Disseminated Intravascular Coagulation Flashcards
what does disseminated intravascular coagulation mean?
“Disseminated” means that the condition is systemic or widespread
“intravascular” refers to the involvement of blood vessels
“coagulation” indicates something to do with blood clotting
so DIC is a thrombo-hemorrhagic (both clotting and bleeding) disorder that involves the entire body
what’s the most important thing to remember about DIC?
DIC is not a primary disorder!
It is the manifestation of some underlying disorder. So if you have a patient with DIC, you must search for the underlying cause.
when does DIC start?
when something triggers the coagulation cascade
the “something” might be the release of a procoagulant substance (like tissue factor) into the circulation, or it might be endothelial injury (which releases tumor necrosis factor, known as TNF)
whatever the initiating cause, the coagulation cascade is activated when it shouldn’t be – and it is supercharged, making excessive amounts of unnecessary fibrin in vessels all over the body
what does TNF do?
TNF = tumor necrosis factor
causes endothelial cells to release tissue factor
what’s the overarching mechanism of DIC?
something triggers the coagulation cascade
coagulation cascade is activated when it shouldn’t be – and it is supercharged, making excessive amounts of unnecessary fibrin in vessels all over the body
fibrin lodges in small vessels and combines with platelets to make thrombi
how does DIC also cause hemorrhage?
all the rampant clotting in DIC uses up platelets and coagulation factors, leaving greatly decreased amounts of platelets and factors, which can lead to hemorrhage
then, to make it worse, as the body tries to lyse the clots, fibrin is broken down into fibrin degradation products
fibrin degradation products themselves inhibit clotting and aggravate the bleeding problem
what are the two categories of conditions that cause DIC?
- dumpers = things that dump procoagulants into the blood
2. rippers = things that damage the endothelium
what are things that dump procoagulant substances into the blood and can therefore cause DIC?
- obstetric complications (abruption, amniotic fluid embolism)
- adenocarcinoma - especially really mucinous ones, like pancreatic
adenocarcinoma) - venomous snake bites
- acute promyelocytic leukemia
what are things that damage endothelium and can therefore cause DIC?
- severe, gram-negative, toxin-producing bacterial infection
- trauma or thermal burns
- vasculitis - like systemic lupus erythematosus
in real life, what are the four things that usually cause DIC?
“MOST”
Malignancy
Obstetric complications
Sepsis
Trauma
what is often seen in the blood smears of someone with DIC?
spherocytes & schistocytes and low/no platelets
the fibrin filling the interterior of tiny blood vessels destroys RBCs trying to get through
some RBCs are totally destroyed while others are sliced into two parts that form a spherocyte and a schistocyte
what does a schistocyte look like?
smaller than normal RBCs
pointy rather than round
no central pallor
which anemia is characterized by the presence of schistocytes?
microangiopathic hemolytic anemia
what are the characteristics of DIC?
- microangiopathic hemolytic anemia
2. decreased platelet count
why does DIC have a decreased platelet count?
all the platelets are consumed in the clotting process, they drop out of circulation
so there’s usually very few/no platelets in a DIC blood smear
