Amniotic fluid embolism
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: AFE
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Overview
Amniotic fluid embolism (AFE) is a rare and incompletely understood obstetric emergency in which amniotic fluid, fetal cells, hair or other debris enters the mother's blood stream via the placental bed of the uterus and triggers an allergic reaction. This reaction then results in cardiorespiratory (heart and lung) collapse and coagulopathy.
The condition is so rare (less than 1 in 20,000 deliveries) that most doctors will never encounter it in their professional careers, and as a result the exact process is poorly understood. However, it is believed that once the fluid and fetal cells enter the maternal pulmonary circulation a two-phase process occurs:
First phase: The patient experiences acute shortness of breath and hypertension. This rapidly progresses to cardiac arrest as the chambers of the heart fail to dilate and there is a reduction of oxygen to the heart and lungs. Not long after this stage the patient will lapse into a coma. 50% die within the first hour of symptoms.
Second phase: Although many women do not survive beyond the first stage, about 40 per cent of the initial survivors will pass onto the second phase. This is known as the hemorrhagic phase and may be accompanied by severe shivering, coughing, vomiting and the sensation of a bad taste in the mouth. This is also accompanied by excessive bleeding as the blood loses its ability to clot. Collapse of the cardiovascular system leads to fetal distress and death unless the child is delivered swiftly.
Historical Perspective
AFE is first described in 1926. [1][2]
Classification
There is no classification for AFE.
Pathophysiology
The exact pathophisiology of AFE is unknown. [3] Abnormal maternal response to fetal tissue exposure could be the initial step resulting AFE[4].
Causes
It is mostly agreed that this condition results from amniotic fluid entering the uterine veins and in order for this to occur there are three prerequisites:
- Ruptured membranes (a term used to define the rupture of the amniotic sac)
- Ruptured uterine or cervical veins
- A pressure gradient from uterus to vein
Although exposure to fetal tissue is common and thus finding fetal tissue within the maternal circulation is not significant, in a small percentage of women this exposure leads to a complex chain of events resulting in collapse and death.
- Drugs causing amniotic fluid embolism
- Dinoprostone.
Differentiating Amniotic fluid embolism from other Diseases
Epidemiology and Demographics
- The prevalence of [disease name] is approximately [number or range] per 100,000 individuals worldwide.
- In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].
Age
- Patients of all age groups may develop [disease name].
- [Disease name] is more commonly observed among patients aged [age range] years old.
- [Disease name] is more commonly observed among [elderly patients/young patients/children].
Gender
- [Disease name] affects men and women equally.
- [Gender 1] are more commonly affected with [disease name] than [gender 2].
- The [gender 1] to [Gender 2] ratio is approximately [number > 1] to 1.
Race
- There is no racial predilection for [disease name].
- [Disease name] usually affects individuals of the [race 1] race.
- [Race 2] individuals are less likely to develop [disease name].
Risk Factors
- Common risk factors in the development of [disease name] are [risk factor 1], [risk factor 2], [risk factor 3], and [risk factor 4].
Natural History, Complications and Prognosis
- The majority of patients with [disease name] remain asymptomatic for [duration/years].
- Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
- If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
- Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
- Prognosis is generally [excellent/good/poor], and the [1/5/10year mortality/survival rate] of patients with [disease name] is approximately [#%].
Diagnosis
Diagnostic Criteria
AFE is a diagnosis of exclusion. Classic triad of hypoxia, hypotension, and subsequent coagulopathy in mother especially after labor could be AFE. [5]
Symptoms
- [Disease name] is usually asymptomatic.
- Symptoms of [disease name] may include the following:
- [symptom 1]
- [symptom 2]
- [symptom 3]
- [symptom 4]
- [symptom 5]
- [symptom 6]
Physical Examination
- Patients with [disease name] usually appear [general appearance].
- Physical examination may be remarkable for:
- [finding 1]
- [finding 2]
- [finding 3]
- [finding 4]
- [finding 5]
- [finding 6]
Laboratory Findings
- There are no specific laboratory findings associated with [disease name].
- A [positive/negative] [test name] is diagnostic of [disease name].
- An [elevated/reduced] concentration of [serum/blood/urinary/CSF/other] [lab test] is diagnostic of [disease name].
- Other laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].
Imaging Findings
- There are no [imaging study] findings associated with [disease name].
- [Imaging study 1] is the imaging modality of choice for [disease name].
- On [imaging study 1], [disease name] is characterized by [finding 1], [finding 2], and [finding 3].
- [Imaging study 2] may demonstrate [finding 1], [finding 2], and [finding 3].
Other Diagnostic Studies
- [Disease name] may also be diagnosed using [diagnostic study name].
- Findings on [diagnostic study name] include [finding 1], [finding 2], and [finding 3].
Treatment
Medical Therapy
- There is no treatment for [disease name]; the mainstay of therapy is supportive care.
- The mainstay of therapy for [disease name] is [medical therapy 1] and [medical therapy 2].
- [Medical therapy 1] acts by [mechanism of action 1].
- Response to [medical therapy 1] can be monitored with [test/physical finding/imaging] every [frequency/duration].
Surgery
- Surgery is the mainstay of therapy for [disease name].
- [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
- [Surgical procedure] can only be performed for patients with [disease stage] [disease name].
Prevention
- There are no primary preventive measures available for [disease name].
- Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].
- Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].
References
- ↑ West M (January 2016). "Amniotic fluid embolism: a historical perspective in diagnosis and management". BJOG. 123 (1): 110. doi:10.1111/1471-0528.13528. PMID 26715344.
- ↑ Gei AF, Vadhera RB, Hankins GD (March 2003). "Embolism during pregnancy: thrombus, air, and amniotic fluid". Anesthesiol Clin North America. 21 (1): 165–82. PMID 12698839.
- ↑ Tamura N, Farhana M, Oda T, Itoh H, Kanayama N (April 2017). "Amniotic fluid embolism: Pathophysiology from the perspective of pathology". J. Obstet. Gynaecol. Res. 43 (4): 627–632. doi:10.1111/jog.13284. PMID 28188959.
- ↑ Shamshirsaz AA, Clark SL (December 2016). "Amniotic Fluid Embolism". Obstet. Gynecol. Clin. North Am. 43 (4): 779–790. doi:10.1016/j.ogc.2016.07.001. PMID 27816160.
- ↑ Sundin CS, Mazac LB (2017). "Amniotic Fluid Embolism". MCN Am J Matern Child Nurs. 42 (1): 29–35. doi:10.1097/NMC.0000000000000292. PMID 27755062.