Amniotic Fluid Embolism

First Things First (assess and treat for the following)

  • Amniotic fluid embolism (AFE) occurs when there is a breach in the barrier between maternal circulation and amniotic fluid. Fetal material has been documented in the pulmonary circulation of asymptomatic women.
  • The postulated mechanisms include:
    • Obstruction of pulmonary vasculature from fetal debris
    • Inflammatory mediators leading to vasoconstriction and bronchospasm rather than mechanical factors
  • It is likely due to a combination of these factors that leads to:
    • Development of acute pulmonary hypertension and cor pulmonale
    • Sudden decrease in blood flow to the left ventricle, leading to vascular collapse
    • Ventilation/perfusion mismatches, leading to hypoxemia and its attendant complications
    • Activation of the extrinsic coagulation pathway, leading to disseminated intravascular coagulation (DIC)

History & Physical (assess for the following)

  • Signs & symptoms
    • Hypoxemia
    • Hypotension
    • Coagulopathy
    • Altered mental status
    • Seizures
    • Fetal distress
    • Fever
    • Chills
    • Headache
    • Nausea
  • The diagnosis of AFE is suspected when women present with above-mentioned signs and symptoms during:
    • Labor
    • Delivery
    • Immediate postpartum period
    • Rarely in the late postpartum period
  • AFE has also been reported following:
    • Amniocentesis
    • Therapeutic abortion
    • Abdominal trauma in pregnant individual
    • Intrapartum amnioinfusion
  • Differential diagnosis
    • Venous thromboembolism
    • Air embolism
    • Myocardial infarction
    • Septic shock
    • Preeclampsia/eclampsia
    • Postpartum hemorrhage
    • Anaphylaxis
    • Anesthetic complication
    • Transfusion reactions

Diagnostic Tests

  • The diagnosis of AFE is essentially a diagnosis of exclusion.
  • There is no laboratory or bedside investigation that can confirm the diagnosis.
  • It is suspected when a woman who is pregnant or in the immediate postpartum period acutely presents with shock along with severe respiratory distress.
  • Although most patients present in this manner, there is a subset of patients in whom the initial presentation may be severe hemorrhage secondary to DIC.
  • Occasionally the presentation may be subtle, with restlessness, altered mental status and/or hypoxemia.
  • It is important to exclude other fulminant conditions like sepsis, myocardial infarction, anaphylaxis, and transfusion reactions.
  • Labs: More than a diagnostic aid, these tests are useful in guiding resuscitation.
    • Arterial blood gas to evaluate ventilation and hypoxemia
    • DIC profile: These patients may develop DIC, as evidenced by elevated PT, PTT, low fibrinogen level and elevated fibrin split products (FSP).
    • Complete blood count: In the presence of DIC, hemoglobin and hematocrit tend to drop. Patients often develop thrombocytopenia and they usually have reactive leukocytosis.
    • Serum chemistries
  • Experimental studies have suggested that certain lab tests may be helpful:
    • Serum tryptase and histamine markers of mast cell activation (high)
    • Sialyl Tn - Fetal antigen (high)
    • Complement C3 & C4 (low)
    • Zinc coproporphyrin (high)
    • Although touted to be specific for AFE, they have no established role in confirming the diagnosis of AFE and remain experimental tools.
  • Radiographic findings are not diagnostic. Most of these patients show diffuse infiltrates suggestive of pulmonary edema.
  • An electrocardiogram should be obtained to look for signs of ischemia.
  • Echocardiogram to evaluate pulmonary artery pressure, right ventricular and left ventricular function
  • Historically, it was believed that the amniotic fluid debris found by aspirating blood from the distal port of a pulmonary artery catheter was pathognomonic of AFE; however, recent studies have shown that fetal elements can be found in some asymptomatic pregnant women.

General Management Principles

  • Given the rapidity with which AFE presents, it is essential to be vigilant and respond quickly.
  • The cornerstone of therapy is supportive care.
  • Hypoxemia
    • Supplemental oxygen while monitoring oxygen saturation
    • If hypoxemia with hemodynamic instability is present, intubation and mechanical ventilation is indicated.
    • AFE patients with ARDS should be placed on low tidal volume and high PEEP while monitoring the plateau pressure as recommended by the ARDS network.
  • Hemodynamic instability
    • These patients need to be resuscitated with fluids and vasopressors.
    • Transthoracic or transesophageal echocardiogram may be useful in guiding fluid therapy.
    • If patients are noted to have left-sided failure with pulmonary edema, therapy should include a combination of dobutamine along with either phenylephrine or norepinephrine.
    • The goal is to maintain a mean arterial pressure >65 mmHg.
  • Cardiac arrest
    • Advanced Cardiac Life Support including medications should be instituted immediately.
    • During cardiopulmonary resuscitation before delivery the uterus should be displaced to the left to avoid compression of aorta & inferior vena cava.
    • The goal is to restore maternal hemodynamics and deliver the fetus as soon as possible.
  • DIC
    • Frequent monitoring of the coagulation profile, including complete blood count and fibrinogen levels
    • Blood transfusion for hemorrhage
    • Patients need to be transfused with fresh frozen plasma & cryoprecipitate to correct coagulation abnormalities.
    • Platelet transfusions for patients with thrombocytopenia who are actively bleeding
    • Given the increased risk of bleeding with a coexisting coagulopathy, uterine atony must be treated aggressively with standard medical and surgical methods, including uterotonic medications, uterine artery embolization or ligation and hysterectomy.
  • Fetus
    • ~2/3 of patients are in labor when they are diagnosed. In these instances immediate delivery of the fetus is mandated to prevent further hypoxic damage.

Specific Management

  • N/A

Ongoing Assessment

  • AFE patients should be continuously monitored in an intensive care unit.
  • Continuous fetal monitoring until delivery is mandatory.
  • All patients need central venous IV access as well as arterial lines.

Complications

  • Maternal outcome
    • Mortality 13-86%
    • 7-85% of the survivors have neurologic deficits.
  • Fetal outcome
    • Mortality 21-22%
    • 29-50% of the survivors have neurologic deficits.

Authors

  • Jijo John, MD, and Gary T. Kinasewitz, MD

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Last updated: April 16, 2010

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TY - ELEC T1 - Amniotic Fluid Embolism ID - 534006 Y1 - 2010/04/16/ PB - Pocket ICU Management UR - https://anesth.unboundmedicine.com/anesthesia/view/Pocket-ICU-Management/534006/all/Amniotic_Fluid_Embolism ER -