What are the diagnostic criteria and management strategies for amniotic fluid embolism?

Diagnosis and Management of Amniotic Fluid Embolism

Amniotic fluid embolism (AFE) is a clinical diagnosis characterized by a triad of sudden hypoxia, hypotension, and coagulopathy occurring during labor, delivery, or immediately postpartum, with no specific laboratory test available to confirm or refute the diagnosis. 1

Diagnostic Criteria

AFE should be considered in any pregnant or immediately postpartum woman who experiences:

• Sudden cardiovascular collapse or cardiac arrest
• Severe respiratory difficulty or hypoxia
• Seizures
• Unexplained coagulopathy

The diagnosis is based on clinical presentation and exclusion of other likely causes 1. While most cases (70%) occur during labor, AFE can also present after vaginal delivery (11%), during cesarean delivery (19%), or rarely during the first or second trimesters, pregnancy termination, or amniocentesis 1.

Clinical Presentation

The classic presentation often begins with:

• Anxiety, mental status changes, agitation, or sensation of doom
• Rapid progression to cardiorespiratory collapse
• Development of coagulopathy/hemorrhage
• Electronic fetal monitoring showing decelerations, loss of variability, and terminal bradycardia in undelivered patients 1

Differential Diagnosis

Consider other causes of sudden cardiorespiratory collapse:

• Pulmonary embolism
• Myocardial infarction
• Air embolism
• Anesthetic complications
• Anaphylaxis
• Eclampsia
• Sepsis 2

Management Algorithm

1. Immediate Resuscitation

• Initiate high-quality cardiopulmonary resuscitation with standard basic and advanced cardiac life support protocols 1, 2:

  • Rapid chest compressions (100/minute)
  • Compression depth of at least 2 inches
  • Ensure adequate chest recoil between compressions
  • Minimize interruptions
  • Switch providers every 2 minutes to avoid fatigue

• For undelivered patients:

  • Tilt patient to left lateral position or manually displace uterus laterally to prevent aortocaval compression
  • Consider immediate delivery for pregnancies ≥23 weeks gestation if cardiac arrest occurs 1, 2

• Provide respiratory support:

  • Administer oxygen to maintain saturation >95%
  • Consider early intubation for respiratory distress
  • After successful resuscitation, wean inspired oxygen fraction to maintain pulse oximetry 94-98% to avoid hyperoxia-induced reperfusion injury 2

2. Hemodynamic Management

• Perform early echocardiography (transthoracic or transesophageal) to identify right ventricular failure 3

• For right ventricular failure (early phase):

  • Administer inotropes: dobutamine (2.5-5.0 μg/kg/min) or milrinone (0.25-0.75 μg/kg/min)
  • Consider pulmonary vasodilators: inhaled nitric oxide (5-40 ppm), inhaled prostacyclin (10-50 ng/kg/min), or intravenous prostacyclin (1-2 ng/kg/min)
  • Use vasopressors: norepinephrine (0.05-3.3 μg/kg/min) or vasopressin
  • Avoid excessive fluid administration as it may worsen right ventricular failure 1, 2

• For left ventricular failure (later phase):

  • Optimize cardiac preload
  • Consider noninvasive ventilation or intubation if not already performed
  • Target mean arterial pressure of 65 mmHg using fluids, vasopressors, and inotropes as needed 2

3. Coagulopathy Management

• Perform early assessment of clotting status 1
• Activate massive transfusion protocol immediately 1, 2
• Use hemostatic resuscitation with 1:1:1 ratio of packed red cells, fresh frozen plasma, and platelets 3
• Maintain platelet count above 50,000/mm³
• Administer cryoprecipitate as needed to maintain serum fibrinogen >150-200 mg/dL 2, 3
• When available, use bedside thromboelastography to guide transfusion therapy 2
• Consider antifibrinolytics (tranexamic acid or epsilon aminocaproic acid) if hyperfibrinolysis is identified 2
• Avoid recombinant Factor VIIa except as a last resort when hemorrhage cannot be controlled with standard measures 2, 4

4. Uterine Atony Management

• Aggressively treat uterine atony with uterotonics (oxytocin, ergot derivatives, prostaglandins)
• For refractory cases, consider:
  • Uterine tamponade with packing or intrauterine balloons
  • Bilateral uterine artery ligation
  • B-Lynch suture
  • Hysterectomy in extreme cases 2
• Thoroughly inspect cervix and vagina for lacerations in vaginal deliveries
• For diffuse bleeding during cesarean delivery not amenable to surgical control, consider packing the pelvis and transfer to ICU for delayed closure 2

5. Advanced Interventions

• Consider venoarterial extracorporeal membrane oxygenation (VA-ECMO) for:
  • Prolonged cardiopulmonary resuscitation
  • Severe ventricular dysfunction refractory to medical management
  • Note: Anticoagulation during ECMO may worsen bleeding in coagulopathic patients 2, 3, 5

6. Post-Resuscitation Care

• Maintain mean arterial pressure of 65 mmHg
• Aggressively treat fever to prevent worsening of ischemia-reperfusion brain injury
• Maintain serum glucose between 140-180 mg/dL with insulin infusions if needed
• Consider targeted temperature management (32-36°C) in patients without significant bleeding or coagulopathy, targeting 36°C rather than lower temperatures to minimize hemorrhage risk 2

Important Caveats

• Do not delay blood product administration while awaiting laboratory results 2
• Avoid making the diagnosis of AFE based solely on hemorrhage from persistent atony with secondary coagulopathy 2
• AFE is an immunologically mediated response to fetal or placental antigens entering maternal circulation, similar to anaphylactoid or systemic inflammatory response syndrome 4, 6
• Mortality remains high, with case fatality rates exceeding 50% in classic cases characterized by cardiovascular collapse and coagulopathy 2
• Surgical trauma may be a potential trigger for AFE in rare cases 7

Remember that early recognition and aggressive multidisciplinary management are essential to improve outcomes in this rare but potentially lethal obstetric emergency.