The Benefits of Low-Flow Anesthesia

Financial Management Environmental Stewardship Anesthesia

By: Joe Paone | Senior Editor

Published: 11/16/2021

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Surgical facilities can save money and the environment by using less anesthetic gas during surgery.


RELATIVE HUMIDITY By using low flows of anesthesia gases, anesthesia providers are better able to keep the patient’s airway moist.

Anesthesia providers who dial back the anesthetic gases could save your facility money and go greener. The idea behind low-flow anesthesia is quite simple: Adjusting flows of inhalational agents to a “just right” level of administration benefits the patient because, with less fresh gas flowing, humidity is better maintained in the airway. The practice also limits the amount of gas that’s used and waste that must be scavenged, making it a safe, environmentally friendly and fiscally responsible choice.

“Among anesthesiologists, low-flow anesthesia is known and used intermittently,” says Beverly Philip, MD, FACA, FASA, immediate past president of the American Society of Anesthesiologists (ASA). “What is coming to the forefront now are the reasons why it should be used. The patient care advantages have been known for some time, but the issue of needing to conserve costs is becoming more important, as is concern about the environment. The ‘why bother?’ has become more prominent.”

Why bother? There are several reasons to go low with anesthesia flows.

• Precise sedation. Hilary Stambaugh, DNAP, CRNA, a staff nurse anesthetist with a private anesthesia group in Tulsa, Okla., says the four anesthesia gases commonly used today are sevoflurane, desflurane, isoflurane and nitrous oxide, with the first two — especially the less expensive sevoflurane — administered frequently at outpatient surgery centers.

Low-flow techniques work with any anesthetic gas if the anesthesia provider administers them knowledgably, according to Dr. Stambaugh. “If you carefully titrate gases,” she says, “you can make them all act the same.”

The flow range can vary from 0.5 to 12 liters per minute. “The effect on the patient is the same whether you’re administering 0.5 or 12 liters per minute,” says Dr. Stambaugh. “You get the same level of anesthesia if you’re using really high flows or a more conservative approach that uses less gas and less volatile anesthetic, which means less gets vented out to the atmosphere after the patient exhales it.”

The lower you set the carrier gas, the better you save on the patient’s humidification, and on the cost-per-hour of the drug you use, according to Dr. Philip. “I have used lower flows for a long time, typically half-liter a minute, for all those reasons,” she says.

Many anesthesia providers, out of clinical belief or forgetfulness, often use more gas than is necessary. Alicia Edmonds, DNAP, CRNA, a practitioner at Dartmouth Hitchcock Medical Center in Lebanon, N.H., says many providers cut their teeth at the start of their careers on older, less precise anesthesia machines, as well as gases that have since fallen out of favor because of their causticity. “You now have a population of anesthesia providers who are still in that mindset of, ‘You need higher flows to be able to get anesthesia onset.’”

“Providers often start with administering flows in the two to five liter a minute range,” says Dr. Philip. “The higher flow rates are left over from administering anesthetics we don’t even use anymore.”

Another common scenario is not adjusting flows during the procedure. “One of the biggest barriers to low-flow anesthesia is providers simply sticking with the flow rate set at the beginning of the case because that’s easier to manage,” says Dr. Edmonds. Thankfully, digital flow meters on most newer anesthesia machines make it easy to titrate the gas to exact amounts during surgery.

Anesthesia providers can unilaterally administer less gas with the help of modern anesthesia machines and advanced patient monitoring. Dr. Edmonds says the ability to monitor oxygen saturation, end tidal CO2, blood pressure and heart rate enables less wasteful anesthesia administration. Anesthesia providers can be much more precise about how much gas they need to administer.

“The patient has a deep level of anesthesia the whole time, but I’m doing it in a smarter way,” says Dr. Stambaugh.

 

HIGH VALUE Dr. Alicia Edmonds employs low-flow anesthesia not only because it reduces costs and is clinically effective, but because it has less impact on the environment — a subject close to her heart.  |  Tung Nguyen

• Overall savings. Drs. Edmonds and Stambaugh coauthored a study on low-flow anesthesia published earlier this year in AANA Journal. The paper examined the cost savings and reduction in environmental release enabled by the technique. “Anesthesia gases on the whole are very cheap,” says Dr. Edmonds. “Most hospitals don’t even pay attention to their expense because it’s such a small blip in the overall cost of care. Our hospital alone could have saved over $50,000 a year by running low flows of anesthesia. That doesn’t seem like very much when you look at the high cost of running ORs all day, but it’s not nothing.”

