Low-flow anesthesia

1. Anesth Analg. 2021 Oct 1;133(4):826-835. doi: 10.1213/ANE.0000000000005504.

Environmental and Occupational Considerations of Anesthesia: A Narrative Review and Update.

Varughese S(1), Ahmed R.

With an estimated worldwide volume of 266 million surgeries in 2015, the call for general inhalation anesthesia is considerable. However, widely used volatile anesthetics such as N2O and the highly fluorinated gases sevoflurane, desflurane, and isoflurane are greenhouse gases, ozone-depleting agents, or both. Because these agents undergo minimal metabolism in the body during clinical use and are primarily (≥95%) eliminated unchanged via exhalation, waste anesthetic gases (WAGs) in operating rooms and postanesthesia care units can pose a challenge for overall elimination and occupational exposure. The chemical properties and global warming impacts of these gases vary, with atmospheric lifetimes of 1-5 years for sevoflurane, 3-6 years for isoflurane, 9-21 years for desflurane, and 114 years for N2O. Additionally, the use of N2O as a carrier gas for the inhalation anesthetics and as a supplement to intravenous (IV) anesthetics further contributes to these impacts. At the same time, unscavenged WAGs can result in chronic occupational exposure of health care workers to potential associated adverse health effects. Few adverse effects associated with WAGs have been documented, however, when workplace exposure limits are implemented. Specific measures that can help reduce occupational exposure and the environmental impact of inhaled anesthetics include efficient ventilation and scavenging systems, regular monitoring of airborne concentrations of waste gases to remain below recommended limits, ensuring that anesthesia equipment is well maintained, avoiding desflurane and N2O if possible, and minimizing fresh gas flow rates (eg, use of low-flow anesthesia). One alternative to volatile anesthetics may be total intravenous anesthesia (TIVA). While TIVA is not associated with the risks of occupational exposure or atmospheric pollution that are inherent to volatile anesthetic gases, clinical considerations should be weighed in the choice of agent. Appropriate procedures for the disposal of IV anesthetics must be followed to minimize any potential for negative environmental effects. Overall, although their contributions are relatively low compared with those of other human-produced substances, inhaled anesthetics are intrinsically potent greenhouse gases and pose a risk to operating-room personnel if not properly managed and scavenged. Factors to reduce waste and minimize the future impact of these substances should be considered.

DOI: 10.1213/ANE.0000000000005504 PMCID: PMC8415729 PMID: 33857027 [Indexed for MEDLINE]

2. AANA J. 2022 Aug;90(4):253-262.

Reducing the Carbon Footprint of Anesthesia: Low-Flow Anesthesia and Other Techniques.

McGowan LS(1), Macksey LF(2).

According to a joint statement by the US National Academy of Sciences and the UK Royal Society, it is now more certain than ever that human activity is a leading cause of rapid, accelerated climate change. Our volatile anesthetics have up to 2,000 times more greenhouse gas contributing potential than the same amount of carbon dioxide, yet no emission regulations have been imposed. The carbon footprint of volatile agents exists in all anesthesia practices, indirectly affecting all humans. It manifests daily in the clinical practice of over 30,000 certified registered nurse anesthetists in the United States, as their anesthetic choices directly impact the environment. However, education about anesthetic choice and its impact has been overlooked, making many anesthesia providers unaware of meaningful ways to reduce ecological and economic costs. Decreasing the use of volatile agents by low-flow techniques and the use of a total intravenous anesthetic could dramatically reduce carbon footprint produced by anesthesia. The authors review other advantages of limiting or avoiding volatile agents beyond green anesthesia such as decreased costs, reduced postoperative nausea and vomiting, and lowering the risk of malignant hyperthermia.

PMID: 35943750 [Indexed for MEDLINE]

3. AANA J. 2021 Feb;89(1):27-33.

Evidence-Based Project: Cost Savings and Reduction in Environmental Release With Low-Flow Anesthesia.

Edmonds A(1), Stambaugh H(2), Pettey S(3), Daratha KB(4).

