Episode #126 Amniotic Fluid Embolism: Are You Prepared?

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 headed to the maternity unit today to discuss a catastrophic complication related to obstetric anesthesia. Have you taken care of a patient who developed an amniotic fluid embolism? This is a rare event with an incidence of about 1-2 in 100,000 pregnancies, but anesthesia professionals need to be prepared and will need to act quickly to help keep patients who develop an amniotic fluid embolism safe.

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!”

Our featured article today is from the latest October 2022 APSF Newsletter by David Arnolds called, “Recognition and Management of Amniotic Fluid Embolism: A Critical Role for Anesthesia Professionals on Labor and Delivery.” To follow along with us, head over to APSF.org and click on the Newsletter heading. First one down is the current issue. Then scroll down until you get to our featured article today. I will include a link in the show notes as well. Before we get into the article today, we are going to hear from the author. Here he is to introduce himself now.

[Arnolds] “My name is David Arnolds, and I’m an anesthesiologist at the University of Michigan Hospital in Ann Arbor, Michigan.”

[Bechtel] To kick off the show today, I asked Arnolds why he wrote this article. Let’s take a listen to what he had to say.

[Arnolds] “I wrote this article for the APS F newsletter on recognition and management of amniotic fluid embolism because it’s a rare but potential potentially catastrophic event. It’s rare enough that many anesthesiologists will only see it one or two times in their career, if at all, but it’s critical to be able to recognize it and management appropriately if and when you do.

So I wrote the article to try and highlight key features and principles of management, and hopefully provide an opportunity to increase awareness and improve outcomes of this rare but potentially deadly condition.

[Bechtel] Thank you so much to Arnolds for contributing to the show today. We will hear more from him in the future and don’t worry we will make sure to highlight the keys to management for a patient with an amniotic fluid embolism on the show, so don’t turn the dial.

Anesthesia professionals who provide on labor and delivery units need to be prepared since even though this is a rare event, there is a significant risk to patient safety with a mortality or permanent neurologic injury rate of 30-40% following an amniotic fluid embolism.  Did you know that in the United States amniotic fluid embolism or AFE is the second leading cause of maternal death on the day of delivery? Anesthesia professionals can make a big difference when caring for these patients with early recognition of a possible AFE and appropriate goal-directed management. This is supported in the literature since patient survival is higher when an obstetrician or anesthesia professional are present when the AFE occurs. This topic is so important to review since it is a rare event with an unknown etiology that requires a clinical diagnosis and treatment is supportive care. You might want to get out your notebooks and pencils for this one. Also, we have talked about cognitive aids before on this show and this is a time where a specific cognitive aid for your institution may come in handy. Anesthesia professionals who suspect an AFE, can state, “I am concerned about a possible amniotic fluid embolism” and then work through the initial management steps on the cognitive aid. There is a Society for Maternal-Fetal Medicine Special Statement: Checklist for initial management of amniotic fluid embolism published in 2021. I will include the citation in the show notes as well. This checklist is a sample only and should be modified for use at a specific facilities taking into account the available resources. We are going to take a brief detour from the article to review the sample checklist now.

The first part is to manage circulatory collapse. The steps include the following:

• Manage airway, breathing, and circulation.
• Assign a time keeper to call out time in 1 minute intervals.
• If no pulse, start CPR. Don’t forget to manually displace uterus and use a backboard.
• Consider moving to OR, but only if this can be accomplished in 2 minutes or less.
• If no pulse at 4 minutes, start perimortem cesarean delivery. Splash prep only without waiting for antibiotics with the goal to improve chances of resuscitation.

The second part is to manage uterine atony, DIC, and hemorrhage which includes the following steps:

• Start with oxytocin prophylaxis and additional uterotonics if needed
• Consider IO line for large bore IV access
• Start massive transfusion protocol with cryoprecipitate administration preferred to FFP to reduce the risk for volume overload.
• Use thromboelastometry if available.
• Administer tranexamic acid 1g IV over 10 minutes in the setting of DIC or hemorrhage.

The next part involves management of pulmonary hypertension and right ventricular failure with the following initial management steps.

• Consider performing an echo – TTE or TEE.
• Do not fluid overload. Volume administration in 500ml bolus and reassess.
• Consider norepinephrine for a vasopressor if needed.
• Consider inotropic support with dobutamine or milrinone.
• Consider pulmonary vasodilator if needed with inhaled nitric oxide, inhaled epoprostanol, IV epoprostanol, or oral sildenafil if awake and alert.
• Consider ECMO.
• Wean FiO2 with a goal O2 saturation between 94-98%.

The final part is a debrief after the event with the entire team to discuss opportunities for improvement in care or changes in the checklist, discuss family and staff support needs, and report the case to the Amniotic Fluid Embolism Registry.

