Amniotic fluid embolism

Amniotic fluid embolism is a special type of pulmonary embolism where the embolus is comprised of amniotic fluid. It can be a highly fatal complication of pregnancy, with an 80% maternal mortality rate.

Epidemiology

It is thought to complicate 1/8,000-80,000 pregnancies.

Clinical presentation

The classic clinical presentation is of abrupt dyspnea, cyanosis, and shock, shortly followed by a cardiorespiratory arrest and severe pulmonary edema. Some patients may present with an anaphylactic reaction caused by a hypersensitivity to the leukotrienes and arachnoid metabolites present in amniotic fluid. Central nervous system irritability producing convulsions is also considered a typical feature.

Pathology

It occurs when amniotic fluid is forced into the bloodstream through small tears in uterine veins during normal labor. However, in some cases, the placenta is disrupted by surgery or trauma.

Associations

• approximately 40% of patients may suffer a consumptive coagulopathy

Radiographic features

Plain radiograph

Non-specific but may have diffuse bilateral heterogeneous and homogeneous areas of increased opacity (can be indistinguishable from acute pulmonary edema due to other causes).

CT

Chest CT may show diffuse ground glass opacities (similar to early stage of acute respiratory distress syndrome) and prominent hilar pulmonary vasculature .  CT findings are also not specific and difficult to distinguish from other causes of acute noncardiogenic or cardiogenic pulmonary edema.

History and etymology

It was first reported by Ricardo Meyer in 1926 .