Volatile anesthetic agents act as greenhouse gases. Low-flow anesthesia techniques (≤1 L/min) are associated with lower costs. Decreasing volatile anesthetic delivery provides safe and effective strategies for anesthesia providers to decrease costs and reduce environmental pollution. This evidence-based project aimed to estimate cost savings and reduction in the environmental release of anesthetic gases, under simulated lower fresh gas flow (FGF) practices. For each surgical case, the exhaled anesthetic gas percent and FGF data were used to calculate the volume of fluid volatile anesthetic. The fluid volatile anesthetic for each case was then estimated using simulated FGFs. Changes in volatile agent cost and environmental release of anesthetic gases were predicted. Sevoflurane was the most commonly used volatile agent. The mean FGF for cases using sevoflurane was 2.5 L/min. The simulated FGF of 1 L/min FGF across all agents predicted a 48% ($50,892) reduction in costs of volatile anesthetics and a 42% (33 metric tons of carbon dioxide equivalent) decrease in carbon emissions. Simulated low-flow anesthesia demonstrated cost savings and environmental conservation. Project findings align with current literature showing that lowering FGFs represents an area of cost containment and an opportunity to lessen the environmental impact of anesthesia.

PMID: 33501906 [Indexed for MEDLINE]

4. Pediatr Qual Saf. 2023 Dec 12;8(6):e708. doi: 10.1097/pq9.0000000000000708. eCollection 2023 Nov-Dec.

Sustainability Standards in Pediatric Anesthesia: Quality Initiative to Reduce Costly Environmentally Harmful Volatile Anesthetics.

Waberski AT(1), Pestieau SR(1), Vazquez-Colon C(1), Cronin J(1), Braffett BH(2).

BACKGROUND: The emission and entrapment of greenhouse gases (GHG) inside the atmosphere is one of the leading causes of global warming. Commonly administered anesthetics have global warming potential up to 2,000 times greater than carbon dioxide. This Quality Improvement (QI) initiative aimed to develop a set of sustainability standards to reduce volatile anesthetic GHG emissions and costs at a children's hospital. METHODS: In January 2020, the QI project team implemented education sessions for clinical staff on the environmental impact of volatile anesthetics, bedside clinical reminders, resource guides on sustainable anesthesia practices, preset low-flow gas levels on anesthesia machines, relocated and reduced the number of available vaporizers, and implemented policies to standardize clinical practice. Using hospital pharmacy purchase order data between 2018 and 2022, GHG emissions and costs from three commonly used volatile anesthetics (Isoflurane, Sevoflurane, and Desflurane) were compared using metric ton carbon dioxide equivalents. RESULTS: During 3 years, GHG emissions from volatile anesthetics were significantly reduced by 77%, with most of the reduction attributed to the reduced use and eventual elimination of Desflurane. Purchase costs were also significantly reduced during this period by 41%. CONCLUSIONS: This QI project successfully decreased GHG emissions over 3 years by simultaneously reducing the use of costly and environmentally harmful volatile anesthetic, Desflurane, and increasing the use of low-flow anesthesia. This study addresses our anesthesia practices and healthcare system's impact on the pediatric population and proposes simple interventions to mitigate the negative consequences of current practices.

DOI: 10.1097/pq9.0000000000000708 PMCID: PMC10715793 PMID: 38089832

5. Can J Anaesth. 2023 Mar;70(3):301-312. doi: 10.1007/s12630-022-02393-z. Epub 2023 Feb 22.

A call for immediate climate action in anesthesiology: routine use of minimal or metabolic fresh gas flow reduces our ecological footprint.

Rübsam ML(1), Kruse P(2), Dietzler Y(3), Kropf M(4), Bette B(2), Zarbock A(5), Kim SC(2), Hönemann C(6)(7).

PURPOSE: Climate change is a global threat, and inhalational anesthetics contribute to global warming by altering the photophysical properties of the atmosphere. On a global perspective, there is a fundamental need to reduce perioperative morbidity and mortality and to provide safe anesthesia. Thus, inhalational anesthetics will remain a significant source of emissions in the foreseeable future. It is, therefore, necessary to develop and implement strategies to minimize the consumption of inhalational anesthetics to reduce the ecological footprint of inhalational anesthesia. SOURCE: We have integrated recent findings concerning climate change, characteristics of established inhalational anesthetics, complex simulative calculations, and clinical expertise to propose a practical and safe strategy to practice ecologically responsible anesthesia using inhalational anesthetics. PRINCIPAL FINDINGS: Comparing the global warming potential of inhalational anesthetics, desflurane is about 20 times more potent than sevoflurane and five times more potent than isoflurane. Balanced anesthesia using low or minimal fresh gas flow (≤ 1 L·min-1) during the wash-in period and metabolic fresh gas flow (0.35 L·min-1) during steady-state maintenance reduces CO2 emissions and costs by approximately 50%. Total intravenous anesthesia and locoregional anesthesia represent further options for lowering greenhouse gas emissions. CONCLUSION: Responsible anesthetic management choices should prioritize patient safety and consider all available options. If inhalational anesthesia is chosen, the use of minimal or metabolic fresh gas flow reduces the consumption of inhalational anesthetics significantly. Nitrous oxide should be avoided entirely as it contributes to depletion of the ozone layer, and desflurane should only be used in justified exceptional cases.