Now, that we have reviewed this checklist, it’s time to get back to our featured article. There are no laboratory results or histology findings that are specific for AFE. Instead, this is a clinical diagnosis that involves cardiopulmonary collapse and coagulopathy in the absence of other conditions. As a result of the diagnostic uncertainty, studying AFE, determining the actual incidence, and evaluating treatment is difficult. There is a real risk for under-diagnosis of mild cases and over-diagnosis or inappropriate diagnosis of AFE in women who have cardiopulmonary collapse and coagulopathy from another etiology. There may be medical-legal pressure to diagnose AFE in certain cases of maternal mortality since it is the least preventable cause of maternal mortality as well. Another consideration is the different international criteria to diagnose AFE. Some of the diagnostic criteria include the presence of fetal epithelial cells in post-mortem histopathological samples from maternal lungs. However, there is evidence that fetal epithelial cells found in the maternal pulmonary circulation is not a sensitive or specific finding for AFE.

The Society for Maternal-Fetal Medicine and the Amniotic Fluid Embolism Foundation have developed diagnostic criteria for amniotic fluid embolism to help with research and reporting. These criteria are known as the Clark Criteria. You can find them in Table 1 in the article which I will include in the show notes. We will review the diagnostic criteria for research reporting of Amniotic Fluid Embolism now.

1. Sudden onset of cardiorespiratory arrest, or both hypotension with systolic blood pressure <90 mm Hg and respiratory compromise which may include dyspnea, cyanosis, or oxygen saturation, SpO2 < 90%.
2. Overt disseminated intravascular coagulation or DIC following appearance of these initial signs or symptoms. Coagulopathy must be detected prior to loss of sufficient blood to itself account for dilutional or shock-related consumptive coagulopathy.
3. Clinical onset during labor or within 30 min. of delivery of placenta
4. No fever (>38° C) during labor

To make the diagnosis of overt DIC in pregnancy, you need a score of greater than 3 by adding up the following points determined by laboratory results for platelet count, Prothrombin time or INR and Fibrinogen level. For platelet count, greater than 100,000 is 0 points, 1 point for less than 100,000 and 2 points for platelet count less than 50,000. When looking at a prolonged prothrombin time or INR, you will need to determine a change from baseline and less than 25% increase is 0 points, 25-50% increase is 1 point and if there is a greater than 50% increase that is 2 points. For a fibrinogen level greater than 200mg/dL is 0 points and less than 200 mg/dL is 1 point.

In obstetric patients, it is challenging to diagnose AFE, but it is important to differentiate from other etiologies of cardiovascular collapse in order to provide appropriate treatment and continue to work to keep patients safe. Let’s take a closer look at the study by Stafford and colleagues published in 2020, “Amniotic fluid embolism syndrome: analysis of the United States International Registry.” The authors reported on patients who were reported to have an AFE, but found to have a different actual diagnosis. The most common actual diagnosis was hypovolemic shock from postpartum hemorrhage. Anesthetic complications and sepsis related cardiovascular collapse were also on the list. Let’s review some strategies to be able to differentiate AFE from other causes of cardiovascular collapse in obstetric patients.

For cases that were misdiagnosed as AFE, obstetric hemorrhage was the most common actual diagnosis. This may happen because both AFE and severe hemorrhage can present with significant hypotension or cardiovascular collapse and coagulation abnormalities, but the antecedent event and the presence or absence of respiratory symptoms can help to make the correct diagnosis. AFE and sepsis may present similarly with hypotension, hypoxia, and coagulopathy, but there the time course for sepsis is usually longer and involves maternal hyper or hypothermia. Anaphylaxis is also on the differential and may present with hypotension and hypoxia, but coagulopathy is not seen with anaphylaxis and it occurs following exposure to an allergen such as medication, latex, or chlorhexidine skin prep. Anesthetic complications including a high spinal block may present with hypotension and respiratory compromise, but this complication does not involve coagulopathy and occurs following neuraxial anesthesia.

Other possible causes for hypotension and hypoxia in obstetric patients include pulmonary venous or air embolism or a primary cardiac cause such as an acute myocardial infarction. However, these etiologies are not associated with coagulopathy and are more likely to be seen in patients with risk factors or preexisting cardiac disease.

We have so much more to talk about when it comes to amniotic fluid embolism and keeping obstetric patients safe. We are going to continue our discussion about making the correct diagnosis and then move on to talk about management strategies. Plus, we will hear from Arnolds again. You only have one short week to wait.

In the meantime, we hope that you will consider applying for the joint APSF-FAER Mentored Research Training Grant. The Letter of Intent submissions for the 2023 grant open tomorrow, December 1^st 2022 and close on January 1, 2023. This is a two-year, $300,000 award to help anesthesiologists develop skills and preliminary data in order to become independent investigators in the field of anesthesia patient safety. The first step is the letter of intent prior to submitting a full application. So, what are you waiting for? Get your letter of intent in! I will include a link to the submission page in the show notes as well.

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. Plus, you can find us on twitter and Instagram!  See the show notes for more details and we can’t wait for you to tag us in a patient safety related tweet or like our next post on Instagram!! Follow along with us for anesthesia patient safety pictures and stories!!

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

© 2022, The Anesthesia Patient Safety Foundation