4.2-REVISED PRIMARY HEMOSTASIS Flashcards by Dave U.

What is primary hemostasis

Initial response to vascular injury involving blood vessels+platelets to form a platelet plug

How well did you know this?

Not at all

Perfectly

What are the three stages of primary hemostasis

Vasoconstriction+Platelet adhesion to subendothelial connective tissue+Platelet aggregation to form a plug

How well did you know this?

Not at all

Perfectly

What components are involved in primary hemostasis

Blood vessel walls (vascular system)+platelets+See Figure 4.1

How well did you know this?

Not at all

Perfectly

What substances do blood vessels release to inhibit platelet adhesion

Prostacyclin+Adenosine

How well did you know this?

Not at all

Perfectly

What receptor on endothelial cells binds and inactivates thrombin

Thrombomodulin

How well did you know this?

Not at all

Perfectly

What enzyme on endothelial cells converts plasminogen to plasmin

tPA (Tissue Plasminogen Activator)

How well did you know this?

Not at all

Perfectly

What factor is required for platelet adhesion to injured vessels

von Willebrand factor (vWF)

How well did you know this?

Not at all

Perfectly

What does vWF bind to on blood vessels

Subendothelial connective tissue

How well did you know this?

Not at all

Perfectly

What three properties make platelets useful in hemostasis

Adhesiveness+Aggregation+Viscous metamorphosis

How well did you know this?

Not at all

Perfectly

What is “viscous metamorphosis”

Loss of platelet individuality to form large amorphous hyaline–like clumps

How well did you know this?

Not at all

Perfectly

What are the stages of megakaryopoiesis

Megakaryoblast→Promegakaryocyte→Megakaryocyte→Metamegakaryocyte+See Table 4.1

How well did you know this?

Not at all

Perfectly

Which stage of megakaryopoiesis has cytoplasmic granules

Megakaryocyte

How well did you know this?

Not at all

Perfectly

Which stage of megakaryopoiesis has multiple nuclei

Megakaryocyte and Metamegakaryocyte

How well did you know this?

Not at all

Perfectly

What stage shows visibility of platelets

Metamegakaryocyte

How well did you know this?

Not at all

Perfectly

What are the four functional zones of platelets

Peripheral zone+Sol-gel zone+Organelle zone+Membrane system

How well did you know this?

Not at all

Perfectly

What does the peripheral zone of platelets consist of

Glycocalyx+Plasma membrane+Submembrane area

How well did you know this?

Not at all

Perfectly

What glycoprotein binds collagen for platelet adhesion

GpIa+See Table 4.2

How well did you know this?

Not at all

Perfectly

What glycoprotein acts as the vWF receptor+and aids adhesion to subendothelium

GpIb+See Table 4.2

How well did you know this?

Not at all

Perfectly

What glycoprotein binds fibrinogen for platelet aggregation and vWF binding

GpIIb-IIIa+See Table 4.2

How well did you know this?

Not at all

Perfectly

What glycoprotein binds thrombospondin

GpIV+See Table 4.2

How well did you know this?

Not at all

Perfectly

What glycoprotein binds thrombin and aids platelet aggregation

GpVa+See Table 4.2

How well did you know this?

Not at all

Perfectly

What glycoprotein is associated with Ib complex and aids adhesion

GpIX+See Table 4.2

How well did you know this?

Not at all

Perfectly

What zones provides a cytoskeletal system for platelets

Sol-gel Zone+See Figure 4.2

How well did you know this?

Not at all

Perfectly

What three types of granules does the Organelle zone contain

Alpha+Dense bodies+Lysosomes+See Figure 4.2

How well did you know this?

Not at all

Perfectly

What system does the Membrane system contain

Dense tubular system+See Figure 4.2

What agonists activate platelets

ADP+Thromboxane A2+Collagen+Thrombin

What substrate is converted to TXA2 by cyclooxygenase

Arachidonic acid

What are the functions of TXA2

Vasoconstrictor+Stimulates platelet secretion

What do alpha granules secrete

Platelet factor 4+Fibronectin+Beta – thromboglobulin+Plasminogen activator+Thrombospondin+Inhibitor 1+Protein S+Factor V+von Willebrand’s factor+Factor XIII+Fibrinogen+Platelet-derived growth factor (PDGF)

What do dense bodies secrete

Magnesium+Phosphate+Calcium+ADP and ATP+Serotonin/5-HT (hydroxytryptamine)+Epinephrine

Which secreted granules are all involved in coagulation

Calcium+ADP & Serotonin

What is required for platelet aggregation

Fibrinogen+Calcium+GpIIb – IIIa complex

What stimulates platelets to undergo shape change

ADP

What links platelets during aggregation

Fibrinogen binding to GpIIb – IIIa

What is the normal platelet count range

140 – 440 X 10^9/L

How is platelet count estimated on a peripheral blood smear

7- 25 /field+3-10 platelets/100RBC or 5 – 20 platelets/200RBC

What is the formula for estimating platelet count using OIFs

number of platelets counted in 10 OIF x 2

What platelet count is considered markedly decreased

0-49

What platelet count is considered moderately decreased

What platelet count is considered slightly decreased

100

What platelet count is considered low normal

150

What platelet count is considered normal

200

What platelet count is considered slightly increased

401

What platelet count is considered moderately increased

600

What platelet count is considered markedly increased

More than 800

How is platelets described in random sampling of a few OIFs if they are decrease

1 platelet in OIF

How is platelets described in random sampling of a few OIFs if they are normal

several platelets with some clumps

How is platelets described in random sampling of a few OIFs if they are increase

>25 platelets in OIF

What type of blood is used for Direct Method

EDTA blood

What is the specimen of choice under EDTA blood for Direct Method

Tocantin’s Method+Rees & Ecker Method

What reagents are used in Rees & Ecker Method

3.8g Sodium Citrate+0.22mL formaldehyde+0.05g BCB+50mL distilled water

What is the reagents used in Phase Contrast Microscopy Method

1% ammonium oxalate (lyses RBC)+distilled water

Platelets are counted in all 25 small squares within the large center square under which magnification

