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Hemostasis > Section 3 Vascular/Plt Testing > Flashcards

Section 3 Vascular/Plt Testing Flashcards

1
Q

Purpose of capillary fragility (tourniquet) test

A
  • Evaluates vascular integrity
  • Used to test for Dengue viral infection
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2
Q

Capillary fragility test procedure

A
  1. Examine arm and back of hand for pre-existing petechiae
  2. Apply BP cuff
  3. Apply pressure midway between systolic and diastolic pressures
  4. Leave cuff on for 5 min
  5. Remove cuff and wait 5-10 min
  6. Count petechiae on forearm half inch before cuff and just above wrist, may also use back of hand
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3
Q

Total adult blood volume

A

4-6 L

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4
Q

Plasma components

A

Water, proteins, salts, hormones

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5
Q

EDTA tube principle

A

EDTA chelates calcium needed for blood to clot (anti-coagulant function)

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6
Q

Potential issues with EDTA tube

A
  • EDTA clumpers
  • Platelet satellites
  • Cold platelet antibodies
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7
Q

Most commonly used tube in hemostasis

A

Sodium citrate light blue top tube

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8
Q

Sodium citrate tube

A
  • Binds calcium
  • Must have full tube 1 part citrate 9 parts blood
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9
Q

Sodium citrate tube CBC report

A
  • Only WBC and plts
  • Multiply all values by 1.1 df
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10
Q

PPP vs PRP

A

PPP = platelet poor plasma
PRP = platelet rich plasma

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11
Q

Both EDTA and sodium citrate tubes show abnormally low platelet counts. What is happening?

A

Cold platelet antibodies

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12
Q

How do you handle a patient’s blood sample with 55% < Hct < 65%, in relation to anticoag added?

A

Remove 0.1 ml citrate anticoag from 3 ml tube and don’t perform 1.1 df calc

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13
Q

How do you handle a patient’s blood sample with Hct > 65%?

A

Use formula to calculate for amount of citrate anticoag to add

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14
Q

Plt < 50 X 10^3 implications

A

May have issues with surgery

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15
Q

Plt < 10 X 10^3 implications

A

May have spontaneous bleeding

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16
Q

OHSU critical values

A
  • Plt < 30 X 10^3/mm^3
  • Plt > 1000 X 10^3/mm^3
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17
Q

Platelet effectiveness

A

More dependent on function than numbers

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18
Q

Describe platelet inhibition

A

Endothelial cells produce PGI2, which reverses platelet activation
Platelet activation can’t be reversed after alpha granule release

19
Q

How do you measure immature platelet fraction (IPF)?

A
  • Use fluorescent stains and flow cytometry
  • More immature, more fluorescence
  • Reflects reticulated platelets (containing RNA) in peripheral blood
20
Q

Meaning of low to normal IPF

A
  • Decreased production
  • Aplastic anemia, leukemia, BM suppression, drug effect
21
Q

Meaning of increased IPF

A
  • Platelet destruction
  • ITP, TTP, DIC, drug effect…etc
22
Q

Platelet function overall steps

A
  1. Tissue injury
  2. Adhesion to collagen
  3. Shape change
  4. Platelet aggregation
  5. Secretion
  6. Primary hemostatic plug
23
Q

Purpose of bleeding time test

A

Evaluates platelet function and numbers only, not dependent on coag cascade

24
Q

Bleeding time reference range

A

2-9 min

25
Q

Describe the analyzer that replaced the bleeding time test

A
  • Platelet function analyzer (PFA) tests primary hemostasis in artificial vessel simulating the in vivo process of plt adhesion, activation, and aggregation
  • Tests whole blood
  • Test cartridges with collagen/ADP or collagen/epinephrine
26
Q

Closure time (PFA-100) purpose

A

Screens platelets for ability to adhere and aggregate under in vitro capillary flow conditions

27
Q

What affects plt activation?

A
  • RBC and plt counts
  • Times may be prolonged with Hct < 35% or plt < 150k
28
Q

What are the normal, plt defect/vWF disease, and aspirin closure times for COL/ADP?

A
29
Q

What are the normal, plt defect/vWF disease, and aspirin closure times for COL/EPI?

A
30
Q

Describe optical aggregometry (light transmittance)

A
  • It’s a reference method where aggregating agent is added to PRP (PPP is used as blank)
  • Plasma becomes clearer (decreased turbidity) as platelets aggregate, so light transmitted increases
31
Q

Principle of aggregometry

A
32
Q

What mediates secondary aggregation in aggregometry?

A

Release reaction (granules dumped into solution)

33
Q

Show primary and secondary aggregation

A
34
Q

List platelet agonists (aggregating agents)

A
  • ADP
  • Epinephrine/norepinephrine
  • Collagen
  • Thrombin
  • Arachidonic acid
  • Ristocetin
35
Q

Which agonists are mostly biphasic?

A
  • ADP
  • Epinephrine/norepinephrine
  • Thrombin
  • Arachidonic acid
  • Ristocetin
36
Q

Single phase with lag phase plt agonist

A

Collagen

37
Q

Why is ristocetin associated with primary agglutination instead of aggregation like the other agonists?

A

Because it uses vWF to stick plts together via GpIb instead of fibrinogen via GpIIb/IIIa

38
Q

List factors that affect plt aggregation

A
  • pH (8.0 best)
  • Temp (37C)
  • Stirring constant
  • Time at least 30 min
  • Cuvette and stir bar size/shape
39
Q

Which patient lifestyle factors increase plt aggregation?

A
  • Exercise
  • Stress
  • Obesity
  • High fat diet
  • Smoking
  • Diabetes mellitus
40
Q

Which patient factors decrease plt aggregation?

A
  • Alcohol
  • Aspirin and other anti-inflammatory drugs
41
Q

Principle of whole blood aggregometry (impedance)

A

Add aggregating agent to whole blood and plts adhere to electrode and one another, which impedes the DC current, thus increase in impedance is directly proportional to platelet aggregation

42
Q

Purpose of platelet luminaggregometry

A

Gives clearer measure of plt secretion so a perfect biphasic curve isn’t necessary

43
Q

Principle of platelet luminaggregometry

A
  • Thrombin used to induce plt secretion
  • As ATP is released with secretion, it oxidizes luciferin-luciferase to generate cold chemiluminescence directly proportional to ATP conc

Hemostasis (10 decks)

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