Episode #155 Depth of Anesthesia Monitoring and the Argument Against Supraglottic Airway Devices for Laparoscopic Surgery
June 20, 2023Welcome to the next installment of the Anesthesia Patient Safety podcast hosted by Alli Bechtel. This podcast will be an exciting journey towards improved anesthesia patient safety.
Today’s episode is an Articles Between Issues Episode. That’s right, we are going to be talking about some of the dynamic articles that were published in between newsletter releases.
First, we are going back to the March 12th, 2023, article, “Response to APSF Updated Monitoring Recommendations – EEG to Assess Anesthetic Depth” by Donald Lambert.
Here are the citations to the articles mentioned on the first part of the show today:
- Lambert DH. A proposed method to minimize acute kidney injury by avoiding vasopressors during surgery. Renal Failure. 2022;44(1):1993-1995. doi:10.1080/0886022X.2022.2141647
- https://www.apsf.org/article/depth-of-anesthesia-monitoring-why-not-a-standard-of-care/
Are you using an EEG-based monitor for every patient? These are very important considerations for keeping patients safe from hypotension and end-organ damage as well as from awareness during anesthesia care.
- The depth of anesthesia results from a combination of inhalational and intravenous agents
- The combined effect is not reflected by calculating the MAC value of the inhaled agents.
- An EEG-based monitor is currently the only way to assess the combined effect of anesthetic medications on the patient.
- Maintaining a proper anesthetic depth based on EEG monitoring, can result in a MAC value < 0.7 MAC without risk of awareness and may positively impact patient outcome.
Our next article is “CON: Supraglottic airway devices: Safety concerns in laparoscopic surgery” by Sabastian Omenyo and Laura Duggan published on May 2, 2023.
Check out this Interview with Dr. Archie Brain for the full story about the invention and development of the Laryngeal Mask Airway from the Association of Anesthetists. https://anaesthetists.org/Home/Heritage-centre/Collection/Oral-Histories/Dr-Archie-Brain-The-Laryngeal-Mask
Conversion to endotracheal intubation may be required in the setting of ineffective ventilation and gastric insufflation. We review the steps to help optimize the conditions in this emergent situation.
- Turn om the room lights.
- Call for help
- Reposition the patient for airway management.
- Remove laparoscopic instruments.
- De-sufflation of the abdomen
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© 2023, The Anesthesia Patient Safety Foundation
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 are so excited about this show today for a couple of reasons. First, the June 2023 APSF Newsletter is here. We are working behind the shows to bring you all new shows based on these great new articles with exclusive content from the authors. But before we get to the June 2023 APSF Newsletter, we have more new content that we need to discuss.
But before we dive into the episode today, you’ve heard me recognize our corporate supporters on this show, but there’s another supporter who is absolutely essential – YOU! Every individual donation matters so much. Please visit APSF.org and click on the Our Donors heading and consider making a tax-deductible donation to the APSF.
Today’s episode is an Articles Between Issues Episode. That’s right, we are going to be talking about some of the dynamic articles that were published in between newsletter releases. First, we are going back to the March 12th, 2023 article, “Response to APSF Updated Monitoring Recommendations – EEG to Assess Anesthetic Depth” by Donald Lambert. To follow along with us, head over to APSF.org and click on the Newsletter heading. Second one down is the Articles Between Issues. From here, scroll down until you get to our featured article. This article is a letter to the Editor in response to the APSF’s Committee on Technology updated monitoring recommendations for preventing awareness during general anesthesia. We talked about these monitoring recommendations on the 100th Episode of this podcast, so if you haven’t listened to that, make sure. You check it out. I will include a link to the original article and the podcast episode in the show notes as well.
Lambert highlights some important points from the APSF updated recommendations to set the stage, which included the following:
- Whenever an inhaled agent is administered, its end-expired concentration shall be measured, and a low concentration alarm be activated if available.
- Whenever a neuromuscular blocking agent is administered during inhalational anesthesia, if 0.7 MAC cannot be maintained, an EEG-based monitor of anesthetic depth should be used and an inadequate anesthetic depth alarm limit set if available.
- Whenever a neuromuscular blocking agent is administered during total intravenous anesthesia (TIVA), an EEG-based monitor of drug effect is recommended, and alarm limits activated when available.
The APSF recommendations also discussed that for patients with hemodynamic compromise who could not be maintained with an inhaled anesthetic concentration of 0.7 MAC, monitoring for the risk of awareness is important and an EEG-based monitor for anesthetic depth may be considered to make sure the patient remained at an adequate depth of anesthesia.
