Gases anestésicos: impacto ambiental y alternativas
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Anaesthetic gases: environmental impact and alternatives
Melissa Bosenberg
South Afr J Anaesth Analg 2011;17(5):345-348
Abstract
Little consideration has been given to the environmental impact of gaseous anaesthetic use. All currently used volatile anaesthetics are halogenated and chemically similar to chlorofluorocarbons (CFCs), giving them the potential to impact the environment negatively via both ozone depletion and global warming. Overall contribution to climate change is dependent on both these environmental effects, as well as the quantities released into the atmosphere. This review of the current data provides an insight into the overall ecotoxicity of volatile agents and gives alternatives which may be employed to limit environmental load. Results from the studies reveal that global warming potential and ozone depletion potential are significant for all volatiles, especially when combined with nitrous oxide use. However, because atmospheric levels are estimated to be small when compared to gaseous emissions from industrial and agricultural sources, the actual percentage contribution to climate change is small. Despite these findings, the cumulative effects of small contributors to climate change should not be underestimated, especially with increasing numbers of future anaesthetics and a decreasing CFC load. The carbon footprint of an individual anaesthetist is significantly increased by the daily use of volatile anaesthetic agents and recognised alternatives may be utilised to minimise this.
http://www.sajaa.co.za/index.php/sajaa/article/view/844/995
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| Potencial de calentamiento global de los anestésicos inhalados: aplicación para el uso clínico |
Global warming potential of inhaled anesthetics: application to clinical use.
Ryan SM, Nielsen CJ.
Department of Anesthesia and Perioperative Care, University of California, San Francisco, San Francisco, California 94143, USA.ryans@anesthesia.ucsf.edu
Anesth Analg. 2010 Jul;111(1):92-8. Epub 2010 Jun 2.
Abstract
BACKGROUND: Inhaled anesthetics are recognized greenhouse gases. Calculating their relative impact during common clinical usage will allow comparison to each other and to carbon dioxide emissions in general. METHODS: We determined infrared absorption cross-sections for sevoflurane and isoflurane. Twenty-year global warming potential (GWP(20)) values for desflurane, sevoflurane, and isoflurane were then calculated using the present and previously published infrared results, and best estimate atmospheric lifetimes were determined. The total quantity of each anesthetic used in 1 minimal alveolar concentration (MAC)-hour was then multiplied by the calculated GWP(20) for that anesthetic, and expressed as "carbon dioxide equivalent" (CDE(20)) in grams. Common fresh gas flows and carrier gases, both air/oxygen and nitrous oxide (N2O)/oxygen, were considered in the calculations to allow these examples to represent common clinical use of inhaled anesthetics. RESULTS: GWP(20) values for the inhaled anesthetics were: sevoflurane 349, isoflurane 1401, and desflurane 3714. CDE(20) values for 1 MAC-hour at 2 L fresh gas flow were: sevoflurane 6980 g, isoflurane 15,551 g, and desflurane 187,186 g. Comparison among these anesthetics produced a ratio of sevoflurane 1, isoflurane 2.2, and desflurane 26.8. When 60% N2O/40% oxygen replaced air/oxygen as a carrier gas combination, and inhaled anesthetic delivery was adjusted to deliver 1 MAC-hour of anesthetic, sevoflurane CDE(20) values were 5.9 times higher with N2O than when carried with air/O2, isoflurane values were 2.9 times higher, and desflurane values were 0.4 times lower. On a 100-year time horizon with 60% N2O, the sevoflurane CDE(100) values were 19 times higher than when carried in air/O2, isoflurane values were 9 times higher, and desflurane values were equal with and without N2O. CONCLUSIONS: Under comparable and common clinical conditions, desflurane has a greater potential impact on global warming than either isoflurane or sevoflurane. N2O alone produces a sizable greenhouse gas contribution relative to sevoflurane or isoflurane. Additionally, 60% N2O combined with potent inhaled anesthetics to deliver 1 MAC of anesthetic substantially increases the environmental impact of sevoflurane and isoflurane, and decreases that of desflurane. N2O is destructive to the ozone layer as well as possessing GWP; it continues to have impact over a longer timeframe, and may not be an environmentally sound tradeoff for desflurane. From our calculations, avoiding N2O and unnecessarily high fresh gas flow rates can reduce the environmental impact of inhaled anesthetics
http://www.anesthesia-analgesia.org/content/111/1/92.full.pdf+html
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