Episode #84 Keeping Patients Safe and Strong with Quantitative Neuromuscular Monitoring

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. For the past couple weeks, we have been out of the operating room to discuss important topics related to non-operating room anesthesia or NORA. We are switching gears today to talk about a piece of technology that can help keep patients safe during anesthesia care.

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

You might be thinking that I was a little vague and that there are a number of devices that we could be talking about on this podcast. Well, today we are headed back into the October 2021 APSF Newsletter to discuss Quantitative Neuromuscular monitoring. There are just so many great articles in this newsletter! Now, do you use a quantitative neuromuscular monitor? Have you ever used one? Do you use it routinely? Let us know your experience with quantitative neuromuscular monitors by tagging us @APSForg and using the hashtag #APSF podcast after you are done listening to the show today. Before we get into the article, we have exclusive, behind the scenes content from the author of the article, Ross Renew and I will let him introduce himself now.

[Renew] “Hi, my name is Ross Renew and I’m an assistant professor of anesthesiology at Mayo Clinic in Jacksonville, FL.”

[Bechtel] To kick off the show today, I asked Renew what got him interested in this topic? Let’s take a listen to what he had to say.

[Renew] “My initial interest with neuromuscular blockade management stems from an experience in residency that I had. It seems as almost it was a rite of passage to have a patient have to get reintubated due to residual weakness at some point in the PACU. I can recall using a peripheral nerve stimulator on the face and trying to give neostigmine at deeper levels of blockade. And some patients did okay but everybody got burned at least once. And seeing those kinds of avoidable complications really struck a cord with me that in my mind I was doing everything appropriate, delivering the best care that I could but we were still having bad outcomes with patients. Digging a little bit deeper in the literature and working with some of my mentors started realizing the potential benefits of utilizing qualitative neuromuscular monitors to confirm adequate recovery. A lot of the faculty that I had worked with did not have a ton of experience with some of these devices and I realize that there are some passionate experts in this field, but the large portion of the anesthesia community is unfamiliar with a lot of these devices and the potential benefit they could have with patients.”

[Bechtel] This should strike a cord with everyone interested in anesthesia patient safety, so let’s get into our featured article, “Advancements in Quantitative Neuromuscular Monitoring” by Ross Renew. 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 to October 2021. From here, scroll down looking in the right hand column until you see our featured article. I will include a link in the show notes as well!

Renew starts off the article by highlighting the role for quantitative neuromuscular monitoring since it is the only reliable monitor to assess recovery from neuromuscular blockade and prevent postoperative residual weakness and further complications. Anesthesia professionals must be able to use these monitors to help keep patients safe following administration of neuromuscular blocking drugs. The article continues with a compelling reason to utilize quantitative neuromuscular monitors. Consider the scenario of a hypotensive patient in the operating room. The anesthesia professional quickly acts to treat the low blood pressure with IV fluids or vasoactive medications. The next step involves checking the blood pressure again to ensure that normotension has been restored. We use non-invasive blood pressure cuffs or intra-arterial lines to accurately and reliably monitor blood pressure during patient care and be able to quickly determine if our treatment of either hypotension or hypertension is effective and adequate. We don’t just use our knowledge of  pharmacodynamics or subjective assessments such as checking a pulse in place of real-time, accurate, and reliable monitors.

Monitoring neuromuscular blockade has been different in the past when only subjective assessments such as the 5-second head lift were available or later the qualitative twitch monitor which required that the anesthesiologist be able to differentiate the difference in strength of the twitches in the train of four or detect fade. With the introduction of Sugammadex, monitoring depth of neuromuscular blockade and recovery from the blockade may not even occur. The clinical situation may look like this: Administer Sugammadex to reverse the blockade, wait a little bit, then extubate the patient and head over to the recovery room. This is a recipe for complications and re-intubation. Whenever Phenylephrine is administered to treat hypotension, a repeat blood pressure is checked to make sure that the blood pressure has improved. We need to be just as vigilant with neuromuscular blockade and recovery. Renew writes, “Anesthesia professionals rely on state-of-the-art technologies to maintain homeostasis of patients and must not exclude neuromuscular blockade management from such efforts.”

So, why is it that these monitors remain in the drawer of the anesthesia machine and not on the patient? Let’s look at the literature. A 2019 article in Anesthesia and Analgesia surveyed over 2,500 anesthesiologists around the world to assess knowledge related to the fundamentals of neuromuscular blockade and the anesthesiologists’ confidence of their knowledge on this topic. Here are the results: Respondents answered only 57% of the questions correctly and the vast majority of respondents, 92%, were inappropriately confident that they had the right answer. So, there is over-confidence paired with a knowledge gap in this area. Another interesting knowledge gap relates to the belief that Sugammadex administration for reversal does not require further neuromuscular monitoring since it is fast and effective. We have talked about Recurarization with Sugammadex before on this podcast for episode 20 and 58 and I encourage you to check out those shows later. What we are learning is that with deeper levels of blockade almost 10% of patients may have residual weakness following Sugammadex administration and without neuromuscular monitoring, this would go undetected and puts patients at risk for respiratory complications and the need for re-intubation. Quantitative neuromuscular monitors remain in the drawer of the anesthesia machine or not prioritized for purchase and available wherever anesthesia care is provided due to include lack of knowledge, overconfidence, inconsistent training, and lack of easy access to and easy to use reliable quantitative neuromuscular monitors.

