Earlier in the summer, I wrote a blog discussing the challenges, intricacies, and educational pitfalls of postpartum hemorrhage in EMS. The blog's aftermath yielded much great discussion of amniotic fluid emboli and how we can best prepare to manage these patients prehospitally
I have always known that amniotic fluid embolism patients exist. I even know of cases that my colleagues have managed! But despite all of this, I was not incredibly well-versed on the topic. Let’s dive into it together, shall we?
Epidemiology
Amniotic fluid embolism (AFE) is an incredibly rare yet catastrophic pathology during which fetal debris and/or amniotic fluid enters the maternal central circulation in the third trimester of pregnancy or, most commonly, during the labor process. Due to the rarity of AFE, it is not precisely known how often it occurs; however, some literature indicates that 1:15,000-50,000 women experience an AFE during the intrapartum or postpartum stages of their pregnancy.
Despite the rarity of AFE, the aftermath is deadly, with maternal mortality rates >50%, most commonly affecting women with comorbidities such as high gestational age, pre-eclampsia, eclampsia, obesity, and underlying endocrine and cardiovascular disorders. On the other hand, neonatal mortality in AFE is much lower, approximately 20%. However, >50% of neonates who fall victim to maternal AFE exposure during childbirth suffer from long-term deficits associated with anoxic brain injury.
Pathophysiology
While a fetus is in utero, it resides within the amniotic sac, a protective barrier and binding point for the placental structures between the mother and fetus. During the normal labor process, the amniotic sac ruptures, allowing the amniotic fluid within to provide a natural lubricant for fetal expulsion. As the cervix begins to dilate secondary to uterine contraction, the fetus will utilize the amniotic fluid from the sac to assist it in traversing the vaginal canal.
This is normal labor, though. What happens when an AFE occurs, making it abnormal? To be honest, nothing much! Generally speaking, the labor process follows the same guiding physiologic principles even in the presence of an AFE, as far as the fetus is concerned. Where things get hairy is on the maternal side of things.
When an AFE occurs in a third-trimester pregnant female, the rupture of the amniotic sac kicks off the road to devastation. In these cases, usually secondary to placental trauma or abruption creating a pathway, amniotic fluid and fetal debris from inside the amniotic sac enter the central circulation of the mother, which begins circulating in her vasculature.
AFEs are rare, and little is known about the etiology of their development or the pathophysiology of their damage. However, the most widely subscribed-to understanding is a hybrid of distributive and obstructive shock. Because the mother has never had fetal debris and/or amniotic fluid in her circulation, she has no IgE available to fight the systemic reaction caused by this introduction. Because of this, she essentially develops a massive anaphylactoid reaction resulting in severe pulmonary vasoconstriction.
As the pulmonary artery becomes blocked, resulting in a lack of pulmonary flow, hypoxemia occurs, leading to a state of cor pulmonale and a total failure of the right ventricle. The presence of cor pulmonale ultimately leads to left ventricular failure because there is no flow through the left ventricle! As you might imagine, no flow through the left ventricle is bad… like really, really bad. This lack of flow and a bilaterally failing heart results in extreme hypotension and in many cases, cardiac arrest.
To make matters worse, it is thought that the systemic anaphylactoid reaction accompanied by cor pulmonale leads to a release of the Factor-VIIa enzymes in the clotting cascade. The release of Factor-VIIa enzymes leads to excessive platelet response and hyperutilization of platelets, exhausting the stores, leading to disseminated intravascular coagulation (DIC) and uncontrolled hemorrhage.
Clinical Presentation/Assessment
Let’s think about what this looks like, shall we? There are essentially two presentations that may occur:
The first is a female patient of childbearing age who is late in her third trimester of pregnancy and is either not yet in labor or amidst the labor process. Regardless, she complains of sudden and severe shortness of breath. When you evaluate her, you notice that she is rapidly becoming tachycardic and hypotensive and is profoundly tachypneic with oxygen saturations well below 90%. As a result of her hypoxia and accompanying hypoperfusion and hypoxemia, she rapidly deteriorates into cardiac arrest, at which time the labor process is halted, requiring your astute resuscitation.
The second is a female patient of childbearing age who has just delivered a baby and begins to hemorrhage uncontrollably, during which she becomes short of breath. When she is evaluated, your assessment findings resemble what you would find in option one, however this female already has a head start on her volume loss as she has already delivered.
Regardless, of whether you are caring for female one or two, we should be aware that both cases are immensely complicated to manage and require our most valiant efforts. But how do we manage them? Unfortunately, much like pathophysiology, there is not much guidance on how to most effectively resuscitate a patient suffering from an AFE. However, many lessons learned from the fields of trauma and perfusion give some good indicators of what we could, and should, be trying.
Clinical Care
Regardless of the patient’s condition, one of the most primary focuses of the resuscitation should be improving oxygenation. Ensuring that aggressive airway control is occurring to promote oxygenation is essential. Whether that be with oxygen therapy, non-invasive positive pressure, or intubation, keeping the patient oxygenated is a must.
What about hemorrhage or risk thereof? We know that overloading patients with obscene amounts of isotonic crystalloid is just not the answer. Resuscitating patients with low titer O whole blood or with component therapy in a ratio of 1:1:1, with packed red blood cells, platelets, and plasma, is impactful as it will help promote the restoration of circulation and add platelets and hemoglobin to the depleted store. However, much like in trauma, it is well known that component therapy in resuscitation is most effective when utilized with other mediums. In this case, medications like Tranexamic Acid, Pitocin, or Hemabate are thought to be beneficial.