40x magnification

Under 40x magnification+how should platelets look like when scanned for even distribution

Platelets appear greenish

Which lines should be count when counting cells

Count all cells that touch any of the upper and left lines

Which lines should be ignore when counting cells

do not count any cell that touches a lower or right line

List the direct method

Guy & Leake’s+Phase Microscopy Method+Brecker – Cronkite+Unopette+Nygard’s+Walker & Sweeney’s+Van Allen’s

What fluid does Unopette contain

2ml of diluting

What tube does Unopette contain

small capillary tube prepared to withdraw 10 microliter blood

What should you remember when mixing Unopette

Mix by squeezing gently 2-3 times to rinse the capillary tube+Close the upper opening with your index finger and invert the unit several times to mix the blood sample and the diluent.

What to do after mixing Unopette

Let it stand at room temperature for 10 minutes before charging the hemocytometer.

What should you do with the Inverted reservoir before charging for counting

Invert reservoir and discard the first 3 or 4 drops of mixture.

What to do before placing the hemocytometer on the microscope

Place hemocytometer in moist petri dish with applicator sticks for 10 minutes to allow platelets to settle

What two test does automated platelet counts do

Optical Method+Electrical Method

What is measure in Optical Method

detection of the degree of light scattering

What is measure in Electrical Method

electrical resistance/impedance

Electrical Method is also know as

Coulter counter

What does Ohm’s Law states

Voltage = Current x Resistance

In terms of Electrical Method

what is Voltage size directly proportional to

What is conduct by Isotonic solutions

electricity

What does Number of pulses refers to

number of cells

What does Height of pulse refers to

size of the cell

What does Histograms shows from RBC

MCV+RDW

What does Histograms shows from Platelet

MPV+PDW

What does X-axis refers to

Horizontal (size)

What does Y-axis refers to

Vertical (number)

What do Cytogram or scatterplot measure

internal cell complexity+volume or size

Which measure internal cell complexity in Cytogram or scatterplot

result of side scatter

Which measure volume or size in Cytogram or scatterplot

result of forward scatter

What is the dilution for RBC

0.07638888888888884

What is the dilution for WBC

1:500

What are the sources of error

aperture plugs+bubbles+extraneous electrical pulses+giant platelets

What conditions causes Thrombocytosis

Polycythemia vera+Thrombocythemia+After splenectomy+TB+Secondary anemia

What conditions causes Thrombocytopenia

Pernicious anemia+Aplastic anemia+Acute leukemia+Lesions involving the bone marrow

What is measure in Bleeding Time

vessel integrity+platelet integrity+protein or platelet interaction

What is the normal value for bleeding time

2 – 8 minutes

What are the methods under Bleeding Time

Duke Method+Ivy’s Method+Mielke Method+Simplate / Surgicutt Method

What does Duke Method measure

earlobe or fingertip prick at 3mm deep

What is the normal range for Duke Method

2 – 4 minutes

What device does Ivy’s Method uses

template or commercially available devices that make a standard wound

What are the normal range for Ivy’s Method

2 – 9 minutes

Which method is use Bard-Parker or similar disposable blade + rectangular polystyrene or plastic

Mielke Method

What are the advantages of Mielke Method

the depth of the incision can be controlled

What are the disadvantages of Mielke Method

Patient anxiety due to the open blade+Small scars might form

Which is the preferred method

Simplate / Surgicutt Method

What is the spring activated surgical steel blade which is housed in a plastic unit

Simplate or Surgicutt blade device

What are the advantages of Simplate / Surgicutt Method

instrument is a sterile

What is the critical value for bleeding time

> 15 min

what should you do if the puncture site is still bleeding after 15 minutes

discontinue the test and apply pressure to the site+Document and report the results to the clinician.

What does Copley – Lalitch Immersion Test measures

immerse punctured fingertip in NSS (37⁰C)

What is the normal range for Copley – Lalitch Immersion Test

3 – 6 minutes

What is the principle of Aspirin Tolerance Test

2 tablets can prolong BT of a patient with platelet abnormality+4 tablets prolong BT of a normal individual

How is the Aspirin Tolerance Test procedure

Determine patient’s baseline BT+if BT > 6 mins = not employed+if BT < 6mins = proceed+Give patient 2 tabs aspirin+Determine the patient’s 2nd BT (Duke’s) after 2 hours

What is the meaning if the difference between the 1st and 2nd BT is not >2mins =

normal tolerance to aspirin in Aspirin Tolerance Test

What is the meaning if the difference is >2mins =

low tolerance to aspirin in Aspirin Tolerance Test

What is test in Capillary Fragility test by increased hypoxia and hygrostatic pressure

Test capillary fragility

What are the test results roughly graded in Capillary Fragility test

1+= a few petechiae on the anterior part of the forearm+2+ = many petechiae on the anterior part of the forearm+3+ = much petechiae on the entire forearm and hand

What are the sources of error in platelet counts

Aperture plugs (most common)+bubbles and extraneous electrical pulses cause false increase or positive error+giant platelets cause a false decrease in platelet count

What is thrombocytosis

increase platelet count due to a disease

What is thrombocythemia

increase platelet count of unknown cause

What is thrombocytopenia

decrease platelet count

What conditions increases platelet counts

Polycythemia vera+Thrombocythemia+After splenectomy+TB+Secondary anemia

What conditions decrease platelet counts

Pernicious anemia+Aplastic anemia+Acute leukemia+Lesions involving the bone marrow