Episode #112 The Past, Present, and Future of LMA Use Revisited

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. We have a special show today. It is all about an important device that is used often when providing anesthesia care and plays an important role in the difficult airway algorithm. I will give you a moment to think about what device meets this criteria, but here is a hint, we first talked about it on the podcast in December 2021.

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

Do you have your answer locked in? Are you ready? Today, we will be talking about the Laryngeal Mask Airway. This device may be used as part of the difficult airway algorithm and may also be used as part of routine airway management when providing anesthesia care. Today, we are revisiting our show from December 2021, Episode 76, “The Past, Present, and Future of LMA Use.” Our featured article today is “The Laryngeal Mask Airway: Expanding Use Beyond Routine Spontaneous Ventilation for Surgery” by Schwartz and Peng. To follow along with us, head over to APSF.org and click on the Newsletter heading. Fifth one down is Newsletter Archives. Then, scroll down until you get to the October 2021 APSF Newsletter. Then scroll down until you get to our featured article today. I will include a link in the show notes as well. We are returning to episode 76 because it is one of our most popular shows and contains important information about LMA use including indications, contraindications, and considerations for clinical practice. Plus, there is a new 2022 ASA Guidelines for difficult airway management with changes from previous guidelines. You can find more information in the June 2022 APSF Newsletter in the article, “Anesthesia Patient Safety Foundation Update: 2022 American Society of Anesthesiologists Practice Guidelines for Management of the Difficult Airway” by John Fiadjoe and David Mercier. I will include a link to this article in the show notes as well. We are going to be covering this article on an upcoming show, so stay tuned.

And now, we are returning to Episode 76 to learn about the past, present and future of LMA use. Here we go…

[EPISODE 76]

Have you placed a laryngeal mask airway or LMA recently? Was it for a routine or non-routine use? Today, we will be reviewing recent advancements of this device and the uses. Stay tuned as we discuss the risk of aspiration when using an LMA as well as using mechanical ventilation with an LMA.

Before we get into the article, we are going to hear from one of the authors. Here are the authors of this interesting article.

[Schwartz] “Hello, my name is Shawna Schwartz. I am a current cardiothoracic anesthesia fellow at the University of Florida in Gainesville. Dr. Yong G. Peng is the chief of cardiothoracic anesthesia and a professor of anesthesiology at the University of Florida.]

To get started, I asked Schwartz why she wrote the article. Let’s take a listen to what she had to say.

[Schwartz] “Due to innovation and advanced technology, the LMA has expanded its use beyond routine spontaneous ventilation for surgery. In these non-traditional ways, for example, surgeries with obese patients or in laparoscopic surgery, the LMA was being used with muscle relaxant and mechanical ventilation. Because there seems to be a lot of variability in clinical practice regarding the use of LMAs across different institutions, we were curious about the safety and efficacy of the use of LMAs beyond routine spontaneous ventilation. With these questions in mind, it inspirated us to review the literature on these complicated topics to determine if we needed to adapt our clinical practice and to share our knowledge with others.”

[Bechtel] Thank you so much to Schwartz for helping to get the show started today. The article starts off with some history. Did you know that the LMA was invented in 1983 by Dr. Archie Brain to function as an alternative airway device to the facemask and endotracheal tube? The LMA has a role in airway management since it may be able to provide better quality ventilation than the facemask as well as less instrumentation of the airway than placement of an endotracheal tube. Over the past 40 years, we have seen improved versions of the LMA from the original, LMA classic, to the LMA supreme. Let’s take a look at the LMA devices. One of the modifications that has occurred over time is changes in the oropharyngeal seal pressure or OSP with lower OSP leading to increased gastric insufflation and risk of aspiration.

First, we have the LMA classic, a first generation device made of silicone with the advantages of being used as a rescue device with less pharyngolaryngeal trauma and less respiratory problems compared to an endotracheal tube. On the downside, it has a low OSP and higher cost with processing of this non-disposable device.

Next up, we have the LMA unique which is another first generation device, but this one is made of polyvinyl chloride and is the disposable version of the LMA classic and retains the disadvantage of the low OSP.

Another LMA is the FasTrach LMA constructed of polyvinyl chloride and silicone. This device is an intubating LMA that can be used to help in situations of blind and difficult intubations. The downsides include that it is larger sized and may be difficult to place with no available pediatric sizes and increased processing cost.

During head and neck procedures, you may be able to use the LMA flexible which is another polyvinyl chloride and silicone device with wire-reinforced tubing. LMA flexible also has a low OSP and higher processing cost.

There are 2 second generations LMAs. The non-disposable LMA is the LMA ProSeal made of silicone with a gastric suction port, built in bite block, and high OSP. Keep in mind that this device is bulky and depending on positioning the gastric port may be obstructed and there is a higher cost for processing. The similar disposable second generation device is the LMA Supreme made of polyvinyl chloride.

Check out the article in Table 1 for images of the different LMAs.