Now, let’s talk about Lambert’s response. He starts by providing some critical information about awareness during general anesthesia and the risks of myocardial injury and acute kidney injury. Keep in mind that awareness is extremely rare, but may have significant complications including post-traumatic stress disorder, sleep disturbances, and anxiety. The risks of myocardial injury following non-cardiac surgery and acute kidney injury due to hypotension and vasopressor administration are more common complications during general anesthesia. Hypotension requiring vasopressor administration may occur during the time between anesthesia induction and surgical incision due to the lack of patient stimulation. Vigilance is required to provide adequate depth of anesthesia and avoid hypotension and end-organ injury. Remember, in the APSF recommendations, a MAC of 0.7 is recommended to prevent awareness. This MAC value of 0.7 was set in the setting without supplemental IV medications. It is important to consider the effects of maintaining a MAC of 0.7 in the clinical setting with additional IV medication administration which may include propofol, ketamine, opioids, and benzodiazepines. This may lead to a greater depth of anesthesia as well as an increased risk for hypotension, vasopressor use, and possibly myocardial injury and acute kidney injury. Lambert asks this important question: “Why not use an EEG-based monitor in all patients and allow MAC to vary according to the patient’s wakeful state, as determined by the EEG-based monitor and the mean arterial pressure?” Check out Lambert’s article, “A proposed method to minimize acute kidney injury by avoiding vasopressors during surgery” published in Renal Failure in 2022 for more information about achieving the goals of avoiding awareness and hypotension without vasopressors during general anesthesia. I will include the citation in the show notes as well.
Lambert highlights the reliance on end-tidal agent monitoring and MAC levels as a way to determine the patient’s level of consciousness and help prevent awareness. The depth of anesthesia and absence of awareness depends on more than the minimum alveolar concentration or MAC value. Additional considerations include administration of the combination of IV and inhaled agents and the combined effects on awareness and hemodynamics.
Perhaps, an EEG-based monitor should be considered as the standard of care for monitoring depth of anesthesia. Check out the October 2019 APSF Newsletter article by Jin and colleagues, “Depth of Anesthesia Monitoring—Why Not a Standard of Care?” I will include a link in the show notes as well.
Lambert leaves us with some important points to consider:
- “The depth of anesthesia results from a combination of inhalational and intravenous agents
- The combined effect is not reflected by calculating the MAC value of the inhaled agents.
- An EEG-based monitor is currently the only way to assess the combined effect of anesthetic medications on the patient.
- Maintaining a proper anesthetic depth based on EEG monitoring, can result in a MAC value < 0.7 MAC without risk of awareness and may positively impact patient outcome.”
Are you using an EEG-based monitor for every patient? These are very important considerations for keeping patients safe from hypotension and end-organ damage as well as from awareness during anesthesia care.
Good news! We have time to check out another article between issues. Our next article is “CON: Supraglottic airway devices: Safety concerns in laparoscopic surgery” by Sabastian Omenyo and Laura Duggan published on May 2, 2023. You can find the article by clicking on the Newsletter heading and clicking on the second one down, Articles Between Issues. I will include a link in the show notes as well. You might remember that we talked about supraglottic devices for laparoscopic surgery recently on the podcast. It was episode #143. That was the Pro-side of the debate on the use of Supraglottic Devices for airway management during laparoscopic surgery. Today, we are bringing you on the Con-side of the debate. Time to refill your coffee or tea because here we go!
The authors start the article with some history, so we are traveling back to 1986 when Sir Archie Brain patented the Laryngeal Mask Airway. He completed the first prototype in his home in London and then was actually rejected by several companies at first. Now, this device has been used over 350 million times around the world since then. He developed the device after contemplating what was missing in anesthesia practice at that time and realized that there might be a need for something in place of holding the facemask. For more information on the process of inventing the laryngeal mask airway, check out the link in the show notes for an interview with Dr. Archie Brain. It is fascinating. We now have second-generation devices that contain esophageal ports and devices designed to help with tracheal intubation through the LMA. Supraglottic airway devices have an important role in the difficult airway algorithm and may be a safe alternative to endotracheal tube placement depending on the patient and the surgical procedure. In Episode #143, we talked about the benefits of using these devices during laparoscopic surgery, but there are some significant concerns which may include the following:
- Potential risk of gastroesophageal regurgitation and aspiration
- Difficulty with effective ventilation due to pneumoperitoneum, postural changes, and increased carbon dioxide burden.
- Ability to convert to endotracheal tube placement if needed during the surgical procedure.
