Episode #135 Pros for Providing Monitored Anesthesia Care for ERCP

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 continuing our Pro-Con Debate once again this week with Part 2. We hope you listened to Episode #134 last week because we are continuing the conversation today. Don’t worry, you don’t need to choose a side, MAC or general anesthesia, yet, but you do need to stay tuned.

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

We are returning to the October 2022 APSF Newsletter for our featured article today, “Pro-Con Debate: Monitored Anesthesia Care Versus General Endotracheal Anesthesia for Endoscopic Retrograde Cholangiopancreatography” by Luke Janik, Samantha Stamper, Jeffrey Vender, and Christopher Troianos. To follow along with us, head over to APSF.org and click on the Newsletter heading. First one down is the Current Issue, October 2022 and then scroll down until you get to our featured article today. I will include a link in the show notes as well. This article is a reprint from Anesthesia and Analgesia from June 2022 with permission from International Anesthesia Research Society.

We are so excited to return to this article. Last week, we heard from one of the authors on the Pro-side of the debate, Samantha Stamper and we discussed arguments in favor of MAC for ERCP as well as the advantages and disadvantages of MAC for ERCP. In addition, we talked about a novel, rescue airway technique, gastroscope-facilitated endotracheal intubation which may be used to secure the airway in a patient in the prone position who requires an urgent or emergent intubation during an ERCP procedure as part of the conversion from MAC to GA. Remember, there is a low conversion rate from MAC to GA at less than 4%.

Today, we are going to continue the conversation about MAC for ERCP and discuss clinical monitoring, options to provide supplemental oxygen, and a safe and effective anesthetic plan. Before we can talk about the anesthetic plan, we are going to review the risk factors for sedation-related adverse events. This is covered in Table 3 in the article. Here we go.

• Obstructive sleep apnea
• Body Mass Index >35
• Male Sex
• ASA Physical Status > III
• Emergent Procedure
• Mallampati IV or Difficult airway
• Severe gastroesophageal reflux disease
• Esophageal/gastric mass

Next up, let’s review clinical monitoring when providing MAC for ERCP. Remember, you will need to continue to follow the standards for basic anesthesia monitoring which involves continuous monitoring of the following:

• patient’s oxygenation
• ventilation
• circulation
• and temperature

Thus, the monitors will need to include noninvasive blood pressures, pulse oximetry, electrocardiography, and capnography. Whether you use nasal cannula or simple face mask to deliver supplemental oxygen, it is critical to monitor end-tidal CO2 in order to quickly recognize apnea or obstruction. End-tidal CO2 monitoring give the anesthesia professional time to intervene to ensure adequate ventilation before the patient becomes hypoxic. Impedance pneumography and acoustic respiration rate monitor are additional monitors that can detect apnea before any changes in pulse oximetry occur.

In order to keep patients safe during a MAC procedure, it is vital to prevent hypoxemia and any related adverse events such as cardiac arrhythmias, hypotension, and cardiac arrest. The authors provide some insight into how to maintain adequate oxygenation during the procedure. It starts with preoxygenation which may involve 3 minutes in duration or 4 vital capacity breaths which can help to ensure at least 4 minutes of “safety time” or the time before a patient begins to desaturate following inadequate ventilation. Obese patients are at increased risk for hypoxemia due to the associated decreased functional residual capacity or FRC leading to a decrease in the “safety time” window. Maintaining adequate oxygenation and ventilation for obese patients in the prone position may be challenging especially if there are significant pulmonary and systemic comorbidities. Adequate preoxygenation for obese patients is imperative. Keep in mind that preoxygenation for all patients prior to starting sedation helps to increase the margin of safety if there is any apnea, hypoventilation, or airway obstruction that occurs following the first propofol bolus. The combination of adequate preoxygenation and end-tidal CO2 monitoring helps to ensure that the anesthesia and endoscopy team has time to perform airway maneuvers, such as a jaw thrust, or insert the endoscope for stimulation before the patient develops hypoxemia.

What is the best way to provide supplemental oxygen during MAC for ERCP? There are several options which provide different levels of fractional inspired oxygen:

• Nasal cannula
• High-flow nasal cannula
• Procedural oxygen masks
• Specialized endoscopy masks

What equipment do you have in your endoscopy suite and what is your preference? And does your equipment also include capnography monitoring as well? Another important consideration is the placement of a bite block prior to sedation to help prevent the patient from biting the endoscope and these bite blocks may also have a built-in airway feature as well as a suction port to help manage airway secretions. The next step before starting sedation is to have the patient self-position for the procedure which adds two benefits over general anesthesia. First, it helps decrease the risk of compression or nerve injury that may go unrecognized in a patient under general anesthesia. Second, less staff are required to help transfer and position the patient after induction and intubation.

