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Disseminated intravascular coagulation
Disseminated intravascular coagulation (DIC) is a pathological process in the body where the blood starts to coagulate throughout the whole body. This depletes the body of its platelets and coagulation factors, and there is a paradoxically increased risk of haemorrhage. It occurs in critically ill patients, especially those with Gram-negative sepsis (particularly meningococcal sepsis) and acute promyelocytic leukemia.
There are a variety of causes of DIC, all usually causing the release of chemicals into the blood that instigates the coagulation.
- Sepsis, particularly with gram-negative bacteria.
- Obstetric complications, with chemicals from the uterus being released into the blood, or from amniotic fluid embolisms, and eclampsia can be causes.
- Malignant cancers, or widespread tissue damage (e.g. burns), or hypersensitivity reactions all can produce the chemicals leading to a DIC.
Although numerous blood tests are often performed on patients prone to DIC, the imporant measures are: full blood count (especially the platelet count), fibrin degradation products or D-dimer tests (markers of fibrinolysis), prothrombin time or INR and fibrinogen levels. Decreased platelets, elevated FDPs or D-dimers, high PT/INR and decreased fibrinogen are markers of DIC.
Various factors can activate the system of coagulation, but the end result is formation of fibrin, a mesh-like protein. The fibrin deposition can block blood vessels, leading to ischemic damage to some tissues. As well as this, red blood cells are damaged as they get shredded by the fibrin, leading to microangiopathic hemolytic anemia (MAHA).
The underlying cause must be treated initially. Anticoagulants are not given, as by now all the coagulation factors and platelets have been used up. These must be replaced, by platelet transfusion and fresh frozen plasma , to restore normal levels.
DIC results in lower fibrinogen (as it has all been converted to fibrin), and this can be tested for in the hospital lab. A more specific test is for "fibrin split products" (FSPs) or "fibrin degradation products" (FDPs) which are produced when fibrin undergoes degradation when blood clots are dissolved by fibrinolysis.
In some situations, infusion with antithrombin may be necessary. A new development is drotrecogin alpha (Xigris®), a recombinant activated protein C product. Activated Protein C (APC) deactivates clotting factors V and VIII, and the presumed mechanism of action of drotrecogin is the cessation of the intravascular coagulation. Due to its high cost, it is only used strictly on indication in intensive care patients.
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