Percentage of cases where carbon dioxide equivalents (CO₂ eq) normalized by hour for cases receiving halogenated agents and/or nitrous oxide is less than CO₂ eq of 2% sevoflurane at 2L FGF = 2.83 kg CO₂/hr during the maintenance period of anesthesia OR the Total CO2e is less than 2.83 kg CO2.

Reducing emissions can decrease public health harm and cost of anesthesia without compromising patient care. ^1–13

“Global Warming Potential (GWP) is a measure of how much a given mass of greenhouse gas contributes to global warming over a specified period of time. The Intergovernmental Panel on Climate Change uses 100 years; however, 20, 50, 500 years are common as well, depending on the gas in question. GWP is a relative scale that compares the contribution of the gas in question to that of the same mass of carbon dioxide. The GWP of carbon dioxide, by definition, is one.”⁸  

Intubation to Extubation time

• Cases with an ETT or LMA as determined by MPOG phenotype Anesthesia Technique: General (value codes 1,2,3,6)
• Cases where halogenated hydrocarbons and/or nitrous oxide were administered during the maintenance phase of anesthesia

• Cases without an ETT or LMA placed (determined by MPOG phenotype Anesthesia Technique: General (value codes 0,4,5)
• Cases with documentation of Nitric Oxide use
• Cases in which halogenated hydrocarbons or nitrous oxide are NOT used during the maintenance phase of anesthesia
• Cases without automated FGF data (ie those that are manually entered)

Mean efficiency less than or equal to carbon dioxide equivalents of 2% sevoflurane at 2L FGF = 2.83 kg CO₂/hr 

OR

Total CO2eq for the case is less than or equal to 2.83 kg CO2

Measure Start 

• Intubation. If not available, then
• Induction End

Measure End 

• Extubation Time. If not available, then 
• LMA Removal Time. If not available, then
• Surgery End. If not available, then
• Patient Out of Room. If not available, then
• Anesthesia End.

Artifact Values for flows and inhalational agents will be assessed and considered as artifact if inside the following ranges:

• Nitrous Oxide Flows: <0.2 L/min
• Isoflurane Insp %: <0.3%
• Sevoflurane Insp %: <0.4%
• Desflurane Insp %: <1.2%
• Nitrous Oxide Insp % <20%

CO₂ equivalents determined by calculating the pollutant total for the time period and dividing by the total number of minutes during the maintenance period.

Pollutant total: [Inspired agent concentration (%) * fresh gas flow (l/min)]  * GWP₁₀₀ ]

1. Calculate CO₂ eq for each minute of Sevoflurane %, Isoflurane and Desflurane %  *
2. Calculate CO₂ eq for each minute of Nitrous Oxide % or Nitrous Oxide flows **
3. Sum CO₂ equivalents 
4. Divide by total count of included minutes: Total CO₂ eq/Total # of minutes
   • Included Minute = minute within measure bounds, with both halogenated agent and flows present
5. Multiply Total CO₂ eq/min * 60 = Mean CO₂ eq per hour

* CO₂ eq for Sevoflurane, Isoflurane or Desflurane (%):

1. Convert agent % → mLs of agent/min: (FGF (l/min) x 1,000 x agent %) / 100 
2. Convert mls/min → moles:  agent mL / 24,400
   • The Editors of Encyclopedia Britannic
3. Convert moles → mass: (agent moles x MW of agent) / 1,000
4. Convert mass → CO₂ equivalents: agent mass x GWP of agent 

** CO₂ eq For Nitrous Oxide:

For cases with documented Nitrous Oxide % but Nitrous Oxide flow is not reported, then use Nitrous Oxide % and FGF:

• Divide Nitrous Oxide % / 100 = N
• Convert N → mLs/min: (FGF (l/min) x 1,000 x N) 
• Convert mls/min → moles:  N mL / 24,400
• Convert moles → mass: (N moles x MW of agent) / 1,000
• Convert mass → CO₂ equivalents: N mass x GWP of agent

