Episode #232 Embracing Safety and Sustainability in Anesthesia Care

Hello and welcome back to the Anesthesia Patient Safety Podcast. My name is Alli Bechtel, and I am your host. Thank you for joining us for another show. Is there a leak in your anesthesia machine? Have you recently changed the CO2 absorbent canister? Do you have a manual resuscitation device, auxiliary oxygen supply, and IV anesthetics immediately available? That way you can keep your patient safe while you figure out why your machine is failing all of a sudden. If you tuned in last week, then you already know that we are going to due a quick inspection of the CO2 canister to determine if that is the source of the new leak. Stay tuned because we are returning to our Rapid Response to Questions from our Readers all about replacement of the CO2 absorbent during surgery and the risk of hypoventilation today!

Before we dive into the episode today, we’d like to recognize Medtronic, a major corporate supporter of APSF. Medtronic has generously provided unrestricted support to further our vision that “no one shall be harmed by anesthesia care”. Thank you, Medtronic – we wouldn’t be able to do all that we do without you!”

We are continuing our Rapid Response show today.  Our featured article is from the October 2024 APSF Newsletter. It is, “Replacing CO2 Absorbent During Surgery – The Risk of Hypoventilation Continues” by Yuki Kuruma. To follow along with us, head over to APSF.org and click on the Newsletter heading. The first one down is the current Newsletter. Then, scroll down until you get to our featured article today. I will include a link in the show notes as well. If you haven’t done so already, check out last week’s episode, #231 for PART 1.

Last week we talked about this type of clinical scenario:  Imagine that you perform an uneventful mid-surgery change of the CO2 absorbent canister without any initial problems. Then, at the end of the procedure, you change to manual ventilation the breathing bag collapses completely and can not be re-inflated despite maximum fresh gas flow and repeatedly pressing the oxygen flush valve. When all is said and done, a large hole in the absorbent canister is discovered which caused the massive leak and inability to create pressure in the circuit. We reviewed several different types of ventilators including the piston-type breathing circuit with its unique fresh gas decoupling valve, the turbine-type ventilator, the ascending bellows ventilator, and the volume reflector ventilator. Check out Figures 1, 2, 3, and 4 for schematics of these different types of ventilators and the impact of a defective canister on the circuit.  And now it’s time to jump back into the article.

Why do we change the canister during the procedure and not before starting the case when we know that the leak will be detected during a preoperative leak test on the anesthesia machine? Well, using the entire CO2 absorbent and only changing it when there is inspired CO2 present in one of the ways to decrease the environmental impact of anesthesia care when using a circle anesthesia system at reduced fresh gas flows. At the author’s institution, the team has decided that the risk of patient harm in case of a ventilator failure outweigh the benefits at this point. They inspect the color change on the absorbent and replace the canister when needed prior to the start of anesthesia care. Then, a leak test is performed after the canister replacement to ensure that no leaks are present. Kuruma tells us that they have not been able to take full advcantage of the CLIC adapter on the Drager anesthesia machine.

And this problem of inability to detect a defective canister leading to difficult or impossible ventilation is not unique to Drager anesthesia machines. This may be a problem in all modern anesthesia machines.  There is a call to action for manufacturers whose machines allow for absorbent changes while the ventilator is in use to warn end-users about the risk of an undectected canister leak and the problems likely to result depending on the circuit design. This warning may be added to the instructions for use. Here is the example that the authors created in the case of the Drager piston ventilators:

“WARNING: Replacement of a CLIC disposable CO₂ absorbent canister during a procedure has the attendant risk of impossible manual ventilation if the replacement has an undetected leak. Due to the FGD valve, mechanical ventilation will not be altered significantly if there is a canister leak. Visual inspection of the canister is essential to detect any defect of the disposable canister before replacement. After intraprocedure canister replacement, tidal volume and inspiratory pressure as well as gas concentrations in the circuit should be carefully monitored for any changes. A manual resuscitation device, auxiliary oxygen supply and intravenous anesthetics should always be readily available to prevent patient injury in the event of an anesthesia machine failure.”

Thank you so much to Kuruma for highlighting this critical threat to anesthesia patient safety. Let’s turn our attention to the response from the Editor, Jeff Feldman on Intraprocedure Replacement of CO2 Absorbent Canisters.

Feldman provides some additional background information about the circle anesthesia system and the environmental impact. Benefits of the circle anesthesia system include decreased waste of inhalation agents and greenhouse gas emissions by allowing for reduced fresh gas flows, which leads to rebreathing of exhaled anesthetics. This means that carbon dioxide absorption is necessary to safely and effectively reduce fresh gas flows. Enter our carbon dioxide absorbents, which have their own environmental footprint that reduces the advantages from using fresh gas flows. Keep in mind that the net benefit is in favor of reducing fresh gas flows. This means that to maximize the benefits of reduced fresh gas flows and minimize the waste of any unused CO2 absorbent, it is important to continue to use the absorbent until it is no longer absorbing CO2. You can determine this when inspired CO2 appears on the capnogram. Another consideration is that this new practice only works if your anesthesia machine allows for absorbent canister replacement while in use.

