amniotic fluid embolism

Epidemiology

• rare, 1 case per 8,000-30,000 pregnancies
• occurs in full-term pregnancy in a multiparous patients
• induction of labor doubles risk

Pathology

• tears in both fetal membranes & uterine veins
• circulatory collapse may occur when amniotic fluid reaches lungs
• respiratory distress & shock followed in 3- minutes to 4 hours by disseminated intravascular coagulation (DIC)
• intense fibrinolysis may accompany or follow the DIC

Clinical manifestations

• occurs during labor, during labor, cesarean delivery, dilation & evacuation, or within 30 minutes postpartum
• has also occurred during abortion, after abdominal trauma, & during amnioinfusion
• acute hypotension or cardiac arrest
• acute hypoxia, dyspnea
• coagulopathy or severe hemorrhage in the absence of other explanations
• seizure: tonic clonic seizures are seen in 50% of patients
• cough: generally a manifestation of dyspnea
• cyanosis: as hypoxia/hypoxemia progresses, circumoral & peripheral cyanosis & changes in mucous membranes may occur
• fetal bradycardia: in response to the hypoxic insult, fetal heart rate may drop to less than 110 beats per minute (bpm)
• pulmonary edema: generally identified on chest radiograph.
• cardiac arrest
• uterine atony: results in excessive bleeding after delivery
• may often be subclinical
• rarely, may be catastrophic

Laboratory

• arterial blood gas (ABG)
  • changes consistent with hypoxia/hypoxemia
  • decreased pH
  • decreased pO2
  • increased pCO2
  • base excess increased
• complete blood count (CBC) with platelets
  • hemoglobin & hematocrit levels generally normal
  • hrombocytopenia is rare
• prothrombin time & activated partial thromboplastin time
  • prothrombin time (PT) is prolonged because clotting factors are used up
  • activated partial thromboplastin time (aPTT) may be normal or shortened
• blood type & screen in anticipation of blood transfusion

Diagnostic procedures

• ECG may show tachycardia, ST segment & T-wave changes, & findings consistent with right ventricle strain.

Radiology

• chest radiograph posteroanterior & lateral, generally nonspecific, but evidence of pulmonary edema may be observed.

Management

• treatment is supportive
  • administer oxygen to maintain normal saturation
  • intubate if necessary
  • treat shock
  • consider pulmonary artery catheterization in patients who are hemodynamically unstable
  • continuously monitor the fetus
  • treat coagulopathy with FFP for a prolonged aPTT, cryoprecipitate for a fibrinogen level less than 100 mg/dL, & transfuse platelets for platelet counts less than 20,000/uL
• fibrinolytic inhibitors
  • epsilon-amino-caproic acid
  • tranexamic acid
• Surgery
  • emergent cesarean delivery in arrested mothers who are unresponsive to resuscitation
• follow-up
  • women who survive AFE will probably require ICU admission
  • left heart failure is a common late occurrence
  • survivors will probably have neurologic sequelae
    • consult neurologists as needed

More general terms

• pregnancy disorder; obstetric disorder; pregnancy complication
• embolism

Additional terms

• amniotic fluid
• pulmonary embolism (PE)