Next up, we are going to review medications that may be used during MAC for ERCP. Let’s start with premedication options. Administration of glycopyrrolate may be used to decrease secretions and help to ensure that the topical anesthetic are effective. Timing for administration is important. Glycopyrrolate may need to be given in the preoperative holding area to make sure that it is working before the procedure and this is especially true in a busy endoscopy center with fast turnovers. Topical pharyngeal anesthesia is another important consideration and can help to decrease stimulation from placement of the endoscope. This may be done with benzocaine or lidocaine sprays or viscous lidocaine which can be administered as a swish and swallow treatment. Keep in mind that there is a risk of methemoglobinemia associated with the use of benzocaine. Clinical signs of acquired methemoglobinemia may include cyanosis, decreased pulse oximetry values, and chocolate-brown blood on arterial blood gas sample with normal PaO2 levels with confirmation from elevated levels of methemoglobin from an arterial blood gas sample. Treatment includes administration of oxygen and intravenous methylene blue. Check out the 2007 study by Kane and colleagues that looked at benzocaine administration for transesophageal echocardiography and revealed clinical risk factors that included sepsis, anemia, and hospitalization. I will include a link in the show notes as well.

Now, back to the article and it is finally time to start the sedation. The goals for providing sedation and monitored anesthesia care are easy titration, rapid recovery, and minimal side effects while maintaining spontaneous ventilation throughout. The first medication that comes to mind is probably Propofol, right? Propofol is easy to titrate to provide a wide range of sedation from light sedation to deep sedation while maintaining spontaneous ventilation. Options for providing analgesia during the procedure include shorting-acting opioids such as Fentanyl, dexmedetomidine, and ketamine. Keep in mind that if urgent airway access is necessary, it is often possible to end the procedure quickly, remove the endoscope, and then manage the patient’s airway appropriately. When the scope is removed, this may cause laryngospasm which must be recognized and treated quickly.

The most stimulating part of the procedure is insertion of the gastroscope. Following this, procedural stimulation remains rather constant throughout the procedure. As a result, it is often possible to provide adequate sedation while maintaining spontaneous ventilation. For sedation with propofol, patients often return to their cognitive baseline within 30-45 minutes with a slower return of psychomotor speed and reaction time. Other benefits of MAC are not needing to administer neuromuscular blocking drugs, less postoperative nausea and vomiting when inhalational anesthetics and opioids are not given, and increased patient satisfaction.

Another important consideration for the MAC for ERCP side is that it avoids general endotracheal anesthesia and the associated risks. This is an important part of developing the anesthetic plan, weighing the risks and benefits. Intubation risks include the following:

• Damage to the lip, tongue, teeth, or eyes
• Bronchial rupture
• Inability to secure the airway and need for surgical intervention.

Don’t forget about the risks associated with succinylcholine administration, which is often used for intubation since it has a rapid onset and short duration of action without need for reversal. These risks include myalgias, myoglobinemia, myoglobinuria, and malignant hyperthermia. Plus, let’s not forget that there are risks associated with non-depolarizing muscle relaxants including residual neuromuscular blockade and postoperative pulmonary complications. If reversal of neuromuscular blockade is required and Sugammadex is not available, patients may experience anticholinergic side effects as well.

We are really on a roll with the risks associated with general anesthesia. Patients are at risk for hypotension during general endotracheal anesthesia which may lead to an increased risk for myocardial injury, renal injury, and death. After intubation, patients may need to be positioned prone or semi-prone for the procedure which requires several team members to help position and secure the patient on the fluoroscopy table. Don’t let your guard down during positioning since patients are at risk for endotracheal tube displacement or accidental extubation. Endoscopy suites are a type of NORA location that may have less support from colleagues and other team members to help manage a complication or an emergency or even for turnovers between cases leading to decreased efficiency. Let’s take a look at the 2016 study, “Impact of endotracheal intubation on interventional endoscopy unit efficiency metrics at a tertiary academic medical center.” The authors looked at the impact of general endotracheal anesthesia on efficiency at a large interventional endoscopy center. The study included over 1400 patients who underwent 1635 procedures over a 6-month period  with evaluation of the following:

• Anesthesia ready time
• Endoscopist ready time
• Procedure time
• Room exit time
• Time interval between successive procedures
• Nonprocedural time elapsed
• Total time elapsed in the endoscopy unit
• Number of cases per room per day.

The results showed significant increases in all the efficiency metrics for intubated patients compared to non-intubated patients, except for time interval between successive procedures. Further analysis revealed that patients undergoing ERCP were intubated more often than patients undergoing other procedures at a rate of about 41% compared to 12.4%.

We made it to the end of the Pro-side of this debate, but we are going to let the authors give their closing argument. I am going to read their conclusion now.

“In conclusion, MAC offers significant benefits over GEA in properly selected patients undergoing ERCP. These benefits include faster cognitive recovery, decreased side effects from the medications used to induce GEA, decreased risk of airway injury, decreased postoperative pulmonary complications, and reduced time spent at the hospital due to quicker induction and shorter time to discharge, thereby enhancing efficiency metrics for the unit, the providers, and the patients. With proper monitoring, supplemental oxygen, and sedation carefully titrated to maintain spontaneous ventilation, MAC during ERCP is a safe and often a superior alternative to GEA.”

Okay, now we have heard from the Pro-side so that means that you will have to tune in next week as we discuss the Con-side of the debate which includes arguments in favor of general endotracheal tube anesthesia for ERCP. Mark you calendars and be sure to tune in next week.

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.

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

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