Learning objectives

• Signs of amniotic fluid embolism (AFE) 
• Management of AFE

Definition and mechanisms

• Amniotic fluid embolism (AFE) is one of the most catastrophic and life-threatening complications of pregnancy
• Occurs when amniotic fluid, fetal cells, hair, or other debris enters the maternal pulmonary circulation and causes cardiovascular collapse
• It is not a consequence of the “simple” mechanical respiratory obstruction, but a humoral effect causing anaphylactoid reactions or complement activation 
• It can occur in: 
  • Healthy women during labor 
  • During cesarean section
  • After abnormal vaginal delivery 
  • During the second trimester of pregnancy
  • 48 hours post delivery 
  • During abortion 
  • After abdominal trauma
  • During amnio-infusion 
• Any breach of the barrier between maternal blood and amniotic fluid forces the entry of amniotic fluid into the systemic circulation and results in a physical obstruction of the pulmonary circulation 
• The maternal prognosis after amniotic fluid embolism is very poor 

Signs and symptoms 

• Premonitory symptoms 
  • Acute dyspnea 
  • Sudden agitations 
  • Sudden chills, shivering, sweating 
  • Cough 
  • Anxiety 
  • Labored breathing 
  • Tachypnea 
• Altered mental status, seizures, and coma
• A rapid decline in pulse oximetry values or sudden absence or decrease in end-tidal carbon dioxide 
• Hypotension 
• Cyanosis: ventilation-perfusion mismatching as a result of pulmonary vascular constriction 
• Fetal bradycardia 
• Encephalopathy 
• Uterine atony
• Acute pulmonary hypertension
• Coagulopathy/ severe hemorrhage 

Diagnosis

• Four criteria must be present to make the diagnosis of AFE: 
  • Acute hypotension or cardiac arrest 
  • Acute hypoxia 
  • Coagulopathy or severe hemorrhage in the absence of other explanations 
  • All of these occur during labor, cesarean delivery, dilatation, and evacuation, or within 30 min postpartum with no other explanation of findings

Course of AFE

• Typical (classic) with three phases
  • Phase 1 respiratory and circulatory disorders 
  • Phase 2 coagulation disturbances of maternal hemostasis 
  • Phase 3 acute renal failure and acute respiratory distress syndrome (ARDS) 
  • Cardiopulmonary collapse 
• Atypical
  • Life-threatening hemorrhage due to disseminated intravascular coagulation (DIC)

Differential diagnosis

• Anaphylaxis 
• Aortic dissection 
• Cholesterol embolism 
• Myocardial infarction 
• Pulmonary embolism 
• Septic shock 
• Air embolism 
• Transfusion reaction
• Eclamptic convulsions and coma 
• Convulsion from the toxic reaction to local anesthetic drugs 
• Aspiration of gastric contents 
• Hemorrhagic shock in an obstetric patient 

Risk factors or causes 

• Unpredictable – unpreventable 

Risk factors: 

• Older maternal age 
• Multiparity 
• Intense contractions during labor 
• Abdominal trauma
• Cesarean section
• Induction of labor 
• Placenta previa 
• Eclampsia 
• Multiple pregnancies 
• Tears in the uterus or cervix 
• Early separation of the placenta from the uterus wall 
• Fetal factors: 
  • Fetal distress 
  • Fetal death 
  • Male baby 

Management

Suggested reading 

• Pollard BJ, Kitchen, G. Handbook of Clinical Anaesthesia. Fourth Edition. CRC Press. 2018. 978-1-4987-6289-2.
• Kaur K, Bhardwaj M, Kumar P, Singhal S, Singh T, Hooda S. Amniotic fluid embolism. J Anaesthesiol Clin Pharmacol. 2016;32(2):153-159.

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