3 steps of hemostasis
platelet plug fomation
the ability to minimize blood loss
4 steps of platelet plug formation
- platelet activation
- platelet aggregation
- platelet plut
vonWillebrand factor (vWH)
holds platelets up to the exposed collagen
platelets release chemical messages to get more platelets to come (ADP, seratonin, thromboxane, A2)
a bunch of platelets come together to plug up the exposed area
secreted by neighboring, healthy cells so that platelets only aggregate in the correct area
activated when surface contact-turns into activated 12a
what is thrombin’s key function?
turn fibrinogen into fibrin (active form)
breakdown of a clot and resorbtion of the clot
enzyme responsible for the breakdown of fibrin
normal platelet count
-not a measure of function
why is the patient bleeding?
platelet bleeding problems may be seen with
petechiae, ecchymosis or purpura
low platelet count
reasons why platelets may not be working
genetic disorders (rare)
vWF (can’t bind without it)
BT (higher it is, the longer you bleed)
-not used anymore
normal range PT (prothrombin time)
what does the PT measure?
extrinsic and common pathways
(5, 7, 10, 2 and 1)
-INR (intl normalized ratio)
-used to monitor coumadin
increased PT time values may indicate
vitamin K deficiency and liver disease
vitamin K deficiency can be caused by
bile duct obstruction
liver disease affects coagulation in that
vitamin K is used by the liver to make the clotting factors and bile salts are also used and formed in the liver
normal values for the aPPT
what does the aPPT measure?
intrinsic and common pathway
(12, 11, 9, 8, 10, 5, 2, 1)
-used to monitor heparin therapy
what conditions would cause a prolonged aPPT?
hemophilia A (missing factor 8) hemophilia B (missing factor 9) biliary obstruction (no vitamin K absorbed) hepatocellular diseases
normal ranges for fibrinogen
what is fibrinogen used for?
diagnose fibrinogen disorders or inhibitors of thrombin
-also to diagnose problems with fibrinolysis
when might fibrinogen be increased?
normal ranges of TT (thrombin time)
-measures common pathway
tissue factor pathway inhibitor
acts on the common pathway to control the clot
bleeding differential diagnosis
CALFDIPS cirrhosis and coumadin aspirin leukemia factor definciency (hemophilia) disseminated intravascular coagulopathy idopathic thrombocytopenic purpura (ITP) platelet deficiency or dysfunction scurvy-vitamin C deficiency
most common inherited congenital bleeding disorder
-clinical presentation is bleeding (nasal, sinus, vaginal, GI, deep tissue bleeding)
what other factor is related to the vWF?
how is DDAVP used?
treat VWD (stimulates release vWF)
main symptom of hemophilia
-hematoma of the joints
expected lab results for hemophilia
aPPT will be high
PT will be low
fibrinogen degradation products
how does aspirin prevent clotting?
kills platelet function for the life of the platelet
how do NSAIDS prevent clotting?
deactivate platelet, but function returns w/in 24 hours
what is the main symptom of hemophilia a or b?
what are the causes of hypercoagulability?
too many platelets
clotting factors not working properly (anticlotting factors)
stasis and surgery