Epidemiology

Epidemiologic Features

• Timing: amniotic fluid embolism occurs anywhere between 20 wks of pregnancy and 48 hrs postpartum (but most cases occur during labor)
  • Amniotic Fluid Embolism Post-Delivery: most cases occur within 1 hr after delivery (although may occur up to 48 hrs post-partum)
• Incidence: amniotic fluid embolism occurs 1 in 8,000-80,000 births
• Mortality: amniotic fluid embolism accounts for 10-15% of all maternal deaths (it is the 3rd leading cause of maternal mortality)
• Type of Delivery: amniotic fluid embolism can occur in both spontaneous and C-section deliveries, as well as with therapeutic abortions

Risk Factors

• Abruptio Placentae (see Abruptio Placentae)
  • Epidemiology: present in 50% of cases
• Advanced Maternal Age
• Amniocentesis
  • Epidemiology: xxx
• Fetal Distress/Death
• Meconium Staining
• Multiparity
• Prior Fetal Demise
  • Epidemiology: present in 40% of cases
• Therapeutic Abortion
  • Epidemiology: amniotic fluid embolism occurs in 1:400,000 abortions
• Tumultuous Labor
• Use of Intrauterine Pressure Catheters
• Use of Uterine Stimulants

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Physiology

• Amniotic Fluid Entry into Maternal Bloodstream through Uterine Venous Channels: possible occurs when membranes rupture or uterus is instrumented
  • May Involve Thromboplastic Activity of Amniotic Fluid with Intravascular Activation and Coagulation
    • Development of Hyperfibrinolytic State (see Hyperfibrinolytic States)
  • Pulmonary Vascular Obstruction from Amniotic Fluid Embolism: may result in pulmonary hypertension
    • Autopsy Findings: mucin, fetal squamous cells, lanugo, vernix caseosa, bile-containing meconium within the pulmonary vasculature
  • Alveolar Capillary Leak
  • Anaphylaxis to Fetal Antigens
  • Left Ventricular Dysfunction with Pulmonary Edema

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Diagnosis

Complete Blood Count (CBC) (see Complete Blood Count)

• Thrombocytopenia (see Thrombocytopenia)
  • Epidemiology: may occur

Chest X-Ray (CXR) (see Chest X-Ray)

• Findings
  • Normal
  • Pulmonary Edema: may be seen in some cases

Chest CT (see Chest Computed Tomography)

• Findings
  • Normal
  • Pulmonary Edema: may be seen in some cases

Chest CT Pulmonary Artery Angiogram (CTPA) (see Computed Tomography Pulmonary Artery Angiogram)

• Negative for Acute Pulmonary Embolism

Ventilation-Perfusion (V/Q) Scan (see Ventilation-Perfusion Scan)

• Normal: rules out acute pulmonary embolism

Pulmonary Artery Angiogram (see Pulmonary Artery Angiogram)

• Usually Not Required

Echocardiogram (see Echocardiogram)

• Cardiac Output: usually normal
• Pulmonary Hypertension: may occur, but major hemodynamic impairment is related left ventricular dysfunction

Swan-Ganz Catheter (see Swan-Ganz Catheter)

• Examination of Pulmonary Arterial Blood: can be sent to look for squames, hair, and mucin (but detection of fetal squames is common even in normal post-partum females)

Pulmonary Function Tests (PFT’s) (see Pulmonary Function Tests)

• Decreased DLCO

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Clinical Manifestations

General Comments

• Symptom Onset: abrupt

Cardiovascular Manifestations

• Cardiac Arrest (see Cardiac Arrest)
• Hypotension/Shock (see Hypotension)
• Left Ventricular Failure (see Congestive Heart Failure)

Gastrointestinal Manifestations

• Nausea (see Nausea and Vomiting)

Hematologic Manifestations

• Disseminated Intravascular Coagulation (DIC) (see Disseminated Intravascular Coagulation)
  • Epidemiology: occurs in 40% of cases
  • Diagnosis
    • Platelet Count: decreased
    • Serum Fibrinogen: decreased
    • Fibrin Degradation Products: increased
    • D-Dimer: increased
    • Anti-Thrombin: decreased
    • Schistocytes: present
    • Plasma Clotting Times (INR and PTT) (see Prothrombin Time and Partial Thromboplastin Time): prolonged
    • Euglobulin Lysis Time: shortened
    • ADAMTS13 Activity (see ADAMTS13 Activity): usually normal
• Thrombocytopenia (see Thrombocytopenia)
  • Epidemiology: may occur

Neurologic Manifestations

• Altered Mental Status
  • Agitation (see Agitation)
  • Delirium (see Delirium)
• Tonic-Clonic Seizures (see Seizures)
  • Epidemiology: occur in 10-20% of cases

Pulmonary Manifestations

• Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome)
  • Epidemiology: occurs in 75% of cases
  • Clinical: dyspnea
• Pulmonary Hypertension (see Pulmonary Hypertension)

Other Manifestations

• Chills
• Hemorrhage
  • Epidemiology: occurs in 50% of cases

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Treatment

Supportive Care

• Blood Products: as required
• Mechanical Ventilation (see Invasive Mechanical Ventilation-General)
• Intravenous Fluid Resuscitation: as required for hemodynamic support
• Vasopressors: as required for hemodynamic support

Other Treatments

• Anti-Fibrinolytic Agents (see Anti-Fibrinolytics): unclear role
  • Epsilon Aminocaproic Acid (Amicar) (see Epsilon Aminocaproic Acid)
• Cryoprecipitate (see Cryoprecipitate): unclear role

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Prognosis

• Mortality Rate: <75% of patients survive the first hour of event
  • Overall Mortality Rate: >85%
• Long-Term Outcome: many survivors have long-term neurologic disability

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References

• xxx