Approach Considerations
On chest radiographs, posteroanterior and lateral findings are usually nonspecific, but evidence of pulmonary edema may be observed.
Place an arterial line to accurately measure blood pressure and to obtain arterial blood gas (ABG) readings. Place a pulmonary artery catheter to monitor wedge pressure, cardiac output, oxygenation, and systemic pressures.
Laboratory Studies
There are no laboratory tests to either confirm or refute the diagnosis of AFE. [26] Laboratory values are useful in providing supportive measures for the patient.
Arterial blood gas (ABG levels
Expect changes consistent with hypoxia/hypoxemia, such as the following:
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Decreased pH levels (reference range = 7.40-7.45)
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Decreased PO2 levels (reference range = 104-108 mm Hg)
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Increased PCO2 levels (reference range = 27-32 mm Hg)
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Base excess increased
CBC with platelets
Hemoglobin and hematocrit levels should be within reference ranges.
Thrombocytopenia is rare. If platelets are less than 20,000/µL, or if bleeding occurs and platelets are 20,000-50,000/µL, transfuse platelets at 1-3 U/10 kg/d.
Coagulation studies
Prothrombin time (PT) is prolonged because clotting factors are used up. Values are institution specific, but intervention is indicated when the PT is 1.5 times the control value. Administer fresh frozen plasma (FFP) to normalize the PT.
Activated partial thromboplastin time (aPTT) may be within reference ranges or shortened.
Rotational thromboelastometry (ROTEM) has been used as a point of care test to guide management of the coagulopathy. [27]
Fibrinogen level
If fibrinogen level is less than 100 mg/dL, administer cryoprecipitate. Each unit of cryoprecipitate raises the fibrinogen level 10 mg/dL.
Type and screen
Blood type and screen in anticipation of the requirement for a transfusion.
Electrocardiography
A 12-lead ECG may show tachycardia, ST segment and T-wave changes, and findings consistent with right ventricle strain.
Histologic Findings
On autopsy, blood vessels in the lungs may show evidence of fetal debris (eg, squamous cells, vernix, mucin).
Aguilera et al [28] reported fetal epithelial squamous cells obstructing 80% of pulmonary capillaries and fetal epithelial squamous cells in the alveoli on autopsy. A blood sample from a central venous catheter also showed fetal squames. Another study by Koike et al reported that serum squamous cell carcinoma antigen levels were significantly higher in women with AFE than those in healthy controls. [29]
Marcus et al [9] found focal interstitial hemorrhages in the kidneys, the left ventricle, and the interventricular septum. Alcian blue periodic acid-Schiff (PAS) stain was positive for mucin in the vasculature and oil red O stain for lipid was positive in the lungs.
Hankins and colleagues [30] reported on goats injected with fresh amniotic fluid (n=8), filtered amniotic fluid (n=14), and meconium-stained fluid with solid debris (n=7). The animals were euthanized 3 hours after the procedure and samples of the lungs were taken. Amniotic fluid debris was found in 7 out of 7 of the meconium-stained group, 2 out of 8 of the fresh fluid group, and 1 out of 14 of the filtered group. Hankins et al concluded that, in this model, histopathologic confirmation of AFE was unreliable except in cases involving meconium-stained fluid.
Kobayashi et al [31] used antibody TKH-2, which reacts with meconium and the mucin derived from amniotic fluid (glycoprotein) to stain the lung tissue of women with AFE. TKH-2 immunostaining appears to be a sensitive method of detecting mucin in the lungs of women suspected of having an amniotic fluid embolus.
Tables
| SCORE | 0 | 1 | 2 |
|---|---|---|---|
| Platelets | >100,000/mL | < 100,000/mL | < 50,000/mL |
| Prothrombin time or INR | < 25% increase | 25-50% increase | >50% increase |
| Fibrinogen | >200 mg/L | < 200 mg/L |
