coagulation

Question 1

when serum from defibrinated blood is added to a blood sample what happens?

Answer 1

clotting occurs very quickly because there are activated coagulation factors

Question 2

when dicoumarol is added to blood what happens to clotting?

Answer 2

clotting occurs normally because dicoumarol affects the synthesis of coagulation factors but does not affect those factors already present

Question 3

what happens to clotting when powdered talc is added to blood?

Answer 3

it clots quickly because there is increased surface area to cause activation of the intrinsic pathway

Question 4

what happens to clotting when heparin is added to a blood sample?

Answer 4

it doesn’t clot because heparin binds antithrombin III which in turn inhibits clotting enzymes including thrombin X, IX, XI and XII

Question 5

what happens when heparin and protamine are added to blood?

Answer 5

clotting should occur because protamine is a cation compound that inactivates heparin

Question 6

what happens when sodium citrate is added to blood?

Answer 6

it doesn’t clot because the citrate binds calcium

Question 7

what happens when sodium oxalate is added to blood?

Answer 7

oxalate binds calcium and clotting does not occur

Question 8

what happens when sodium fluoride is added to a blood sample?

Answer 8

it binds calcium and clotting does not occur??

Question 9

what happens when EDTA is added to a blood sample

Answer 9

EDTA binds calcium and clotting does not occur

Question 10

what are the three steps of platelet aggregation?

Answer 10

adhesion
activation
aggregation

Question 11

what is the importance of ADP?

Answer 11

it is a potent inducer of activation of platelets

Question 12

how is platelet function evaluated?

Answer 12

by bleeding time

Question 13

what drug prolongs bleeding time?

Answer 13

aspirin. it inhibits cyclooxygenase which prevents prostaglandin production

Question 14

what does dicoumarol do?

Answer 14

it interferes with liver’s utilization of vitamin K. it affects the activities of thrombin (II), VII, IX and X

Question 15

what is vitamin K required for?

Answer 15

the carboxylation of glutamate residues which is important for calcium binding

Question 16

which of factors II, VII, IX and X have the shortest half life and thus will be affected first by dicoumarol?

Answer 16

VII

Question 17

what does the coagulation time capillary tube method involved?

Answer 17

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

Question 18

what is the activated coagulation time?

Answer 18

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

Question 19

what is the activated partial thromboplastin time (APTT)?

Answer 19

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

Question 20

what is one-stage prothrombin time?

Answer 20

it measures factors X, V, VII. it is the gold standard for the EXTRINSIC system. it initiates clotting with tissue thromboplastin (factor III)

Question 21

what is serum?

Answer 21

it does not contain white or red blood cells or clotting factors; serum includes all proteins not used in coagulation

Question 22

what is blood plasma?

Answer 22

it is the yellow liquid component of blod that normally holds the blood cells in suspension; makes approximately 55% of total blood volume

Question 23

what is defibrinated blood?

Answer 23

it is blood in which fibrin has been removed. activated clotting factors are present

Question 24

what is citrated blood?

Answer 24

it is blood in which the calcium has been removed by citrate via precipitation. used for coagulation studies

Question 25

what is bleeding time?

Answer 25

it measures platelet function and can be delayed by aspirin.

Question 26

what is the anticoagulant of choice in coagulation studies?

Answer 26

sodium citrate

Question 27

what are the ingredients in CPDA-1?

Answer 27

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