History
In a study of 33 cases of AFE in Australia and New Zealand, the most common initial symptoms were a feeling of agitation or of impending doom (27%), hypotension (21%), dyspnea (15%) and evidence of fetal compromise (15%). Coagulopathy was the initial symptom in only 3% of patients but 73% ultimately developed a coagulopathy and 85% required transfusion of blood products. Six percent of patients presented with either cardiac arrest or an arrhythmia. [23]
The classic history is that a woman in the late stages of labor becomes acutely dyspneic with hypotension. There may be a preceding period of agitation or a sense of impending doom. Altered mentation may or may not be present. She may experience seizures quickly followed by cardiac arrest. If undelivered, the fetus will demonstrate loss of heart rate variability followed by decelerations and ultimately a terminal bradycardia. Massive DIC-associated hemorrhage follows and then death. Most patients die within an hour of onset.
Data from the United Kingdom Obstetric Surveillance System (UKOSS) from 2005-2011 showed that 53% of women given a diagnosis of AFE presented at or before delivery. The remaining patients presented an average of 19 minutes after delivery. [17]
In the United States AFE registry 70% of patients presented during labor, 19% presented during cesarean delivery and 11% presented after delivery.
There are case reports of AFE occurring during abortion, after abdominal trauma, amniocentesis and during amnioinfusion.
A uniform diagnostic criteria for amniotic fluid embolism has been suggested in order to ensure that researchers use the same definition when reporting events. All of the following must be present for a diagnosis of AFE [5] :
1. Sudden onset of cardiorespiratory arrest or both hypotension (systolic BP < 90mm HG) and respiratory compromise (dyspnea, oxygen saturation < 90%)
2. Documentation of overt DIC following the events in item 1. Coagulopathy must be detected prior to the loss of enough blood to itself be the cause of a dilutional or consumptive coagulopathy.
DIC during pregnancy is assessed using the scoring system of the International Society of Thrombosis and Hemostasis. A score ≥ 3 is consistent with overt DIC in pregnancy.
Scoring system for DIC during pregnancy (Open Table in a new window)
| SCORE | 0 | 1 | 2 |
|---|---|---|---|
| Platelets | >100,000/mL | < 100,000/mL | < 50,000/mL |
| Prothrombin time or INR | < 25% increase | 25-50% increase | >50% increase |
| Fibrinogen | >200 mg/L | < 200 mg/L |
3. Clinical onset during labor or within 30 minutes of the delivery of the placenta
4. No fever (≥38.0 C) during labor
The authors stress that the above criteria are for research only and that in clinical practice patients may have atypical AFE in which all the required elements are not met. The Amniotic Fluid Embolism foundation is interested in plasma and serum obtained during the admission from patients experiencing AFE. Instructions for samples and records can be found on the Amniotic Fluid Embolism Foundation website.
The United Kingdom Obstetric Surveillance System (UKOSS) and the Australasian Maternity Outcomes Surveillance System (AMOSS) defines AFE for the purpose of case reporting as [16, 24] :
EITHER a clinical diagnosis based on acute hypotension or cardiac arrest, acute hypoxia or coagulopathy in the absence of any other potential explanation for the symptoms and signs observed
OR a pathological/postmortem diagnosis based on the presence of fetal squames or hair in the lungs.
Physical
The classic triad of AFE is hypoxia, hypotension and coagulopathy. The following signs and symptoms are indicative of possible AFE:
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Hypotension: Blood pressure may drop significantly with loss of diastolic measurement.
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Dyspnea: Labored breathing and tachypnea may occur.
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Seizure: Tonic clonic seizures are seen in 50% of patients.
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Cough: This is usually a manifestation of dyspnea.
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Cyanosis: As hypoxia/hypoxemia progresses, circumoral and peripheral cyanosis and changes in mucous membranes may manifest.
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Fetal bradycardia: In response to the hypoxic insult, fetal heart rate may drop to less than 110 beats per minute (bpm). If this drop lasts for 10 minutes or more, it is a bradycardia. A rate of 60 bpm or less over 3-5 minutes may indicate a terminal bradycardia.
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Pulmonary edema: This is usually identified on chest radiograph.
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Cardiac arrest
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Uterine atony: Uterine atony usually results in excessive bleeding after delivery. Failure of the uterus to become firm with bimanual massage is diagnostic.
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Coagulopathy or severe hemorrhage in absence of other explanation (DIC occurs in 83% of patients.) [25]
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Altered mental status/confusion/agitation
Tables
| SCORE | 0 | 1 | 2 |
|---|---|---|---|
| Platelets | >100,000/mL | < 100,000/mL | < 50,000/mL |
| Prothrombin time or INR | < 25% increase | 25-50% increase | >50% increase |
| Fibrinogen | >200 mg/L | < 200 mg/L |
