Amniotic Fluid Embolism

A month ago I wrote about the death of a co-workers wife. Recently I found out the cause of death was from an Amniotic fluid embolism. The following is taken from the eMedicine online medical database:

Background: Amniotic fluid embolism is a rare obstetric emergency in which amniotic fluid, fetal cells, hair, or other debris enter the maternal circulation, causing cardiorespiratory collapse.

In 1941, Steiner and Luschbaugh described amniotic fluid embolism for the first time after they found fetal debris in the pulmonary circulation of women who died during labor.

Current data from the National Amniotic Fluid Embolus Registry suggests that the process is more similar to anaphylaxis than to embolism, and the term anaphylactoid syndrome of pregnancy has been suggested.

The diagnosis has traditionally been made at autopsy when fetal squamous cells are found in the maternal pulmonary circulation; however, fetal squamous cells are commonly found in the circulation of laboring patients who do not develop the syndrome. In a patient who is critically ill, aspirate of the distal port of a pulmonary artery catheter that contains fetal squamous cells is considered suspicious for but not diagnostic of amniotic fluid embolism syndrome. Do not neglect other causes of hemodynamic instability.

Pathophysiology: The pathophysiology of amniotic fluid embolism is poorly understood. Amniotic fluid and fetal cells enter the maternal circulation, triggering a 2-phase process. In phase I, pulmonary artery vasospasm with pulmonary hypertension and elevated right ventricular pressure cause hypoxia. Hypoxia causes myocardial and pulmonary capillary damage, the left heart fails, and acute respiratory distress syndrome develops.

Women who survive the above events may enter phase II. This is a hemorrhagic phase characterized by massive hemorrhage with uterine atony and disseminated intravascular coagulation (DIC); however, fatal consumptive coagulopathy may be the initial presentation.

Frequency:

• In the US: Incidence of amniotic fluid embolism is estimated at 1 case per 8000-30,000 pregnancies.
• Internationally: Incidence is similar to that of the United States.

Mortality/Morbidity: Maternal mortality approaches 80%. Mortality was 61% in the national registry, which listed 46 cases. Five to 10% of maternal mortality in the United States is due to amniotic fluid embolism. Of patients with amniotic fluid embolism, 50% die within the first hour of onset of symptoms. Of survivors of the initial cardiorespiratory phase, 50% develop a coagulopathy.

Survival is rare. Most women who survive have permanent neurologic impairment. Neonatal survival is 70%. No evidence indicates that survivors are at risk for amniotic fluid embolism during future pregnancies.

Race: No racial or ethnic predilection exists.

Sex: Amniotic fluid embolism only occurs in women.

Age: Previously, advanced maternal age was believed to be a risk factor. No relationship to age has been found in the National Amniotic Fluid Embolus Registry.

History: Amniotic fluid embolism usually occurs during labor but has occurred during abortion, abdominal trauma, and amnioinfusion.

A woman in the late stages of labor becomes acutely dyspneic with hypotension; she may experience seizures quickly followed by cardiac arrest. Massive DIC-associated hemorrhage follows and then death. Most patients die within an hour of onset.

Physical: In case reports, patients are described as developing acute shortness of breath, sometimes with a cough, followed by severe hypotension. The following signs and symptoms are indicative of possible amniotic fluid embolism:

• Hypotension: Blood pressure may drop significantly with loss of diastolic measurement.
• Dyspnea: Labored breathing and tachypnea may occur.
• Seizure: The patient may experience tonic-clonic seizures.
• Cough: This is usually a manifestation of dyspnea.
• Cyanosis: As hypoxia/hypoxemia progresses, circumoral and peripheral cyanosis and changes in mucous membranes may manifest.
• Fetal bradycardia: In response to the hypoxic insult, fetal heart rate may drop to less than 110 beats per minute (bpm). If this drop lasts for 10 minutes or more, it is a bradycardia. A rate of 60 bpm or less over 3-5 minutes may indicate a terminal bradycardia.
• Pulmonary edema: This is usually identified on chest film.
• Cardiac arrest
• Uterine atony: Uterine atony usually results in excessive bleeding after delivery. Failure of the uterus to become firm with bimanual massage is diagnostic.

Causes: Forty-one percent of patients in the national registry had a history of allergies, and amniotic fluid embolism was more likely with a male fetus. The condition is considered an unpredictable and unpreventable event, and the cause is unknown.