Amniotic fluid embolism (AFE)


Catastrophic complications of pregnancy in which amniotic fluid, fetal cells, hair, or other debris enters into the maternal pulmonary circulation, causing cardiovascular collapse.

History:

Amniotic fluid embolism was first reported by Ricardo Meyer in 1926. It was reported again in an experiment on laboratory animals by Warden in 1927. The importance of this condition and these early studies was not established until 1941, when Steiner and Lushbaugh reported the clinical and pathological findings of 42 women who died suddenly during or just after labor. The histopathology of the pulmonary vasculature of these women included mucin, amorphous eosinophilic material, and squamous cells. These findings formed the “classic” pathologic findings in AFE.


Aetiology

Risk factors:

United Kingdom Obstetric Surveillance System [UKOSS] report
  • Induction of labor
  • Caesarean section
  • Placenta previa and placental abruption (3-10x greater risk)
  • Eclampsia
  • Multiple pregnancies
  • Maternal age ≥35 years

Pathophysiology

Multifactorial pathogenesis:

  • Mechanical obstruction of vessels caused by AFE
  • Subsequent inflammatory effect by AFE on maternal circulatory system
  • Additional immunological mechanisms
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Pathophysiology of the amniotic fluid embolism (the arrows indicate the oxygen content of the blood: red – rich in oxygen, blue – poor in oxygen) | By derivative work: Hic et nuncLungs_diagram_detailed.svg: Patrick J. Lynch, medical illustratorHeart_circulation_diagram.svg: Patrick J. Lynch, medical illustratorVeincrosssection.svg:derivative work: Mouagip (talk)Veincrosssection.png: en:User:PdeferPlacenta.svg:Gray38.png: User Magnus Manske on en.wikipediaderivative work: Amada44  talk to meBrain_human_lateral_view.svg: Patrick J. Lynch, medical illustratorRed_drop.svg: Amada44 – Own work after Gei G., Hankins GDV.: Amniotic fluid embolism: an update. Contemp Ob/Gyn. January 2000;45:53–66 http://contemporaryobgyn.modernmedicine.com/obgyn/data/articlestandard/obgyn/512004/139541/g1a05304.jpgLungs_diagram_detailed.svgHeart_circulation_diagram.svgVeincrosssection.svgPlacenta.svgBrain_human_lateral_view.svgRed_drop.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=14533058

Clinical features

Amniotic fluid embolism typically occurs during labor and delivery or in the immediate postpartum period, after caesarean delivery, amniocentesis, removal of placenta, or with therapeutic abortion.

Classical triad:

All of these must occur during labor, cesarean delivery, dilation and evacuation, or within 30 min postpartum with no other explanation of findings.
  1. Hypoxia
  2. Hypotension
  3. Consumptive coagulopathy (including prolongation of coagulation times, hypofibrinogenemia and fibrinolytic activation, etc) and thrombocytopenia
Common signs and symptoms associated with amniotic fluid embolism | Thongrong, C., Kasemsiri, P., Hofmann, J. P., Bergese, S. D., Papadimos, T. J., Gracias, V. H., Adolph, M. D., & Stawicki, S. P. (2013). Amniotic fluid embolism. International journal of critical illness and injury science, 3(1), 51–57. https://doi.org/10.4103/2229-5151.109422

Diagnosis

AFE remains a diagnosis of exclusion, dependent on bedside evaluation and judgment.

American Society for Maternal-Fetal Medicine criteria:

  1. Sudden cardiopulmonary collapse, or hypotension (systolic blood pressure <90 mmHg) with hypoxia (SpO2<90%)
  2. DIC, according to ISTH definition
  3. Symptomatology either during labor or during placental delivery (or up to 30 minutes later)
  4. No fever

Differential diagnosis:

Differential diagnosis of amniotic fluid embolism | Thongrong, C., Kasemsiri, P., Hofmann, J. P., Bergese, S. D., Papadimos, T. J., Gracias, V. H., Adolph, M. D., & Stawicki, S. P. (2013). Amniotic fluid embolism. International journal of critical illness and injury science, 3(1), 51–57. https://doi.org/10.4103/2229-5151.109422

Management

The management of AFE is supportive and directed towards the maintenance of oxygenation, cardiac output and blood pressure, and correction of the coagulopathy. Treatment should take place in an intensive care unit, if possible.

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