It is important to note that the AFE patient is unique in that they are essentially experiencing an anaphylactoid reaction, resulting in distributive shock, a pulmonary embolism, resulting in obstructive shock, and volume loss, resulting in hemorrhagic shock, simultaneously. Controlling hemorrhage with fundal massages, blood products, tocolytics, and antifibrinolytics are widely known to be beneficial as we use them often in the care of patients with trauma and postpartum hemorrhage. Furthermore, we also know that managing the oxygenation requirements of a patient with cor pulmonale is critical, as we do it often.
What’s interesting is that we have minimal guidance on how to manage what is essentially an anaphylactoid reaction to what is, in part, oneself. In the standard care of anaphylactoid reactions, we administer Epinephrine, Diphenhydramine, steroids, and bronchodilators. Could this work for the AFE patient? The American Academy of Obstetrics and Gynecology isn’t sure. However, what they are sure about is that the administration of inotropic agents to a patient in need is good care, so don’t forget about the administration of norepinephrine to these patients to assist with cardiac output and perfusion of our efforts.
So far this seems like a slew of complicated resuscitation tactics. Is there anything else we can do? Indeed, there is! Have you heard of the “A-OK” method?” That’s okay, I hadn’t either.
The A-OK method is one of the only resuscitative acronyms for AFE patients, and is designed to remind clinicians of some off label pharmacologic interventions that may be effective in a last ditch effort.
A- Atropine 1mg: Atropine may serve to reverse parasympathetic activity that contributes to vasospasm.
O- Ondansetron 8mg: Ondansetron blocks receptors that may be found in the heart and lungs which contribute to pulmonary vasoconstriction and subsequent cor pulmonale.
K- Ketorolac 30mg: Ketorolac blocks thromboxane, which is a platelet activator. This blockade is thought to assist with the slowing of hemorrhage by reducing platelet response.
After investigating this resuscitation care, I must say that it makes much more sense. However, despite that, my mind kept going back to the female patient who suffered an intrapartum cardiac arrest. These cases are incredibly sad and rarely yield survivable outcomes, for the mother or fetus. Definitive care for an intrapartum cardiac arrest is a maternal perimortem cesarian section, which may be performed by any emergency physician.
Should you find yourself caring for a patient with an AFE, or otherwise, suffering from an intrapartum cardiac arrest, it is important that you recognize that this is not your standard cardiac arrest patient, but rather a unique circumstance requiring your astute, stepwise care.
First and foremost, I think it’s important to confess that I HATE the expression “load and go,” as I believe it most often results in bad care. In the resuscitation of a routine cardiac arrest patient who is being transported, we often resuscitate these patients for an extensive period before doing so, as we know it is most effective for the patient. We can all agree upon this.
Intrapartum cardiac arrests, however, are a totally different ball game and require a much different mental model. Sure, we still do CPR, defibrillate as needed, and give Epinephrine based upon our local guidance. But there are a few nuances to this resuscitation that we must be cognizant of if we want to promote the highest likelihood of maternofetal survivability.
The first of which, is fundal displacement. Pregnant females have large fundal abdomens, which place increased pressure on the inferior vena cave (IVC), thus reducing perfusion. When performing CPR on a pregnant female, a clinician on the resuscitation team will need to be dedicated to displacing the fundal abdomen towards the left shoulder. This reduces the load from the IVC and promotes perfusion. Moreover, when a pregnant female enters a state of shock, specifically one that is volume driven, she begins to shunt blood away from the uterus, and fetus therein, back to her core in an attempt to improve her own perfusion. Displacing the fundal abdomen allows for blood flow back through the placenta, to the fetus.
In addition to fundal displacement, it is important to remember that pregnant females have an increase in blood volume of 25-40%, depending on their underlying health. As a result, the pregnant female is going to require more aggressive oxygenation and airway care as well as be more prone to electrolyte abnormalities and subsequent dysrhythmias. If you find yourself caring for a patient in refractory ventricular fibrillation or tachycardia, consider administering Magnesium Sulfate, as the patient's cardiac arrest may be secondary to an eclamptic state.
Finally, and most simplistically, but certainly not least important, move-it! As we discussed, in most cases we would “stay and play,” as the old vernacular suggestions, in the cardiac arrest patient. For patients suffering from intrapartum cardiac arrest, I would encourage you to transport the patient as expeditiously, but safely, as possible to the closest emergency department. Like I said, any emergency physician, as much as they may not love it, can perform a perimortem cesarian section. Oppositely, if the patient is not suffering from cardiac arrest, I would still encourage you to move with haste but try to transport the patient to a hospital with an in-house obstetrician and operating room capabilities, while notifying the hospital as early as possible.
Oh, and one more thing… although as I sit and write this blog I have never cared for a patient suffering from AFE, I have cared for a patient who was late in her third trimester who suffered an intrapartum cardiac arrest secondary to domestic violence… and it was the worst call of my career. Don’t forget about the self-care component of these cases for you and your colleagues. They are no joke.
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Clark, S. L., Hankins, G. D., Dudley, D. A., Dildy, G. A., & Porter, T. F. (1995). Amniotic fluid embolism: Analysis of the national registry. American Journal of Obstetrics and Gynecology, 172(4), 1158-1169. DOI: 10.1016/0002-9378(95)91453-0
Knight, M., Tuffnell, D., Brocklehurst, P., Spark, P., & Kurinczuk, J. J. (2010). Incidence and risk factors for amniotic-fluid embolism. Obstetrics & Gynecology, 115(5), 910-917. DOI: 10.1097/AOG.0b013e3181da1814
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