This measure seeks to increase efficient (based on global warming potential) use of inhalational anesthetic agents.  2.83 kg CO₂ equiavlents per hour is considered efficient use, and is equivalent to 2 l/min of 2% sevoflurane.  This measure analyzes the percentage of cases where carbon dioxide equivalents (CO₂ eq) normalized by hour for cases receiving inhalational anesthetic agents (desflurane, isoflurane, sevoflurane, or nitrous oxide) is less than CO₂ eq of 2% sevoflurane at 2L FGF = 2.83 kg CO₂/hr or the Total CO₂ eq is less than 2.83 kg CO₂ for the maintenance period of anesthesia.

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

Patients with an ETT or LMA (determined by Anesthesia Technique: General value codes: 1,2,3) (value code 6 might be excluded)

• Cases without an ETT or LMA placed (determined by Anesthesia Technique: General value codes: 0,4,5,6)
• Cases without an inhalational agent (desflurane, sevoflurane, isoflurane, or nitrous oxide) administration
• Cases with documentation of Nitric Oxide use
• Cases with only manually entered fresh gas flow values (fresh gas flow values must be automated to be considered for this measure).

For the maintenance phase of anesthesia:

• Mean CO₂ equivalents for a case is ≤ 2.83 kg CO₂/hr.  This is equivalent to administering 2% sevoflurane at 2 l/min FGF,
• Total CO₂ equivalents are less than or equal to 2.83 kg CO_{2 .}

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.

• If Fresh Gas Flow Total (MPOG Concept ID: 3214) is documented for the case, this concept will be used to determine success in the setting of inhaled anesthetic agents or nitrous oxide use.
• If Fresh Gas Flow Total (MPOG Concept ID: 3214) is not documented for the case, MPOG will calculate Fresh Gas Flow: Flows Oxygen (ID: 3215) + Flows Air (ID: 3220) + Flows Nitrous Oxide (ID: 3225)

Only inspired agents are considered for this calculation. SItes must ensure the inspired agent concentration are integrated with the electronic health record to participate in this measure. Maintenance period is defined as measure start to measure end. See Appendix for how minutes are included before calculating kg CO₂ equivalents.

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 inhaled anesthetic 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 

** Calculating CO₂ eq For Nitrous Oxide:

For cases with only Nitrous Oxide reported as inspired (%), convert Nitrous Oxide (N₂O) reported as inspired (%) to L/min: (If reported as L/min, skip to CO₂ equivalent calulation below).

1. If not available. MPOG will determine percentage inspired for Oxygen by subtracting Nitrous Oxide percent inspired value from 100.
2. Calculate the total Fresh Gas Flow by dividing Oxygen flows (L/min) by Oxygen percent.
3. Calculate Nitrous flow by subtracting Oxygen flows (L/min) form total Fresh Gas Flow.

Please note: In rare cases where both nitrous oxide and air are delivered, MPOG adjusts these steps to include both air and oxygen in these steps (instead of just oxygen alone).

CO₂ Equivalent Calcuation (N₂O):

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 

*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).

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

*This measure will include valid MPOG cases defined by the Is Valid Case phenotype.

Not applicable

All provider(s) signed in during the maintenance phase of a case. See ‘Other Measure Build Details’ section for algorithm for determining measure start and end times.

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