For cases with both valid Nitrous Oxide % and Nitrous Oxide flows reported, only Nitrous Oxide flow values will be considered (N2O values reported as % will be ignored):

1. Convert Nitrous Oxide (l/min) → mols/min: Nitrous Oxide  / 24.4 = Nmol
2. Convert Nmol → N20 mass (kg/min): (Nmol *44) / 1,000 
3. Convert Nmass → CO₂ equivalents: Nmass * GWP 

From Greening the Operating Room and Perioperative Arena: Environmental Sustainability for Anesthesia Practice:

“Global Warming Potential (GWP) is a measure of how much a given mass of greenhouse gas contributes to global warming over a specified period of time. The Intergovernmental Panel on Climate Change uses 100 years; however, 20, 50, 500 years are common as well, depending on the gas in question. GWP is a relative scale that compares the contribution of the gas in question to that of the same mass of carbon dioxide. The GWP of carbon dioxide, by definition, is one.”(Greening the Operating Room )

Table adapted from American Society of Anesthesiologists’ Task Force on Environmental Sustainability Committee on Equipment and Facilities: Greening the Operating Room and Perioperative Arena: Environmental Sustainability for Anesthesia Practice^{(?Greening the Operating Room )}

*Nitrous oxide value is derived as an average of the range provided on the EPA website: 265-298.

Coming Soon! Carbon dioxide equivalents will be converted to miles driven equivalents based on EPA data found here: https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator

Not applicable

All providers signed in for at least 30 minutes during the time when halogenated agent or nitrous oxide are documented.

1. Epa US, OAR: Understanding global warming potentials 2016 at <https://www.epa.gov/ghgemissions/understanding-global-warming-potentials>
2. Hodnebrog Ø, Aamaas B, Fuglestvedt JS, Marston G, Myhre G, Nielsen CJ, Sandstad M, Shine KP, Wallington TJ: Updated Global Warming Potentials and Radiative Efficiencies of Halocarbons and Other Weak Atmospheric Absorbers. Rev Geophys 2020; 58:e2019RG000691
3. Andersen MPS, Nielsen OJ, Wallington TJ, Karpichev B, Sander SP: Assessing the Impact on Global Climate from General Anesthetic Gases. Anesthesia & Analgesia 2012; 114:1081
4. The Editors of Encyclopedia Britannica: mole 2020 at <https://www.britannica.com/science/mole-chemistry>
5. Biro P: Calculation of volatile anaesthetics consumption from agent concentration and fresh gas flow. Acta Anaesthesiol Scand 2014; 58:968–72
6. Hendrickx JF: The pharmacokinetics of inhaled anesthetics and carrier gases. Belgium: Ghent University 2004
7. Lowe HJ, Ernst EA: The Quantitative Practice of Anesthesia: Use of Closed Circuit. Williams & Wilkins, 1981 at <https://play.google.com/store/books/details?id=W2hsAAAAMAAJ>
8. Greening the Operating Room at <https://www.asahq.org/about-asa/governance-and-committees/asa-committees/environmental-sustainability/greening-the-operating-room>
9. Barwise JA, Lancaster LJ, Michaels D, Pope JE, Berry JM: An Initial Evaluation of a Novel Anesthetic Scavenging Interface. Anesthesia & Analgesia 2011; 113:1064
10. Tjus MEA: Destruction of Medical N2O in Sweden doi:10.5772/32169
11. Eisenkraft JB, McGregor DG: Waste Anesthetic Gases and Scavenging Systems 2013:pp 125–47 doi:10.1016/b978-0-323-11237-6.00005-4
12. Feldman JM: Managing fresh gas flow to reduce environmental contamination. Anesth Analg 2012; 114:1093–101
13. McGain F, Muret J, Lawson C, Sherman JD: Environmental sustainability in anaesthesia and critical care. Br J Anaesth 2020; 125:680–92