Disseminated intravascular coagulation

Pathological process characterised by generalised intravascular activation of the haemostatic mechanism producing widespread fibrin formation, resultant activation of fibrinolysis, and consumption of platelets/coagulation factors (esp I, II, V). Usually the result of serious underlying disease but may itself become life threatening (through haemorrhage or thrombosis). Mortality in severe DIC may exceed >80%. Haemorrhage usually the dominant feature and is the result of excessive fibrinolysis, depletion of coagulation factors and platelets and inhibition of fibrin polymerisation by FDPs. Wide range of disorders may precipitate DIC.

Pathophysiology—DIC may be initiated by

• Exposure of blood to tissue factor (e.g. after trauma).

• Endothelial cell damage (e.g. by endotoxin or cytokines).

• Release of proteolytic enzymes into the blood (e.g. pancreas, snake venom).

• Infusion or release of activated clotting factors (factor IX concentrate).

• Massive thrombosis.

• Severe hypoxia and acidosis.

Causes of DIC

Tissue damage (release of tissue factor) e.g. trauma (esp brain or crush injury), thermal injury (burns, hyperthermia, hypothermia), surgery, shock, asphyxia/hypoxia, ischaemia/infarction, rhabdomyolysis, fat embolism.

Complications of pregnancy (release of tissue factor) e.g. amniotic fluid 512 embolism, abruptio placentae, eclampsia and pre-eclampsia, retained dead fetus, uterine rupture, septic abortion, hydatidiform mole.

Neoplasia (release of tissue factor, TNF, proteases) e.g. solid tumours, leukaemias (esp. acute promyelocytic).

Infection (endotoxin release, endothelial cell damage) e.g. Gram -ve bacteria (e.g. meningococcus), Gram +ve bacteria (e.g. pneumococcus), anaerobes, M tuberculosis, toxic shock syndrome, viruses (e.g. Lassa fever), protozoa (e.g. malaria), fungi (e.g. candidiasis), Rocky Mountain spotted fever.

Vascular disorders (abnormal endothelium, platelet activation) e.g. giant haemangioma (Kasabach-Merritt syndrome), vascular tumours, aortic aneurysm, vascular surgery, cardiac bypass surgery, malignant hypertension, pulmonary embolism, acute MI, stroke, subarachnoid haemorrhage.

Immunological (complement activation, release of tissue factor)

anaphylaxis, acute haemolytic transfusion reaction, heparin-associated thrombocytopenia, renal allograft rejection, acute vasculitis, drug reactions (quinine).

Proteolytic activation of coagulation factors e.g. pancreatitis, snake venom, insect bites.

Neonatal disorders e.g. infection, aspiration syndromes, small-for-dates infant, respiratory distress syndrome, purpura fulminans.

Other disorders e.g. fulminant hepatic failure, cirrhosis, Reye's syndrome, acute fatty liver of pregnancy, ARDS, therapy with fibrinolytic agents, therapy with factor IX concentrates, massive transfusion, acute intravascular haemolysis familial ATIII deficiency, homozygous protein C or S deficiency.

Clinical features

Acute (uncompensated) DIC

Rapid and extensive activation of coagulation, fibrinolysis or both, with depletion of procoagulant factors and inhibitors and signifi cant haemorrhage.

Chronic (compensated) DIC

Slow consumption of factors with normal or increased levels; often asymptomatic or associated with thrombosis.

0 0

Post a comment