LIGHTER TOUCH Low-flow anesthesia is appropriate for any patient receiving potent inhalational agents.

Low-flow anesthesia is a great way to speed patient discharges, save money for your facility and do right by the environment. Let's examine how low flow can benefit you and your patients, and the keys to beginning a successful program.

Why go low?
In addition to faster discharges, there are 2 other key benefits to using lower flows of anesthesia:

• Cost control. When you use 2L per minute of sevoflurane or desflurane, it costs $12 per hour. If your anesthesia providers like to run higher flows (and they're out there), you're looking at more than $20 an hour. With a limited number of inhalational gas suppliers, the market will ensure you're paying the highest price possible. Low flow is a way to get gas costs below $6 an hour.
• Environmental benefits. Any time you use less nitrous oxide and anesthetic gases, you release less greenhouse gas. Sure, it's a very small amount to keep out of the atmosphere, but (a) it's the responsible thing to do and (b) if you want to market your facility as "green," using low flow when appropriate helps you be truthful about that selling point.
• Faster recoveries. This is the biggest factor: Low-flow anesthesia keeps your patients warm. The higher the gas flow rate, the more body heat is lost. This is because dry inhalational gases need to be humidified, and the water vapor that's used takes body heat with it as it's exhaled. Low-flow anesthesia preserves the body's heat, making it especially useful in longer procedures, in which normothermia is a major challenge and objective.

Low-flow anesthesia is appropriate for anyone who's a candidate for potent inhalation agents. Typical low-flow applications include extensive gastroplasties, cosmetic and plastic surgeries, urology (such as vas deferens reconstructions) and GYN. Low-flow anesthesia can even be used for longer pediatric cases, a patient population for whom maintaining normothermia is a huge issue.

LOWER LIMIT
When Does Flow Become Low?

DANGER ZONE Delivering less than 500ml of anesthetic gas per minute demands careful patient monitoring.

Low-flow anesthesia is anything less than 500ml of anesthetic per minute traveling through the gas circuit. Minimal flow — generally considered the sweet spot — is just above 500ml per minute. But you can go even lower, below 500ml per minute, which requires very accurate monitoring of the gas analyzer, pulse oximeter and capnograph.

Below 500ml per minute, the anesthesia provider has to be extremely vigilant in watching for changes. The gas analyzer itself removes about 200ml from the gas circuit every minute — so if you're putting only 500ml into the patient, you're losing 40% of it. You have the option of taking the exhaust gas from the analyzer and feeding it back into the circuit for a little extra, but most providers (myself included) just vent the exhaust gas. Above 500ml per minute, so long as everything goes as planned, you can achieve low flow without the same continuous scrutiny of monitors and patient status.

— Clifford Gevirtz, MD, MPH

When it matters most
Low-flow anesthesia is most appropriate in operations lasting longer than an hour. In ambulatory surgery, the longest procedures can extend past 4 hours. During these cases it's most difficult to maintain normothermia. But when you do, patients will wake up faster and reach discharge criteria more readily. These needs are especially pressing in freestanding centers, which often have a closing time and can't afford to pay nurses to wait after hours for patients to reach the right body temperature and become alert.

Low flows can be applied to any of the inhalational agents. As mentioned, dialing back the gas can cut sevoflurane and desflurane costs significantly. Both agents clear quickly from the cells of the body after surgery, so you have a win-win with faster post-op awakenings. Using the low-flow method with less expensive gases might not be as advantageous. Yes, you put fewer anesthetic molecules into the patient, which can ease the post-op recovery process, but the body still takes a longer time to blow off cheaper agents, which are often characterized by longer-lasting effects. So you might save $10 a case by using low-flow isoflurane, for example, but if you have to keep a nurse on overtime or tie up a post-op bed on a busy morning while patients recover, you've lost that cost advantage, and then some.

Launching low flow
It's essential that providers delivering low-flow anesthesia work with gas analyzers, pulse oximeters and capnographs that are calibrated on a regular basis — even a 10% error can result in disaster (see "When Does Flow Become Low?"). If you're going to pursue a low-flow program, don't scrimp on your bioengineering services. Follow the exact letter of each of the manufacturer's recommendations for maintenance.

You'll also need an anesthesia department or service that's eager to participate and innovate both clinically and financially. Providers interested in improving care and cutting costs should thoroughly explore the informative "Gas Man" website (see "Effective Low-Flow Training") to ensure the low-flow program they launch is safe and effective.

Selling surgeons on low flow is easy if you focus on the positives. When you tell them patients won't be retching and vomiting in recovery, that they won't have to wait 3 hours to speak to patients and their caregivers before they can leave for the day, they'll warm to the idea. After that, it's up to anesthesia providers and their monitors to deliver lower gas flows safely, so you enjoy lower overhead costs, nurses recover patients faster and surgeons see better outcomes. OSM

GAS MAN
Effective Low-Flow Training

EXPERT ADVICE Providers interested in adding low-flow skills should learn from James H. Philip, ME(E), MD.

If your anesthesia providers are interested in starting a low-flow program, point them first in the direction of a talk and tools developed by James H. Philip, ME(E), MD, an engineer based at Harvard University in Boston.

"Gas Man" is an amazing online resource for residents to learn anesthetic uptake and distribution. Experienced providers can also simulate and experiment with new methods of administering anesthesia, such as low flow, before they use them live. It's a practical and easy-to-use clinical tool, in my experience.

If you're trying to introduce low-flow anesthesia into a department in which it's never been done before, have the providers check out the website. They'll learn what to look for when things aren't going well, and how to maintain anesthesia levels and the like, so they understand the science behind the technique before implementing it in practice.

— Clifford Gevirtz, MD, MPH

On the Web

• Gas Man: www.gasmanweb.com
• "Low Fresh Gas Flow Oxygen and Agent Considerations" by James H. Philip, ME(E), MD: tinyurl.com/kybbrqx