HEME

Question 1

von Willebrand factor binds to

Answer 1

Glycoprotein Ib and IIb/IIIa receptors on

platelet,

AND

collagen in the subendothelium.

Question 2

von Willebrand factor catalyzes the activation of factor

Answer 2

8

Question 3

What incr in RBC vol is seen with erythropoiten in 1 wk

Answer 3

RBC volume of 200 mL or one blood unit is produced within seven days

Hematocrit, RBC production, and reticulocyte counts are not changed by increasing the amount given. At 3.5 days after injection of EPO, RBC production is increased enough to produce one unit of blood with 200 mL of RBC at the end of the first week

Doubling the dose of EPO to 600 u/kg did not significantly increase RBC production. With a corrected hematocrit, the increase in reticulocyte counts was not useful in assessing the increased erythropoiesis in patients receiving EPO.

In a multicenter trial, there was no correlation between the corrected reticulocyte count and RBC production. It appears that anemic patients who need to be stimulated preoperatively to increase RBC production also require intravenous iron for the maximal response.

Question 4

During platelet activation

Answer 4

granules release their contents and membranes are exposed that are rich in receptors for fibrinogen, Von Willebrand factor (vWF),
factor Va
factor VIIIa,
and ADP.

Platelet activation leads to the release of:

arachidonic acid metabolites such as thromboxane A2,

Question 5

Platelets adhere to exposed subendothelium by binding to von Willebrand factor via

Answer 5

glycoprotein 1b.

Question 6

The thrombin–thrombomodulin complex activates

Answer 6

protein C,

which inactivates factor Va and VIIIa.

Thrombin stimulates platelet degranulation; ADP released from dense granules stimulates platelet aggregation.

Question 7

Heparin binds to

Answer 7

antithrombin III.

Question 8

Thrombin

Answer 8

not only produces fibrin

but also down regulates (DONT BE FOOLED BY THE NAME!) the coagulation cascade by binding to thrombomodulin on the endothelial cell surface.

potent platelet agonist,

stimulating platelet aggregation,

chemoattractant for monocytes.

By binding to monocytes, thrombin induces the release of interleukin 1(IL-1), causing a number of substances [including plasminogen-activator inhibitor 1 (PAI-1), which depresses activity of the fibrinolytic system] to be synthesized (30)

Question 9

Antithrombin III deficiency

Answer 9

venous thrombotic events.

Antithrombin III is a serine protease inhibitor of thrombin and factors Xa, IXa, and XIa.

Because one of the main actions of heparin is to potentiate the anticoagulant effects of antithrombin III, a patient with this deficiency usually has thrombosis while taking heparin or has an inability to achieve adequate anticoagulation with heparin. A

ntithrombin III deficiency can be either congenital (1 in 2,000 to 5,000 births) or acquired.

Acquired defects occur with inadequate production, as in liver disease, malignant disease, nephrotic syndrome, disseminated intravascular coagulation, malnutrition, or increased protein catabolism.

Thrombotic episodes are related to predisposing events such as operations, childbirth, and infections. Once the diagnosis of antithrombin III deficiency is established, fresh frozen plasma is administered and is followed by long-term treatment with warfarin.

Question 10

Platelets are viable in the blood bank up to

Answer 10

5 days after collection,

need to be stored at room temperature.

Question 11

After disruption of the integrity of the vessel wall, platelets adhere to the subendothelium through

Answer 11

their surface membrane

glycoprotein receptor Ib

that attaches platelets to

von Willebrand factor (vWF).

Subsequently, the platelet becomes activated, resulting in expression of the platelet membrane surface receptor

glycoprotein IIb/IIIa

allowing platelets to aggregate.

Platelets also may be activated by

thrombin

via activation of

protease-activated receptors on the cell membrane of the platelet.

Question 12

Platelet aggregation is inhibited by both

Answer 12

cyclooxygenase 1 and 2 inhibitors

these inhibitors irreversibly inactivate

thromboxane

and

prostaglandin production.

Question 13

Platelet activating factor (PAF) is a

Answer 13

potent phospholipid activator and mediator of leukocyte functions:

platelet aggregation

degranulation,

inflammation,

and

anaphylaxis

and causes vasodilation.

Question 14

ADP effect on platelets

Answer 14

ADP stimulates platelet shape change and aggregation.

It requires the ability of the platelet to synthesize prostaglandins

and is hence inhibited by aspirin.

Question 15

Protein C is synthesized in the

Answer 15

liver,

and it is dependent on vitamin K for carboxylation.

Question 16

Activated protein C’s primary function is the inactivation of

Answer 16

coagulation factors Va and VIIIa,

which in turn will inhibit thrombin generation and

factor X activation.

Acitvated protein C also neutralizes

plasminogen-activator inhibitor-I,

which then facilitates fibrinolysis.

The effects of protein C is further potentiated by protein S, another vitamin K-dependent protein which serves as a co-factor.

Many factors contribute to a patient’s hypercoagulable state. Studies screening large number of donors have demonstrated that asymptomatic protein C deficiency is relatively common.