just 1/68th of the emissions of intravenous paracetamol in glass bottles
      • 1 g oral paracetamol generates 1/45th of the emissions compared with plastic bottles
  • Reuse
    • Life cycle assessment to model the environmental and financial costs of different scenarios of replacing reusable anaesthetic equipment with single-use variants (Mc Gain 2017)
      • Outcomes were dependent on the power mix source of the country
        • Australia increase 9%
        • UK decrease 84%
        • US decrease 48%
      • The source of hospital electricity significantly alters the relative environmental effects of reusable items
  • Recycle
    • Up to 25% of operating theatre waste is generated by anaesthetists
      • 40-60% is recyclable
    • Plastic and glass represents a large proportion of recyclable waste
    • Waste segregation for disposal is highly user-dependent
    • The Association for Perioperative Practice in the UK has a series of guidelines for theatre waste management
    • One-third of clinical waste is inappropriately assigned
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Introduction to Using Total Intravenous Anaesthesia (TIVA)

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