To drive home the cost and waste savings benefits, surgical administrators could monitor gas usage, either in the aggregate or by individual providers. “Most anesthesia machines are sophisticated enough to track specific flows,” says Dr. Stambaugh.

Administrators could dig a little deeper and research what the gas is costing and what they could save. This analysis is powerful and can be used to approach individual providers to inform them of their current practice, present the research and data, and share the cost and environmental savings they’d realize by implementing low-flow anesthesia. “It can be mind-blowing to anesthesia providers that they can have this huge effect,” says Dr. Edmonds.

Anesthestic gases act as greenhouse gases. “They affect the atmosphere for many years, and trap more heat than carbon dioxide,” says Dr. Edmonds. “Studies have shown they contribute to climate change, and anesthesia providers are more aware of their negative effects on the environment.”

Because the benefits of low-flow anesthesia are two-pronged — saving money and saving the environment — most anesthesia professionals will be attracted to at least one cause. “Some providers respond to the cost aspect, but others say, ‘Well, it’s not coming out of my pocket, I don’t care,’” says Dr. Edmonds. “The environmental piece might be near and dear to their hearts because they exist in this world and want to preserve it.”

• Safe administration. Anesthesia providers who employ low-flow anesthesia need a comprehensive knowledge of the anesthetic drugs they use, understand the anesthesia machines they’re using at a fundamental level and monitor the amount of oxygen their patients need, according to Dr. Philip.

Dr. Stambaugh says a major component of low-flow anesthesia is gas chromatography. Anesthesia providers place a sample line that goes from the breathing circuit to the anesthesia machine. “It tells us the percent of gas the patient is inhaling and exhaling, which gives us the scientific knowledge to know the patient is going to be amnestic,” says Dr. Stambaugh. “If you think of breath as a tidal volume, the patient’s end tidal percentage of gas is measured at the end of an exhale. The gas sampling tells us the end tidal percentage. That’s how we know we’re administering low-flow safely.”

The patient has a deep level of anesthesia the whole time, but I’m doing it in a smarter way.
— Hilary Stambaugh, DNAP, CRNA

Some industry concern exists regarding the use of low-flow sevoflurane because of a breakdown product called Compound A that is produced when the gas interacts with carbon dioxide absorbents in the anesthesia machine, which are meant to scrub CO2 from the breathing circuit so the patient doesn’t rebreathe it along with a high concentration of sevoflurane.

Early studies examined whether Compound A caused kidney injuries and found that low-flow sevoflurane can produce Compound A. But multiple randomized control trials and meta-analyses of randomized control trials have yet to determine that Compound A causes any recognizable dip in kidney function.

Studies and statistics have shown Compound A is not an issue — even during lengthier cases, according to Dr. Edmonds. “We’re not saying that Compound A doesn’t exist,” she says. “We’re saying humans don’t break it down the same as has been shown in animal studies. That’s true in pediatric populations, elderly populations and populations that have a history of kidney disease.”

The CO2 absorbers that were producing Compound A are no longer in use at most facilities due to a switch from potassium hydroxide to calcium hydroxide in modern absorbers. “The CO2 absorbents available now are less reactive, and you can buy versions that are essentially nonreactive,” says Dr. Philip. “The most reactive of the CO2 absorbents haven’t been on the market for a while.”

The bottom-line question: Are clinical concessions made using low-flow technology? “Not one,” emphasizes Dr. Edmonds. 

Promoting improved care

Surgical administrators don’t need to be aware if anesthesia providers employ low-flow techniques, but they can benefit from knowing more about the practice and how it works. “If they can set up an education seminar when new anesthesia providers come on that reiterates what low flow is, how effective it is and how safe it is for the patient, more providers would be less apprehensive to do it,” says Dr. Edmonds.

“Low-flow anesthesia is safe,” says Dr. Philip. “It’s advantageous for patients, for supporting facilities by decreasing costs and for helping the environment. By using low-flow anesthesia, providers lead by showing that they can contribute to the success of the facilities in which we work.” OSM

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