Have you inspected your CO2 canister recently? It usually comes in a container made of plastic and filled with absorbent material with engineered adapters that are unique to each anesthesia machine manufacturer. The plastic canister may be damaged during shipping or stocking or even if it is dropped on the way to the operating theatre. If you change the canister and then perform the pre-use machine checkout, either automated or manual, this should detect any leaks in the absorbent canister. Unfortunately, during the procedure, it is not possible to perform a leak test while still providing anesthestic delivery and ventilation to the patient. Thus, the intra-procedure leak test involves visual inspection of the canister and vigilance once the change has been made.

Feldman notes that the Instructions for Use Manual is not always read by the end-user anesthesia professionals so merely having a warning here may not prevent continued problems. He offers some addition suggestions for steps that anesthesia professionals can take in the operating room during an absorbent canister change to help identify a leaky canister and prevent patient harm.

• “Before replacing the canister, inspect the new canister for any signs of damage or cracking. If any are present, select another one from inventory.
• After replacing the canister, reduce fresh gas flow and provide several manual breaths by squeezing the reservoir bag and observing the monitored values for inspiratory pressure and delivered tidal volume. If it is difficult to create the desired pressure or deliver the intended tidal volume, a leak in the canister should be suspected. This procedure should be useful for all anesthesia machine designs since manual ventilation is impacted similarly in all of the machines.
• Increase fresh gas flow for a few minutes after the integrity of the canister is confirmed and monitor the gas concentrations in the circuit to foster the mixing of desired gas concentrations inside the new canister.”

Feldman provides some additional considerations for being proactive to make sure that the CO2 absorbent canisters are intact.

• “Perform a leak test on a supply of absorbent canisters using an anesthesia machine and store these tested canisters in a protected box to be available for replacement.
• Develop a device that can be used to pressure test a canister before it is placed into service. Since the intraoperative change adapters are standardized for each manufacturer, the companies are well positioned to design a pressure testing device that could reside in a supply room for testing a replacement before it is used.”

Keep in mind that the goal is not to discourage you from the practice of intraprocedure absorbent replacement. There are important benefits for decreasing waste and cost, but anesthesia professionals need to be aware of the risk of a canister leak. The practical steps that we discussed can help to decrease patient risk. Feldman leaves us with this call to action for manufacturers of these canisters that are designed for intraoperative replacement to provide an appropriate warning, offer recommendation for best practices for detecting leaks, and develop methods for testing canisters for leaks before they are placed into service.

It’s time to hear from several representatives from Drager, David Karchner and colleagues. The collaboration between anesthesia professionals and industry representatives is so important for safe anethesia care. Here we go. Dear Editor. The first consideration is that sustainable anesthesia practices are important. Maximizing use of the CO2 absorbent which may involve an intraoperative canister replacement can help to minimize waste.

If we look a little closer at the Drager anesthesia machines, you can choose the traditional “loose fill” CO2 absorbent which are always refilled when the machine is not in use leading to discarding un-used absorbent material. The other option is the “CLIC” canister which allows for canister replacement during a procedure when there is evidence that the absorbent has been fully utilized such as an elevated inspired CO2 level. It is important for anesthesia professionals to be aware that the absorbent canister is part of the breathing system and a leak in the canister may lead to inability to ventilate and this is not unique to Drager machines.

The authors report that warnings and additional information have been included in the different instructions for use of Drager anesthesia machines and for the CLIC absorber. Check out Figures 1-3 in the article. Here is the warning for the CLIC adaptor:

“Disposable CLIC absorber (Optional)
The disposable absorber can be replaced during operation. The valve in the mounting ensures that the breathing system remains tightly sealed when the absorber is removed.

Note: Since a leak test cannot be performed during operation, no leak and compliance information on the changed absorber is available. Greater attention is required during operation.

Replace the disposable absorber to ensure continuous CO2 absorption in the breathing system.”

Another important consideration is that the Drager machines have monitoring devices and associated alarms to help identify problems stemming from intraoperative placement of a leaky absoprbent canister. These include gas concentration monitoring and breathing circuit pressure and volume alarms. The authors close with this:

“We thank Yuki Kuruma, again for bringing the risk of intraprocedure canister exchange to the attention of the anesthesia community and to our attention as a manufacturer. With this information, we as the manufacturer can continuously improve and update our IFU of the relevant medical devices and support users to be better prepared to avoid patient harm.”

This has been an incredible two part rapid response series. Thank you so much to Kuruma, Feldman, and the representatives from Drager. We hope that this increases awareness of this threat to anesthesia care along with providing some practical and easy to implement suggestions for how to identify leaky canisters prior to or immediately after replacement to help minimize the risk for patient harm.

Have you performed a canister replacement during surgery recently? How did it go? Were you able to follow the steps that we outlined on the show? We hope that this is helpful for your anesthesia practice going forward.

If you have any questions or comments from today’s show, please email us at [email protected]. Please keep in mind that the information in this show is provided for informational purposes only and does not constitute medical or legal advice. We hope that you will visit APSF.org for detailed information and check out the show notes for links to all the topics we discussed today.

How would you like some APSF gear? We have all-new APSF branded vests. You could stay warm while showing your support for the ASPF just by making an annual recurring contribution of $250 or more to the APSF. That’s right individuals making annual recurring contributions of $250 or greater will receive a free APSF vest. Plus, these contributions are listed in the quarterly publications of the APSF Newsletter and on the APSF website. Check out the Donors page over at apsf.org under the donors heading and I will include a link in the show notes. Just think you could be wearing an APSF vest while listening to the Anesthesia Patient Safety Podcast.

Until next time, stay vigilant so that no one shall be harmed by anesthesia care.

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