Fibrinolytic system: Plasmin
Plasmin – leaves crumbs – its breaks down things (fibrinogen, fibrin, coagulation factors) – think
fibrinoLYTIC system. When it breaks down a clot, there are many pieces (ie fibrin) left around, which are
fibrin degradation products.
What is the single best screening test for DIC? D-dimers (better answer) or fibrin split products. What
plasmin does is breaks things apart, leaving crumbs behind and you have degradation products. D
dimers are the absolute best test for DIC (di- means 2). When you form a fibrin clot, factor 13 (fibrin
stabilizing factor) makes the clot stronger. How do you stabilize strands? Link them by putting
connections between them to make them stronger (this is what factor 13 does). So, how do you make
collagen stronger? By, linking them to increase the tensile strength (factor 13 will put a crossbridge in
fibrin). What D-dimer is detecting are only those fibrin factors that have a link (ie when there are two of
them held together, this what the test picks up). What does this absolutely prove? That there is a fibrin
clot. Do you see this in DIC? Yes.
Example: Would you see it if you broke apart a platelet thrombus in a coronary artery? (Remember a
platelet thrombus is a bunch of platelets held together by fibrin). So, what would the D dimer assay be if
you broke apart that clot? Increased, you would see increased D dimers and would see the little fibrin
strands held together by cross linking. They often do that to see if you have recanalized or if you got rid
of your thrombus.
Example: it is often also seen with a pulmonary embolus, b/c if you have a pulmonary embolus, one test
is a D dimer b/c you will form a clot that will activate the fibrinolytic system, and it will try to start
breaking it down, and there will be a release of D dimers. Single best test for DIC. Good test for picking
up pulmonary embolus, along with ventilation/perfusion scans. Excellent test to see if you have
reperfusion after given t-PA b/c it proves that if D dimers were present, a fibrin clot must be present
(fibrin was there so it proves it).
Senile purpura: Seen on the back of hands of an old person – they hit things and get senile purpura;
vessels get unstable as you get older and subcutaneous tissue thins. When you hit yourself, BV’s
rupture and you get echymoses – called senile purpura, an age dependent finding. Only present in
places that normally hit things, back of the hands and the shins. Example: Mom was put in old age
home and the children were gonna sue the old age home for abuse. Do the children have a case?
No, b/c it has nothing to do with abuse and is an age dependent finding. Example: now if they also
saw echymoses on buttocks and back, this is not a normal place to get trauma related to just
bumping into things – that would be abuse. Senile purpura is the cause of echymoses on the back of
the elderly’s hand. Everyone will get this, everyone, no one is exempt.
Osler Weber Rendu Dz aka hereditary telangiectasias: Many of these pts have chronic Fe def
anemia, related to persistent GI bleeds. You can make the dx with PE of the pt. The pt will have
small red dots called telangiectasias and if you look on the lips and tongue you will see
telangiectasias, and if you do endoscopy, you will see the little red dots thro