Now, let’s talk about LMA use in clinical practice which may include the following advantages: ease of use and decreased airway tissue injury, hemodynamic changes, and postoperative complications compared to endotracheal tube placement. An LMA may be placed for airway management in a difficult airway as well as during general anesthesia. This device has led to improved patient safety because it may be used as part of the ASA updated difficult airway algorithm for emergency noninvasive airway access. Over 40 years of research and clinical use has shown that the LMA is safe and reliable, but some questions remain about the use of an LMA in clinical practice. These questions are important to help keep patients safe during anesthesia care with an LMA. Can an LMA be used safely with positive pressure ventilation and muscle relaxants, during laparoscopic surgery and with obese patients? Concerns about the safe use of LMAs in these non-standard clinical settings include the following: malposition and inadequate seal, airway injuries, aspiration risk, safety of mechanical ventilation, safety in obese patients.

Before we go any further and before you place another LMA, let’s take a moment for a review the absolute and relative contraindications for LMA use. The absolute contraindications include patients with the following: trauma, non-fasted, bowel obstruction, emergency surgery, and delayed gastric emptying. The relative contraindications include patients undergoing major abdominal surgery, airway surgery, laparoscopic surgery, patients positioned prone for the surgery, and patients with the following pregnancy at greater than 14 weeks, obesity with a BMI greater than 30, decreased lung compliance with peak inspiratory pressure greater than 20 cm H2O, and altered mental status.

Now, that we know when placement of an LMA is contraindicated, let’s discuss considerations for LMA placement and size and it is time for a literature review as well. LMA placement may occur following induction of general anesthesia with or without a muscle relaxant. This was studied by Hemmerling and colleagues who looked at the success rate of placement on the first attempt with muscle relaxants at 92% compared to 89% without muscle relaxant use. Considerations for the appropriate size of LMA to use is important since using an LMA that is too small may mean that there is a leak around the LMA and inadequate ventilation. If the LMA is too large, it may be difficult to position appropriately leading an inadequate seal and leak. Another concern with placing a device that is too large is the increased risk for soft tissue damage, lingual nerve injury, and pharyngeal damage especially with forceful placement. It appears that the size 4 and 5 LMAs may be used safely with a good seal for average female and male patients, respectively. The appropriate LMA size has been studied as well. If we look at the study by Asai and colleagues, who found that there were less leaks with placement of the larger LMA for males and females and that lower inflation volumes could be used to create the seal with the result of less pressure on the pharyngeal tissue. What about complications associated with LMA use? Let’s take a look at the study by Bimacombe and colleagues published in Anesthesiology in 2000. This group studied 300 patients who reported pharngolaryngeal complaints following LMA use during surgery. The results revealed that there was a higher incidence of sore throat and dysphagia in patients who had an LMA placed with high cuff volumes compared to LMA use with low cuff volumes. Higgens and colleagues evaluated the risk for sore throat with endotracheal tube compared to LMA placement in a prospective study with over 5,000 patients. The incidence of sore throat was 45.4% in patients who had an endotracheal tube placed compared to 17.5 % in patients with an LMA. Even when patients have an LMA placed rather than an endotracheal tube, they may still be at risk for pharygolaryngeal complications and this remains a threat to anesthesia patient safety. Stay vigilant to use the appropriate LMA size and minimize intracuff volume.

Another considerations for clinical practice is when to remove the LMA, awake or under deep anesthesia. The Cochrane review by Mathew and colleagues in 2015 included 15 randomized controlled trials and over 2,000 patients with LMA classics placed. The authors reached the conclusion that there was not sufficient evidence to determine the superiority of either time for removal of the LMA, but they also note that the quality of evidence was low or very low and there is a need for further investigation. Removal of the LMA in awake patients may be associated with coughing or bucking or significant hemodynamic changes while removal in patients under deep anesthesia may be associated with snoring or airway obstruction requiring intervention. It is important to weigh the risks and benefits of the timing of LMA removal to help keep patients safe during this crucial time.

We are almost out of time for today and we still have more to discuss in this article. Plus, we are going to hear from Schwartz again about the future of LMA use. Before we go, let’s take a minute to review Table 2 from the article which includes a nice summary about the use of LMA for non-standard clinical practice.

Here we go:

1. Using an LMA with mechanical ventilation compared to spontaneous ventilation. The concerns here include the increased risk for gastric insufflation and aspiration when high inspiratory pressures are used as well as the inability for self-regulation of the anesthesia depth that occurs with spontaneous ventilation. The authors conclude that adequate ventilation is possible with different modes of ventilation and it is important to minimize inspiratory pressures.
2. Use of muscle relaxants combined with LMA use in combination with mechanical ventilation. This may provide a benefit for LMA placement and be beneficial for certain surgeries.
3. LMA use during laparoscopic surgery. Remember, this is a relative contraindication and the concern includes the increased aspiration risk due to peritoneal insufflation. However, the use of an LMA for these surgeries may be considered in fasted patients and with second generation LMAs.
4. LMA use with obese patients. This is also a relative contraindications with the concern for decreased pulmonary compliance and inadequate ventilation. The LMA may be necessary as a temporary rescue device in obese patients with a difficult airway and may be appropriate for some obese patients, but additional studies are needed to evaluate the use of LMAs in morbidly obese patients during surgery with general anesthesia.

Thank you for tuning in for our special LMA revisited show. For more information about non-standard clinical practices and LMA use, check out Episode #77, “Keeping Patients Safe During Anesthesia Care With an LMA. 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.

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