Wed - Krafts - Hemostasis

Question 1

GP 1a
GP 1b
GP IIb-IIa

what are they and what do they do

Answer 1

GP means glycoprotein
They are found on membranes

GP 1a - binds collagen
GP 1b - binds vWF
First steps in platelet aggregation

GP IIb-IIa - binds fibrinogen - participates in holding platelets together

Question 2

what are the factor names for prothrombin and fibrinogen

Answer 2

factors II and I respectively

Question 3

tissue factor

Answer 3

hidden in cells, but also kinda floats around in the blood. they are little glyco-particles that open up when injury happens

it is the first step in the extrinsic pathway

Question 4

What factor stops the extrinsic arm of the clotting pathway

Answer 4

Xa stops TF and VIIa (extrinsic arm)

Question 5

What does protein C inhibit

Answer 5

inhibits the accelerating factors of clotting, factors VIIIa and Va

Question 6

What does ATIII inhibit

Answer 6

almost all of the clotting factors (except the accelerating factors)

Thrombin
7a,9a,10a,11a

“gives cofactors a big bear hug”

Question 7

TFPI

Answer 7

tissue factor pathway inhibitor

inactivates the extrinsic arm right after it is activated

Question 8

template bleeding time test

what does it truely measure and what does it not measure

Answer 8

BP cuff, make incision, measure time it takes to stop bleeding

measures platelet agrregation, but not coagulation of fibrin (which happens a little later after you actually stop bleeding)

Question 9

Platelet aggregation test

what is it and what do you measure

why do you see a “second wave” of aggregation

Answer 9

to find platelet abnormalities

add aggregating agents to patient’s sample of serum

see if platelets aggregate and fall out of solution

measure decrease in sample turbidity (AKA an increase in transparency)

first wave is the aggregating agent that you put in, second wave is the platelets saying “oh, we are aggregating, ok lets secrete our own aggregating factors”

Question 10

how do you test the coagulation factors in the serum?

AKA coagulation test

Answer 10

trying to figure out how fast patients make fibrin in test tube

draw blood into citrate tube, which takes Ca out of serum. Also, you take the platelets out of the serum

add a factor as see how long it takes to make fibrin

Question 11

PT

when do you order it?

Answer 11

prothrombin time

take patients plasma, add thromboplastin, which makes the extrinsic (!) pathway run, and see how long it takes to clot.

Measuring the effects of factor seven, which is the first thing that coumadin knocks out

don’t order it, do INR (which is a PT normalized against a normal serum)

Question 12

PTT

basically same thing as APTT (activated PTT)

Answer 12

partial thromboplastin time

take out calcium and platelets (this takes out the phospholipids too)

add only a part of the thromboplastin molecule, the phospholipid part, back in. this causes activation of the intrinsic pathway

look at clotting time

Question 13

factor 7

why would you test for this usually?

Answer 13

made by liver, just like all the other factors

needs vitamin k to work, decreased by coumadin

part of the extrinsic pathway

SHORTEST HALF LIFE OF ALL THE FACTORS, IF YOU GIVE COUMADIN, THIS IS THE FIRST ONE TO STOP WORKING so this one is what you test for if you are looking at the effects of coumadin (via the PT test)

Question 14

when do you order an INR

Answer 14

to assess liver function
monitor coumadin
diagnose DIC (disseminated intravascular coagulation)
to assess pre-op status

Question 15

DIC

Answer 15

disseminated intravascular coagulation

widespread clotting in small vessels in the body

Dx by looking at fibrinogen levels (which go down quickly), INR, etc.

Question 16

thrombin time

when would you order it

Answer 16

add thrombin to plasma

you can measure how fast you can make fibrin from fibrinogen

order it if PTT is prolonged and you want to rule out a fibrinogen problem (rare!)

Question 17

PTT mixing study

what is it why do you use it

Answer 17

if patients plasma has prolonged PTT, you add pooled plasma

if the PTT corrects, then they have a clotting factor deficiency (usually 8 (hemophilia a) or 9 (hemophilia b))

if it doesn’t correct, you have an inhibitor (an antibody that messes up the test)

Question 18

what cross-links fibrin

Answer 18

factor 13

Question 19

FDP

Answer 19

degradation products of fibrinogen

this happens on a normal basis, even when you don’t have a clot

Question 20

D-dimers

Answer 20

broken down products of cross-linked fibrin

see a positive d-dimer if you are clotting, but it’s super sensitive to even small little clots, and a positive result doens’t mean much, so its used as a pertinent negative! rules out thrombus.

Question 21

why would you have a decreased amount of fibrinogen

Answer 21

DIC

Massive bleedDIC