Amniotic Fluid Embolism (AFE)


Definition of AFE
•    AFE is a rare obstetric emergency in which amniotic fluid, fetal cells, hair, or other debris enter the maternal circulation, causing cardiorespiratory collapse.

epidemiology
•    The incidence of clinically detectable AFE is low
•     estimated to be 1 in 20,000 to 80,000 live births.
•    Maternal mortality approaches 80%.
•     5%- 10% of maternal mortality in the United States is due to AFE.
•     Of patients with AFE, 50% die within the first hour of onset of symptoms.
•     Of survivors of the initial cardiorespiratory phase, 50% develop a coagulopathy.
•    Neonatal survival is 70%.

•    Current data suggest that the process is more similar to anaphylaxis than to embolism

•     term anaphylactoid syndrome of pregnancy has been suggested
Major causes and factors
•    occurs in obstetric terms or during labor
•     multiparous woman with a large baby
•    a short tumultuous labor 
•     use of uterine stimulants
•    occurred during abortion
•    amnioinfusion
•    Amniocentesis
•    caesarian section
•    placenta accreta
•    ruptured uterus


pathology
•     Amniotic fluid and fetal cells enter the maternal circulation, possibly triggering an anaphylactic reaction to fetal antigens.
•    (1) Clinical symptoms result from mast cell degranulation with the release of histamine and tryptase,
•    (2) Clinical symptoms result from activation of the complement pathway.

•    . Progression usually occurs in 2 phases.
•     phase I:
•     pulmonary artery vasospasm with pulmonary hypertension and elevated right ventricular pressure cause hypoxia.
•     Hypoxia causes myocardial capillary damage and pulmonary capillary damage, left heart failure, and acute respiratory distress syndrome.
•   

•    Women who survive these events may enter phase II.
•    This is a hemorrhagic phase characterized by massive hemorrhage with uterine atony and DIC
•     however, fatal consumptive coagulopathy may be the initial presentation.

Presentation
•    The clinical presentation of AFE is generally dramatic

•    in the late stages , acutely dyspnea  and hypotension with rapid progression to cardiopulmonary arrest

•    In 40% of cases, followed by some degree of consumptive coagulopathy,

•    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.


•    Pulmonary edema: identified on chest radiograph.
•    Cardiac arrest
•    Uterine atony:
•    Fetal bradycardia: In response to the hypoxic
•     Uterine atony usually results in excessive bleeding after delivery.
Differentials
•    Anaphylaxis
•    Aortic Dissection(动脉瘤)
•    Cholesterol Embolism
•    Myocardial Infarction
•    Pulmonary Embolism
•    Septic Shock
Lab Studies
•    Arterial blood gas (ABG) levels: Expect changes consistent with ypoxia/hypoxemia
.
•    Decreased pH levels
•    Decreased PO2 levels
•    Increased PCO2 levels
•    Base excess increased

•    Hemoglobin and hematocrit /Thrombocytopenia is rare/ platelets /
•    Prothrombin time (PT)
•    Activated partial thromboplastin time (aPTT)
•    fibrinogen (Fg)
•    Blood type and screen
•    Chest radiograph
•    A 12-lead ECG
Treatment
•    Administer oxygen to maintain normal saturation.
•    Initiate cardiopulmonary resuscitation (CPR) if the patient arrests.
•    Treat hypotension with crystalloid and blood products.
•    Consider pulmonary artery catheterization in patients who are hemodynamically unstable.

•    Treat coagulopathy with fresh frozen plasma(FFP) for a prolonged aPTT, cryoprecipitate for a fibrinogen level less than 100 mg/dL, and transfuse platelets for platelet counts less than 20,000/mL.
•    Continuously monitor the fetus.
•    Delivery quickly (forceps)


•    Surgical Care: Perform emergent cesarean delivery in arrested mothers who are unresponsive to resuscitation.
•     hemorrhage was controlled with bilateral uterine artery embolization.
Uterine Rupture
•    is one of the most feared complications of pregnancy

•    the fetus, placenta, and a lot of blood extruding into the mother's abdomen

•    from a weak spot in the uterine wall  or uterus scar
epidemiology
•    the risk of uterine rupture was 1 per 625 women who chose repeat cesarean without labor,
•    1 per 192 women who went into labor and tried for VBAC,
•    1 per 129 for those who had their labor induced without prostaglandins (usually with Pitocin)
•     1 per 41 when prostaglandin medications were used for induction
•     When the uterus did rupture, 1 in 18 babies died, and 1 in 23 of the women required a hysterectomy.
Causes and factors
•    previous surgery on the uterus
•    Prior classical cesareans, where the incision is near the top of the uterus
•    prior removal of fibroid tumors
•    any other uterine surgery that went through the full depth of the muscular portion of the uterus,
•    multiple (three or more) prior low transverse cesareans

•    having had more than five full-term pregnancies
•     having an overdistended uterus (as with twins or other multiples),
•    abnormal positions of the baby such as transverse lie
•    the use of Pitocin and other labor-inducing medications like prostaglandins
presentation
•    Most uterine ruptures occur without symptoms and do not cause problems for the mother or fetus.

•    This mild type is only noticed when surgery is required for other reasons.

•    In the most severe form ,  the laceration is large or cuts across the uterine blood vessels
•    the mother may hemorrhage and require a blood transfusion
•     the uterus may not be repairable and must be surgically removed (hysterectomy)
•    Many women will be advised not to get pregnant again, due to the risk of repeated rupture
•     the baby may not survive
•    the mother's life cannot be saved


Signs of uterine rupture

•     severe, localized pain
•     abnormalities of the fetal heart rate
•     vaginal bleeding
•     the vaginal examination may show that the baby is not as low in the birth canal as he had been earlier.
Preventing and Treatment
•    Some uterine ruptures occur before labor and are considered unpreventable.
•    Sudden severe abdominal pain in later pregnancy should be reported
•     Women with risk factors ( prior classical cesareans, deep fibroid excisions, and other major uterine surgeries )should not attempt labor
•     should be scheduled for cesarean usually between 36 and 39 weeks' gestation.

•    If trying for vaginal birth after low transverse cesarean(VBAC), fetal monitoring is important

•     When uterine rupture is diagnosed during labor, an emergency cesarean is performed.

•    Usually the baby's life can be saved.