DOI: 10.1007/s12630-022-02393-z PMCID: PMC10066075 PMID: 36814057 [Indexed for MEDLINE]

6. Paediatr Anaesth. 2020 Oct;30(10):1139-1145. doi: 10.1111/pan.13994. Epub 2020 Aug 29.

The implementation of low-flow anesthesia at a tertiary pediatric center: A quality improvement initiative.

Glenski TA(1), Levine L(1).

INTRODUCTION: Anesthesia machines have evolved over the years to excel in delivering low-flow anesthesia (<1 L fresh gas flow) in a closed-circuit system, with the obvious benefits being decreased costs and reduced emissions of greenhouse gases. At a pediatric hospital that provides over 25 000 anesthetics a year, a quality improvement project was initiated with the aim of decreasing the amount of sevoflurane used per anesthetic by 20% over the course of a year. METHODS: Three Plan-Do-Study-Act cycles involving gathering comparative data, departmental education, improvement updates on our huddle board, and intraoperative confirmation rounds were completed. The bottles of sevoflurane used and the total number of anesthetics performed were collected each month. To account for the fluctuation of anesthetic cases per month, a metric of "Anesthetics Performed per Bottle of Sevoflurane Used" was created. RESULTS: Compared to a prior twelve-month period, the Anesthetics Performed per Bottle of Sevoflurane Used were higher with a mean increase of 25%. The bottles of sevoflurane used per month was lower with a mean decrease of 20%. The carbon footprint of our sevoflurane use was also decreased and extrapolated over a year, and the decrease was equivalent to 70 000 miles driven, over 3,200 gallons of gasoline consumed, or over 31000 pounds of coal burned. CONCLUSION: A QI initiative aimed at changing the practice of delivering at least 2L fresh gas flow to delivering a low-flow anesthetic has been a successful value-added enhancement to our pediatric anesthesia practice.

DOI: 10.1111/pan.13994 PMID: 32786105 [Indexed for MEDLINE]

7. J Grad Med Educ. 2024 Apr;16(2):175-181. doi: 10.4300/JGME-D-23-00402.1. Epub 2024 Apr 15.

How an Audit-and-Feedback-Based Educational Program Contributed to a Reduction in Environmentally Harmful Waste Anesthetic Gases Among Anesthesiology Residents.

Nordin EJ(1), Dugan SM(2), Kusters AC(3), Schimek CA(4), Sherman KA(5), Ebert TJ(6).

Background Waste anesthetic gases (WAGs) contribute to greenhouse gas emissions. US anesthesiology resident education on how to reduce WAG-associated emissions is lacking, so we developed an electronic audit-and-feedback-based program to teach residents to reduce fresh gas flow (FGF) and WAG-associated emissions. Objective To assess the program's effectiveness, we measured individual and combined mean FGF of residents during their first, second, and last weeks of the 4-week rotation; then, we calculated the extrapolated annual emissions based on the combined resident mean FGFs. Resident attitudes toward the program were surveyed. Methods During 4-week rotations at a teaching hospital, anesthesia records were scanned to extract resident-assigned cases, FGF, and volatile anesthetic choice during the 2020-2021 academic year. Forty residents across 3 training years received weekly FGF data and extrapolated WAG-associated emissions data via email. Their own FGF data was compared to the low-flow standard FGF of ≤1 liter per minute (LPM) and to the FGF data of their peer residents on rotation with them. An online survey was sent to residents at the end of the project period. Results Between their first and last weeks on rotation, residents decreased their mean FGF by 22% (1.83 vs 1.42 LPM; STD 0.58 vs 0.44; 95% CI 1.67-2.02 vs 1.29-1.56; P<.0001). Ten of 18 (56%) residents who responded to the survey reported their individual case-based results were most motivating toward practice change. Conclusions An audit-and-feedback-based model for anesthesiology resident education, designed to promote climate-conscious practices with administration of volatile anesthetics, was effective.

DOI: 10.4300/JGME-D-23-00402.1 PMCID: PMC11234298 PMID: 38993317 [Indexed for MEDLINE]

8. Br J Anaesth. 2024 Jul 22:S0007-0912(24)00389-1. doi: 10.1016/j.bja.2024.06.024. Online ahead of print.

Efficient inhaled anaesthetic delivery requires managing fresh gas flow from induction through emergence.

Feldman JM(1), Sherman JD(2).

DOI: 10.1016/j.bja.2024.06.024 PMID: 39043522