We hope to see these monitors become routine during anesthesia care going forward given the recent push from expert panels that have highlighted the need for routine quantitative neuromuscular monitoring and anesthesia societies have updated guidelines to include recommendations for the use of quantitative monitoring whenever neuromuscular agents are administered. To meet this need, there are new monitors available with technology that has advanced far beyond the 5-second head lift.

Let’s take a look at some of these monitors now. First up, the peripheral nerve stimulator. This is a qualitative monitor that is unable to provide accurate train of four monitoring since anesthesia professionals are unable to determine if fade is present when the train of four ratio is greater than 0.4. The use of the peripheral nerve stimulator to monitor neuromuscular blockade may lead to about 35% of patients with residual weakness. It is not time to get rid of these devices completely. Going forward, the role of the peripheral nerve stimulator may be for neuromuscular monitoring when quantitative monitors are not available or to provide additional qualitative information during the transition to the newer quantitative monitors.

With that, we are going to make the transition to talking about quantitative monitors now which may be classified depending on the monitoring modality or the type of the device, hand-held which could be used outside of the operating room including the recovery room and intensive care unit, standalone, or integrated into the anesthesia work station to facilitate recording in the electronic medical record.

The first quantitative monitor is Mechanomyography which is the historic gold standard. It is rather challenging to set up with required calibration. The objective measurements are determined by measuring the isometric contraction force following neurostimulation. This is an important monitor since newer quantitative monitors may be compared to this one.

Next up is acceleromyography and the name give it away since it uses Newton’s second law of motion, Force = Mass x Acceleration. This device has been studied and used extensively. It determines the objective measurements of neuromuscular function by measuring the response to neurostimulation using a transducer attached to the muscle. Have you used this device with the standard ECG electrodes placed over the ulnar nerve with the acceleration of the adductor pollicis muscle measured on a transducer placed on the thumb after neurostimulation? Alternative sites for the acceleromyography monitor include on the foot for the flexor hallucis brevis and on the face at the orbicularis oculi and corrugator supercilia. Anytime a new device is used, it is important to understand how it works as well. Have you heard of the “reverse fade” phenomenon, which is when a baseline, unparalyzed train of four is greater than 1.0. The baseline train of four ratio is used for normalization which is calculated as the current train of four ratio divided by the baseline train of four ratio. Adequate recovery from neuromuscular blockage occurs when the normalized train of four ratio is greater than 0.9. Normalization helps to decrease bias when compared to the mechanomyography and the baseline measurement can be done accurately with a preload device to stabilize the thumb followed by calibration prior to administering neuromuscular blocking agents. This step takes some time and is important during research studies, but may not be necessary during clinical patient care, but it can be helpful to prevent overestimating return to intact neuromuscular function. Another consideration with this device is the thumb motion. Restricted movement of the thumb, which may occur when the arms are tucked during the surgical procedure may lead to inaccurate and unreliable measurements of neuromuscular function. Finally, when patients are emerging from anesthesia, movement at the monitoring site may lead to artifact and unreliable measurements. Acceleromyography has come a long way with newer three dimensional transducers with improved quantification of the thumb motion, preload devices incorporated into the device for improved precision, and wireless devices with Bluetooth technology so that the measurements can be incorporated into the anesthesia workstation and patient record. These devices may be either handheld units or modules that are part of the anesthesia workstation.

I hope that you will go check out the article for a picture of this device and then you can take a sneak peak at the rest of the devices that we will be talking about next week during the exciting conclusion to our discussion of Advancements in Quantitative Neuromuscular Monitoring. Plus, we will hear from the author, Ross Renew again.

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.

We hope you are ready for all new APSF Newsletter articles in the February 2022 APSF Newsletter. We are so excited to discuss the new articles and feature more authors and perioperative anesthesia patient safety specialists. Plus, you could be an APSF Newsletter author too. The APSF Newsletter is the official journal of the Anesthesia Patient Safety Foundation with an audience that includes anesthesia professionals, perioperative providers, key industry representatives, and risk managers. The next deadlines is right around the corner so mark your calendars for March 15^th for the June issue. Some of the types of articles include case reports, Question and Answer, Letter to the Editor, Rapid Response as well as invited conference reports, editorials, and reviews all with a focus on anesthesia related perioperative patient safety issues. For more information, head over to APSF.org and click on the Newsletter heading. The last one down is guide for authors and I will include a link in the show notes as well. Plus, make sure that you click on the Subscribe via email heading as well and sign up to be on the APSF Newsletter email list so that you can get expedited access by email to our current APSF Newsletter issue.

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

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