Inhaled anesthetics are necessary agents in the operating room, yet only about 5 percent of anesthesia gas administered during surgery is actually metabolized by a patient. The other 95 percent is released into a tube as a patient exhales and vented into the atmosphere through a scavenger system. Such waste becomes greenhouse gas, accounting for about one-third of any surgical procedure’s carbon footprint and 5 percent of total hospital emissions.
Adding insult to injury, exhaled anesthetic gases remain in the atmosphere for a long time, impacting the environment until they break down completely, according to a study by Jodi Sherman, M.D., assistant professor of anesthesiology at Yale School of Medicine.
Consider the atmospheric lifespan of these inhaled gases:
• Sevoflurane 1.1 years
• Isoflurane 3.2 years
• Desflurane 14 years
• Nitrous oxide 114 years
On a case-by-case basis, the impact may seem minimal. But that’s the wrong way of looking at it, says Bryan Sabbe, M.D., division chief of anesthesia at TriStar Centennial Women’s Hospital and The Children’s Hospital at TriStar Centennial in Nashville, Tennessee, and a HealthTrust Physician Advisor.
“There are many things we can do in our lives to help curtail changes in the atmosphere and spending 10+ hours a day delivering sustainable anesthetics would certainly help limit our environmental footprint,” he says.
The American Society of Anesthesiologists (ASA) is leading efforts to reduce the carbon footprint of anesthesia gases. Its Environmental Task Force created a sustainability checklist, outlined in “Greening the Operating Room and Perioperative Arena: Environmental Sustainability for Anesthesia Practice.”
The checklist features several strategies for reducing emissions without compromising patient care, including:
• Utilizing low, fresh gas flows
• Avoiding the use of high-impact inhaled anesthetics, including desflurane and nitrous oxide
• Using intravenous and regional techniques, when appropriate
• Investing in waste trapping and/or waste destroying technology for the anesthesia equipment
Last year, the organization also launched an “inhaled anesthetic challenge,” asking hospitals to reduce facility-wide inhaled anesthetic carbon emissions 50 percent by the year 2020.
Sherman, who co-chairs the ASA’s environmental task force, has dedicated her research at Yale to quantifying the environmental impact of different anesthesia gases and techniques. In 2012, she co-published a study offering a life cycle analysis for the four inhaled agents named previously.
The study looked at the impact of these agents from cradle to grave—including manufacturing, delivery and disposal—and concluded that desflurane had the biggest impact: 15 times that of isoflurane and 20 times that of sevoflurane when delivered with 1L/minute of fresh gas flow (FGF). FGF is the amount and combination of gas (air, oxygen, nitrous oxide) that gets mixed with the anesthetic gas during the delivery of an inhaled anesthetic.
The study also indicates that greenhouse gas emissions increased significantly when all three drugs were administered with a FGF of 2L/minute, which produces a greater quantity of waste gas entering the scavenging unit and ultimately the atmosphere.
Findings like these help anesthesiologists like Sabbe choose the best gas for each procedure. For short cases and those requiring a laryngeal mask airway, sevoflurane is his agent of choice. “It does require a higher FGF, but typically nitrous oxide is not used in these cases, so that helps offset it,” he says. For longer procedures and cases where an endotracheal tube is used, Sabbe prefers isoflurane, explaining that, “The FGF can be kept very low and it has the lowest carbon footprint if FGF is kept below 1 L/min.”
To minimize desflurane use, Sabbe recommends removing desflurane vaporizers from anesthetic machines and requiring special requests for their use—or removing the drug from the formulary altogether. Removing nitrous oxide tanks from anesthetic machines, except in locations where pediatric anesthesia will be administered, is a similar tactic.
HealthTrust is also advocating clinical strategies that will lead to a reduction in overall anesthesia gas unit utilization. “This can help our members lessen their environmental impact and cost burden,” adds Patrick Greene, PharmD, HealthTrust director, negotiations and special projects. “A facility can shift utilization from desflurane, which has a longer atmospheric lifespan and larger carbon footprint, to an agent like sevoflurane. They will also see cost savings in choosing the more environmentally friendly sevoflurane.”
There are several strategies to minimize FGF beyond choosing an anesthetic gas that requires a lower FGF, as each patient and anesthetic gas choice has a minimum amount of FGF to safely deliver the anesthetic, Sabbe explains.
“The underlying question is, ‘What is the minimum safe level of fresh gas flow?’ ” he says. “You have to supply enough oxygen to satisfy the patient’s oxygen consumption while accounting for removal of gas through the sampling system and unnoticed leaks in the circuit.”
In order to match FGF as closely as possible to what the patient is actually consuming and to pinpoint the minimum-safe FGF, continuous monitoring of inspired and expired oxygen concentration is required.
The ASA’s Environmental Task Force report delineates that high fresh gas flow is only necessary with a rapid change in the concentration of anesthetic gas—usually during induction or emergence. “Once the desired concentration of anesthetic vapor has been established in the circuit, it is possible to reduce the fresh gas flow,” the task force report outlines. “The maintenance phase of a procedure is often the longest part of the procedure and typically does not require rapid changes in gas concentrations. The maintenance phase, therefore, is the best opportunity to minimize fresh gas flows.”
As with most sustainability programs, opportunities exist to increase adoption and implementation. Provider education, Sabbe suggests, is probably the most significant.
“As anesthesia providers, our practice is focused on vigilance, patient safety and leadership in the OR,” he says. “Sustainability requires both changes to and adoption of new practices by those delivering the anesthetic, which may differ from their current day-to-day routine.”
How can supply chain leaders get providers thinking about the environmental impact of anesthesia gases? Sabbe points to several resources that can help spur conversation. These include an anesthesia carbon calculator and participation in the ASA’s Inhaled Anesthetic Challenge 2020. As part of the challenge, participating facilities can anonymously pool their annual procured volume of inhaled anesthetics and receive a report detailing their carbon footprint.
“Any single case does not produce that much waste,” Sabbe says. “But that small number multiplied by the thousands of anesthetics given daily in various facilities across the country and around the world has a huge environmental impact.”