AMNIOTIC FLUID EMBOLISM

 

Definition - a syndrome in which, following the infusion of a large amount of amniotic fluid into the maternal circulation, there is the sudden development of acute respiratory distress and shock

- 25% of women die within 1 hour of onset

 

The condition is rare -probable many cases are unrecognized, the diagnosis being erroneously attributed to obstetric shock, postpartum hemorrhage, or acute pulmonary edema.

 

Etiology / predisposing factors

1. Multiparity
2. Age > 30
3. Large fetus
4. Intrauterine fetal death'
5. Meconium in amniotic fluid
6. Strong uterine contractions
7. High incidence of operative delivery

 

Diagnosis (Definitive)

- the demonstration of the components of amniotic fluid in the maternal circulation

-histology of the lungs shows edema, alveolar hemorrhages , and emboli consisting of squamous cells, fat, mucin, bile, and lanugo hair

 

Clinical picture

1. Respiratory distress
2. Cyanosis
3. Cardiovascular collapse
4. DIC
5. Coma
6. Death
7. In non-fatal cases, lung scans using I(131) albumin may revela embolization

 

Differential diagnosis

1. Thrombotic pulmonary embolism
2. Air embolism
3. Fat embolism
4. Aspiration of gastric contents
5. Eclampsia
6. Stroke
7. Heart failure
8. Hemorrhagic shock
9. Ruptured uterus
10. Inverted uterus
11. Anesthetic drug reaction

 

 

Clinico-pathologic findings

 

Mode of infusion

 

-must be a tear in the fetal membranes and an opening into the maternal vasculature

-the two major sites of entry into the maternal blood stream are the endocervical veins and the
uteroplacental area

-rupture of the uterus increases the chance of AFE

-abruption of the placenta is a common occurrence

 

Cardio-respiratory consequences

 

-         exact mechanism is unknown

-         two theories

                                                               i.      overwhelming mechanical blockade of maternal pulmonary vessels by the emboli

                                                             ii.      anaphylactoid reaction to the particulate matter

-         three major aspects of the syndrome are probably due to a combination of the two

                                                               i.      sudden reduction in the amount of blood retuming to the left heart and decreased left ventricular output lead to peripheral vascular collapse

                                                             ii.      acute pulmonary hypertension and cor pulmonale and failure of the right heart produces peripheral edema

                                                            iii.      derangement of the ventilation - perfusion ratio leads to hypoxemia and tissue hypoxia, leading to cyanosis, restlessness, convulsions and death

 

Pathologic findings

Lungs

-                                 edema

-                                 alveolar hemorrhage

-                                 emboli of particulate material of amniotic fluid

-                                 dialted pulmonary vessels at the area of embolization

 

Heart

-                                 right side is often dilated

 

Coagulation system

 

-         release of thromboplastin into circulation leads to DIC, then hypofibrinogenemia and elevated fibrin degradation products

 

Uterus

- atony is common, mechanism not known

 

Management

 

-         in severe cases, no effective therapy

 

-         aims are reduction of pulmonary hypertension, increased tissue perfusion, relief of bronchospasm, control of hemorrhage, and general supportive measures

 

1. Oxygen
2. Bronchodilators and vasodilators
3. Correction of coagulation disorders (plasma, cryoprecipitate)
4. Blood transfusion
5. Inotropes
6. Manual exploration of uterus
7. Corticosteroids
8. Morphine
9. Invasive hemodynamic monitoring

 

Mortality

 

-         Maternal - about 75% of the deaths are a direct result of the effects of the embolism, and the rest are from hemorrhage

 

-         Fetal - mortality is high; 50% of the deaths occur in utero

 

 

 

 

 

MATERNAL MORTALITY

 

Definition -the number of maternal deaths per 100,000 live births

 

-the rates have decreased in North America, there are differences between different
socioeconomic groups, an estimate for the United States is 9.6/100,000

 

-advanced maternal age is a recognized risk factor due partly to the increase in hypertension and diabetes

 

CAUSES OF MATERNAL MORTALITY

 

1) Embolism 24%

 

2) Hypertensive disease 20%

 

3) Obstetric hemorrhage 26%

 

4) Sepsis 10%

 

5) Stroke 5%

 

6) Anesthesia-related 5%

 

7) Other 20%

 

 

 

PERINATAL MORTALITY

 

- This is the index used most commonly to assess the quality of reproductive care

 

Definition - the sum of intrauterine deaths plus deaths in the first seven days of life of infants weighing more than 500 g at birth, expressed per total 1000 live births

 

Etiology

 

Deaths prior to or during delivery (stillbirths) are most commonly caused by anoxia These may be associated with:

 

1. Placental insufficiency - usually evidence of IUGR; deaths may be avoidable by careful monitoring and early delivery when indicated

 

2. Abnormalities of labour and delivery,

 

                                                               i.      such as breech presentation and prolonged labour

 

3. Umbilical cord problems

                                                               i.      prolapse of the cord carries a high risk of fetal death

                                                             ii.      knots or loops only if theu are very tight and no other apparent cause is found

 

4. Antepartum hemorrhage

                                                               i.      Especially abruptio placenta

                                                             ii.      Placenta previa and vasa previa

 

5. Maternal disease, especially diabetes

 

Neonatal death

 

Early neonatal deaths are most commonly related to:

 

1. Pre-term delivery - respiratory distress syndrome and intraventricular hemorrhage
2. Congenital malformations

                                                               i.      Extensive lesions of the CNS

                                                             ii.      severe cyanotic congential heart disease, esp. hypoplastic left heart syndrome

                                                            iii.      Pulmonary hypoplasia (Potter syndrome, diaphragmatic hernia)

 

3. Infections -overwhelming (group B streptococcal infection is most common cause)
4. Intrapartum asphyxia or trauma