coagulation Flashcards
when serum from defibrinated blood is added to a blood sample what happens?
clotting occurs very quickly because there are activated coagulation factors
when dicoumarol is added to blood what happens to clotting?
clotting occurs normally because dicoumarol affects the synthesis of coagulation factors but does not affect those factors already present
what happens to clotting when powdered talc is added to blood?
it clots quickly because there is increased surface area to cause activation of the intrinsic pathway
what happens to clotting when heparin is added to a blood sample?
it doesn’t clot because heparin binds antithrombin III which in turn inhibits clotting enzymes including thrombin X, IX, XI and XII
what happens when heparin and protamine are added to blood?
clotting should occur because protamine is a cation compound that inactivates heparin
what happens when sodium citrate is added to blood?
it doesn’t clot because the citrate binds calcium
what happens when sodium oxalate is added to blood?
oxalate binds calcium and clotting does not occur
what happens when sodium fluoride is added to a blood sample?
it binds calcium and clotting does not occur??
what happens when EDTA is added to a blood sample
EDTA binds calcium and clotting does not occur
what are the three steps of platelet aggregation?
adhesion
activation
aggregation
what is the importance of ADP?
it is a potent inducer of activation of platelets
how is platelet function evaluated?
by bleeding time
what drug prolongs bleeding time?
aspirin. it inhibits cyclooxygenase which prevents prostaglandin production
what does dicoumarol do?
it interferes with liver’s utilization of vitamin K. it affects the activities of thrombin (II), VII, IX and X
what is vitamin K required for?
the carboxylation of glutamate residues which is important for calcium binding
which of factors II, VII, IX and X have the shortest half life and thus will be affected first by dicoumarol?
VII
what does the coagulation time capillary tube method involved?
tubing is broken off every minute and the time when fibrin bridges the broken ends when it is separated by 5mm or more is considered the coagulation time
what is the activated coagulation time?
diatomaceous earth is used as an inert surface activating agent; this shortens the normal clotting time of blood and increases the sensitivity of the coagulation test. not as sensitive as activated partial thromboplastin time
what is the activated partial thromboplastin time (APTT)?
it is the gold standard for the INTRINSIC pathway. citrated plasma is incubated with an activator of factor XII and cephaloplastins to act as platelet phospholipids. the time required to form fibrin after addition of calcium
what is one-stage prothrombin time?
it measures factors X, V, VII. it is the gold standard for the EXTRINSIC system. it initiates clotting with tissue thromboplastin (factor III)
what is serum?
it does not contain white or red blood cells or clotting factors; serum includes all proteins not used in coagulation
what is blood plasma?
it is the yellow liquid component of blod that normally holds the blood cells in suspension; makes approximately 55% of total blood volume
what is defibrinated blood?
it is blood in which fibrin has been removed. activated clotting factors are present
what is citrated blood?
it is blood in which the calcium has been removed by citrate via precipitation. used for coagulation studies
what is bleeding time?
it measures platelet function and can be delayed by aspirin.
what is the anticoagulant of choice in coagulation studies?
sodium citrate
what are the ingredients in CPDA-1?
citrate, phosphate, dextrose adenosine
citrate is the anticoagulant
glucose supports ATP generation by glycolytic pathways
adenine enters the PPP pathway for glycolysis
phosphate prevents a fall in pH
