DISSEMINATED INTRAVASCULAR COAGULATION

“DIC”

Critical patient at Washington State University Veterinary Teaching Hospital (Photocredit: youtube.com/watch?v=814XMfvSAgg, WASU College of Veterinary Medicine)

Disseminated intravascular coagulation is an extreme complication of numerous already life-threatening conditions leading to the deregulation of the body’s natural mechanisms of blood clotting and blood clot dissolving. DIC is a disease of the blood but it does not happen alone. An inflammatory condition has to start it off by initiating the body's natural clotting mechanisms. After all the clotting factors are consumed in this widespread process, there are no clotting factors left and uncontrolled bleeding results.

SETTING THE SCENE FOR DIC

In the normal body, there are small bleeds occurring regularly as we bump into things or cut ourselves. Small blood vessels tear exposing an inner substance called "tissue factor." Tissue factor initiates a blood clotting cascade involving assorted blood proteins such that blood clots (made of a protein called "fibrin") form and patch these small blood vessel tears. Bleeding stops and the clots become stronger and more permanently bound to the injury. Eventually, the healing process involves replacing the clot with scar tissue and the original tissue tear is patched up nearly as good as new.

In disease conditions where there is a great deal of tissue destruction (crushing injury, widespread bacterial infection, cancer, snake bite, etc.), a lot of tissue factor is exposed leading to a lot of activated coagulation. Microclots form all over the body's vasculature float around freely. Eventually they get stuck and plug up small blood vessels so that normal circulation cannot get through. Cells in these tissues begin to die from lack of oxygen. This creates more tissue death and more tissue factor exposure and compounds the problem. It is easy to see where the term "Disseminated Intravascular Coagulation" comes from.

Eventually there is so much clot activation that clotting factors are used up. Without the normal clotting mechanisms in place, spontaneous bleeding results. Unless the underlying cause of the tissue destruction can be controlled, death is common.

Typical conditions that are associated with DIC include those involving dying internal tissue, widespread inflammation, red blood cell destruction, poor circulation, particulate matter in the bloodstream, or loss of blood vessel integrity. Some of the more classic conditions are listed below:

DIC is primarily a canine problem but can occur in the cat.

The usual underlying causes in feline patients are
lymphoma, hepatic lipidosis, and feline infectious peritonitis.

RECOGNIZING DIC

The sooner DIC is recognized, the more likely the chance of a positive outcome. At first, there are no signs at all, just subtle blood test changes. It is important for the medical staff to watch for these lab changes in patients known to have diseases associated with DIC.

There are several factors that go into the diagnosis of DIC and a patient need not have them all:

• Low platelet count
  Platelets are the white blood cell fragments that are involved in normal blood clotting. In DIC, they are depleted.
• Evidence of inappropriate bleeding
  This could be bruising in the skin, excessive bleeding after a blood sample is taken, or spontaneous bleeding from the gums or from any orifice.
• Increases in Blood Clotting Times
  Tests called the PT and PTT are run to assess how long different blood clotting proteins take to produce a blood clot. These times are compared to standardized “normal” times. Increased clotting times indicate a tendency to bleed inappropriately. Clotting times well below the normal range can indicate a hypercoagulable state.
• Presence of Fibrin Degradation Products (sometimes called “fibrin split products”)
  Fibrin is the material that clots are made of. When antithrombin and other biochemicals remove clots, fibrin fragments become detectable. These are fibrin degradation products. A fibrin degradation product of note is called the “D-Dimer.” It is notable because there are in-hospital test kits that can be used to detect it. The presence of D-dimer definitely indicates that a clot has been made and broken down (though, there are many reasons for such a thing to have occurred other than DIC).
  

The absence of D-Dimer rules out DIC with 95% confidence in dogs but is less reliable in cats.

• Reduced Fibrinogen blood levels

Fibrinogen is a fibrin precursor and its absence suggests depletion. The use of fibrinogen reduction as a marker for DIC has been questioned because there are numerous other factors that can reduce fibrinogen.

A SPECIAL NOTE ON THROMBOELASTOGRAPHY ("TEG" TESTING) - In this kind of testing a gadget called a thromboelastograph hemostasis analyzer accepts a sample of blood, forms a clot with it, and measure the strength and elasticity of the clot. The test determines if there is an excessive tendency to clot or a reduced tendency to clot. Dogs with reduced ability to clot on the TEG test have a much higher mortality rate. This test may help determine the prognosis with DIC at least in dogs.

TREATMENT

Ultimately what all this clotting and bleeding comes down to is loss of blood flow to the tissues and treatment centers on restoring normal circulation. This means intravenous fluid administration is crucial to restore tissue perfusion. In the past, heparin (an anticoagulant) was used to treat DIC as well as plasma transfusions. These treatments have become more controversial. There is no definitive treatment for DIC beyond maintaining tissue perfusion with fluids and general critical patient support.

The most significant factor in the treatment of DIC is removal of the original disease that predisposed the patient to DIC in the first place. If this can be achieved, it would be the best chance at resolving DIC.

Page posted: 3/25/2009
Page last updated: 5/25/2023