Let’s talk about pulmonary aspiration. This is a big threat to anesthesia patient safety. It does not occur very often as evidenced by the 115 aspiration claims from the 2,496 ASA closed claims cases collected between 2000-2014. When it does occur, there is a high fatality rate so we need to do everything we can to prevent aspiration. Of the 115 patients with aspiration, 57% died as a direct result of the aspiration event and 55% of the events occurred during elective surgery. Since aspiration is a life-threatening complication, then it is critical that the aspiration risk with supraglottic airway devices used during laparoscopic surgery be equal to or less than the risk of aspiration associated with tracheal intubation. We do not want to put patients at higher risk for aspiration by deciding to use a supraglottic airway device instead of an endotracheal tube. A cuffed endotracheal tube can protect the tracheal and lungs if there is gastroesophageal regurgitation. A supraglottic airway device with an esophageal port may be able to redirect gastric contents away from the tracheal, but may not prevent aspiration.
Since aspiration does not occur often, it would be difficult to perform a randomized trial that evaluated supraglottic airway device to tracheal intubation in elective patients undergoing laparoscopic surgery. We need to use data from closed claims, retrospective observational studies, and clinical expertise and opinion to assess the safety of supraglottic airway devices used during laparoscopic surgery. We also need to consider delayed gastric emptying and gastroparesis which may increase liquid and solid gastric contents that may lead to increased intragastric pressure. Decreased gastric motility may occur due to physiologic stresses from trauma, sepsis, pain as well as medications such as prednisone, opioids, and levodopa. We often consider patients presenting for elective surgery who have followed fasting guidelines to have empty stomachs. Investigators looked into this in 2017 by performing preoperative gastric ultrasound on 538 fasted patients before elective surgery and found that 1.7% had solid gastric matter and 4.5% had more than 1.5ml/kg of gastric fluid. Only 6 out of the 32 patients with solid gastric matter had risk factors for delayed gastric emptying. In 2020, another study of 138 fasted patients undergoing elective laparoscopic cholecystectomy found 12 patients with solid gastric matter and 6 with more than 1.5ml/kg gastric fluid. These results suggest that we may not be able to identify which patients are at risk for aspiration.
We must also think about procedural considerations with laparoscopic surgery and what happens if you need to convert from the supraglottic device to endotracheal intubation. Laparoscopic procedural considerations include the following:
- Patient positioning, with Trendelenburg or reverse-Trendelenburg which may result in displacement of the supraglottic device.
- Dark room
- Patient’s head covered under the surgical drapes
- Pneumoperitoneum with increases in carbon dioxide load and ventilation requirements with restricted diaphragmatic movement
Conversion to endotracheal intubation may be required in the setting of ineffective ventilation and gastric insufflation. What does this urgent conversion look like? Have you had to do this? Let’s review the steps to help optimize the conditions in this emergent situation.
- Turn om the room lights.
- Call for help
- Reposition the patient for airway management.
- Remove laparoscopic instruments.
- De-sufflation of the abdomen
Keep in mind intubation may be difficult or impossible if there is head and neck swelling from prolonged Trendelenburg positioning. Another threat is the timing of the conversion during a critical part of the surgery in case there is bleeding or it is not possible to stop the procedure. The authors tell us that these situations can be avoided by performing tracheal intubation under a controlled situation right from the very beginning.
The authors remind us that fasted patients may present for elective surgery with significant gastric contents and there are additional concerns for aspiration including patient positioning, obesity, and other patient comorbidities. There is a call to action for anesthesia professionals to know the oropharyngeal leak pressure for each supraglottic device that they use. You can find this in the manufacturer’s’ instructions for use. When deciding on your plan for airway management, it is important to consider your back up plan for conversion to tracheal intubation which may be quite challenging. Supraglottic devices have an important role for airway management during anesthesia care, but the safety of using these devices for laparoscopic surgery is not known. The authors conclude that widespread adoption of supraglottic airway devices for laparoscopic procedures is not supported.
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.
It is June and that means that the all-new June 2023 APSF Newsletter is here! We are so excited to talk about the new articles with exclusive content from the authors right here on this podcast in the upcoming weeks!! In the meantime, we hope that you check out the new newsletter. Plus, this is a good time to make sure that you subscribe to the APSF Newsletter email list which will give you expedited access by email to our current APSF Newsletter issue. So, what are you waiting for? Check out the link in the show notes and subscribe now!
Until next time, stay vigilant so that no one shall be harmed by anesthesia care.
© 2023, The Anesthesia Patient Safety Foundation