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2210 Part XII: Hemostasis and Thrombosis Chapter 129: Disseminated Intravascular Coagulation 2211

mild to moderate bleeding manifestations have been observed, but rupture of uterine spiral arteries and detachment of the placenta is still
severe bleeding generally occurs only after surgery or trauma. unknown. Placental abruption is a leading cause of perinatal death.
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Extensive vascular malformation may persist and cause pain, Older multiparous women or patients with one of the hypertensive dis-
probably resulting from thrombosis, and bleeding following trauma, orders of pregnancy are thought to be at highest risk. The severe hemo-
which is related to the localized or generalized consumption of clotting static failure accompanying abruptio placentae is the result of acute
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factors and platelets and hyperfibrinolysis. Graded permanent elastic DIC emanating from the introduction of large amounts of TF into the
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compression, when possible, and low-molecular-weight heparin consti- blood circulation from the damaged placenta and uterus. Amniotic
tute the only effective treatment in such cases. fluid is able to activate coagulation in vitro, and the degree of placental
separation correlates with the extent of DIC, suggesting that leakage of
AORTIC ANEURYSM thromboplastin-like material from the placental system is responsible
An association between aortic aneurysm and DIC is well docu- for the occurrence of DIC. Abruptio placentae occurs in 0.2 to 0.4 per-
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mented. 265,266 In a series of patients with aortic aneurysm, 40 percent cent of pregnancies, but only 10 percent of these cases are associated
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had elevated levels of FDPs, but only 4 percent had significant bleeding with DIC. Different grades of severity are found among those who
and laboratory evidence of DIC. Several factors predispose patients develop DIC, with only the more severe forms resulting in shock and
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with aortic aneurysms to the development of DIC: a large surface area, fetal death. Rapid volume replenishment and evacuation of the uterus is
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dissection, and expansion of the aneurysm. Clinical and laboratory the treatment of choice. Transfusion of cryoprecipitate, fresh-frozen
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signs of DIC should be carefully sought in patients with an aortic aneu- plasma, and platelets should be given when profuse bleeding occurs.
rysm because bleeding may seriously complicate surgical repair of the However, in the absence of severe bleeding, administration of blood
aneurysm. 267,268 The initiation of localized and generalized intravascular components may not be necessary because depleted coagulation factors
coagulation can be ascribed to activation of the TF pathway by the abun- increase rapidly following delivery. Heparin or antifibrinolytic agents
dant amounts of TF present in atherosclerotic plaques. When patients are not indicated.
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present with significant bleeding or when surgery is planned, hemostatic
defects should be sought and ongoing coagulation activation may be Amniotic Fluid Embolism
corrected by (low-molecular-weight) heparin. Stent-grafting, which is This rare catastrophic disorder, described by Steiner and Lushbaugh in
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a common procedure for repair of aortic aneurysms, was complicated by 1941, occurs only in one in 8000 to one in 80,000 deliveries. A mater-
DIC and death in two patients, of whom one had cirrhosis and the other nal mortality rate of 86 percent was reported in a 1979 review of 272
underwent a lengthy procedure. However, a study of 31 such patients cases, but in a later population-based study, the maternal mortality
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failed to detect DIC following stent-grafting of thoracic aneurysms. 272 (26.4 percent) was significantly lower. 284,285 Patients predisposed to
amniotic fluid embolism are multiparous women whose pregnancies
TRANSFUSION REACTION are postmature with large fetuses and women undergoing a tumultuous
DIC accompanies incompatible blood transfusion, in which massive labor after pharmacologic or surgical induction. Apparently, amniotic
fluid is introduced into the maternal circulation through tears in the
hemolysis is commonly associated with excessive bleeding with wide- chorioamniotic membranes, rupture of the uterus, and injury of uterine
spread thrombosis in fatal cases (Chap. 138). The trigger of DIC in veins. The trigger of DIC probably is TF present in amniotic fluid. 286,287
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these cases cannot be simply ascribed to the release of red cell stroma, The mechanical obstruction of pulmonary blood vessels by fetal debris,
as patients with massive oxidative hemolysis because of glucose-6- meconium, and other particulate matter in the amniotic fluid enhances
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phosphate dehydrogenase deficiency do not develop DIC. Rather, local fibrin–platelet thrombus formation and fibrinolysis. The extensive
extensive antigen–antibody reaction appears to cause DIC as a result of occlusion of the pulmonary arteries and an acute anaphylactoid response
release of elastase and TNF-α from neutrophils, and activation of mono- reminiscent of severe systemic inflammatory response syndrome pro-
cytes that release TNF-α express TF and complement, with assembly of voke sudden dyspnea, cyanosis, acute cor pulmonale, left ventricular dys-
the membrane attack complex inflicting damage to endothelial cells. 274,275 function, shock, and convulsions. These symptoms are followed within
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DISSEMINATED INTRAVASCULAR minutes to several hours by severe bleeding in 37 percent of patients.
Hemorrhage is particularly severe from the atonic uterus, puncture sites,
COAGULATION DURING PREGNANCY gastrointestinal tract, and other organs. The best prospect for decreas-
Pregnancy predisposes patients to DIC for at least four reasons: (1) ing mortality lies in early termination of parturition in patients at high
pregnancy itself produces a hypercoagulable state, manifested by evi- risk and prevention of hypertonic and tetanic uterine contractions dur-
dence of low-grade thrombin generation, with elevated levels of fibrin ing labor. When the syndrome is recognized, immediate termination of
monomer complexes and fibrinopeptide A; (2) during labor, leakage of pregnancy under pulmonary and cardiovascular support is essential.
TF from placental tissue into the maternal circulation causes a hyper-
coagulable state; (3) pregnancy is associated with reduced fibrinolytic Preeclampsia and Eclampsia
activity because of increased plasma levels of PAI-1; and (4) pregnancy Thrombocytopenia described in early reports of eclampsia and wide-
is associated with a decline in the plasma level of protein S. DIC may spread deposition of fibrin in blood vessels observed in fatal cases were
be difficult to diagnose during pregnancy because of the high initial interpreted as evidence of DIC triggered by placental TF exposure to
1
levels of coagulation factors such as fibrinogen, factor VIII, and factor the circulation. A critical analysis of the literature concluded that the
VII. 276,277 Progressive reductions in these factors, however, can confirm thrombocytopenia in these patients stems from endothelial injury rather
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or exclude the diagnosis of DIC in suspected cases. Thrombocytopenia than DIC. However, other investigators provided evidence for signifi-
may be particularly helpful in determining whether DIC is present, pro- cant DIC in preeclampsia and eclampsia. 289,290 Moreover, in a large series
vided other causes of thrombocytopenia are excluded. 278 of patients, a good correlation was noted between the clinical severity
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and abnormalities in platelet counts and FDPs. Also consistent with
Abruptio Placentae DIC were results of assays of sensitive parameters of thrombin gener-
The dramatic clinical presentation of abruptio placentae was first ation and activation of fibrinolysis, such as TAT complexes, D-dimer,
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reported by DeLee in 1901, but the immediate cause of sudden and fibrinopeptide Bβ1–42. Despite these observations, administration

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