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Clinical Chem - Vic > Ch 14 - Principles of blood coagulation > Flashcards

Ch 14 - Principles of blood coagulation Flashcards

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1
Q

What is hemostasis?

A

the ability of the body’s system to maintain the integrity of the blood and blood vessels

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2
Q

What is the purpose of coagulation?

A

prevent blood/fluid loss and prevent infection from getting in

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3
Q

Coagulation of blood proceeds through 2 phases, what are they?

A

mechanical and chemical phase

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4
Q

What is primary hemostasis or mechanical phase?

A

platelets in circulation are attracted to injured areas and will stick to the site and each other - von Willebrand factor stabalizes the platelet plug
- platelet clumping should be localized to the site of injury

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5
Q

What is secondary hemostasis?

A

clotting factors are proteins in circulation activated by damage to a blood vessel
- trigger each other in sequence to create fibrin

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6
Q

The formation of a stable platelet plug requires?

A

an adequate number of functional platelets in addition to von Willebrand factor

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7
Q

What does fibrin strands do?

A

they form a net around platelet clumps to stabilize them at the site

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8
Q

Secondary hemostasis is also called?

A

chemical hemostasis or the clotting cascade

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9
Q

What is the function of the clotting cascade?

A

the clotting factors needed to form fibrin are determined by the pathway. If clotting factors needed by the pathway are missing or inactivated, the process stops and fibrin strands are not formed

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10
Q

What prevents clotting by interfering with one or more of the clotting factors which prevents the cascade from completing?

A

anti-coagulants

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11
Q

What are microparticles?

A

are membrane-bound cytoplasmic fragments that are released from platelets, leukocytes, and endothelial cells that serve to increase the surface area on which coagulation complexes can form

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12
Q

The initial mechanical phase is initiated by?

A

interactions of negatively charged phospholipid surfaces of cells and platelets or microparticles

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13
Q

What is generated during the initial phase, and this also recuits and activates platelets and inhibits fibrinolysis?

A

A small amount of thrombin

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14
Q

Activated platelets expose ____ on their outer membrane.

A

phosphatidylserine

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15
Q

What is tertiary hemostasis?

A

when the clot is no longer needed, a process is activated which breaks down fibrin. When fibrin mesh is gone, the clot breaks apart

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16
Q

Primary coagulation disorders are ?

A

rare - usually an inherited defect

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17
Q

What are the clinical signs for a primary coagulation disorder that will often appear by 6 months of age?

A

Petechia - pinpoint hemmorage (mucous membranes)
Epistaxis - nose bleed
Melena - bloody stool
prolonged bleeding at injection site or incision site - hemorraging

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18
Q

What is coagulopathy?

A

a condition in which the blood’s ability to clot is impaired

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19
Q

What does Von Willebrand’s disease do?

A

encourages platelet sticking to happen (platelets don’t clump)

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20
Q

Most common coagulopathy is in what animals?

A

doberman , min pin, rabbits, swine

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21
Q

Prothrombin deficiency in what dogs?

A

spaniel, beagle

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22
Q

Factor VII (Proconvertin) deficiency in what dogs?

A

Beagle, Malamute

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23
Q

Factor IX deficiency synonym is?

A

Christmas factor, plasma thromboplastin

24
Q

Factor X ( stuart factor) deficiency in what dogs?

A

Spaniel

25
Q

Factor XI (plasma thromboplastin antecedent) deficiency in what dogs?

A

great pyrenees, spaniel

26
Q

Factor XII (Hageman factor) deficiency in what dogs?

A

poodle shar pei

27
Q

Secondary coagulation disorders result from?

A

decreased production or increased destruction of platelets, nutritional deficiencies, liver disease, toxicity (things ingested (rat poison))

28
Q

What is disseminated intravascular coagulation (DIC)?

A

disease process associated with many conditions, trauma, infectious disease

29
Q

Clinical signs of DIC include?

A

systemic hemmorrhage (bleeding inside body) and thrombosis (forming clotts in wrong places)

30
Q

What are coagulation assays?

A

coagulation panel

31
Q

What assays are included in the coagulation panel?

A

platelet count, tests for fibrinolysis and platelet function, bleeding time, whole blood clotting time, clot retraction testing, activated clotting time (ACL)- faster than whole blood)

32
Q

Coagulation cascade tests include?

A

activated partial thromboplastin time (APTT), prothrombin time (PT), one-stage prothrombin time (OSPT)

33
Q

Platelet counting should always be?

A

manually verified through microscope evaluation of the blood smear

34
Q

Activated clotting time (ACT) does what?

A

evaluates all major clotting factors except VII and requires a diatomaceous earth tube

35
Q

What are the steps when doing a ACT?

A
  1. warm the tube to 37 degrees Celcius or 98.6 degrees Farenheit
  2. start test timer as soon as blood enters the tube
  3. invert and incubate at 37 degrees
  4. Observe at 60 sec and then again every 5 sec until a clot has formed
    Normal result range is 60 - 90 sec
36
Q

Whole blood clotting time does what?

A

tests the intrinsic clotting pathway

37
Q

What are steps when doing whole blood clotting time test?

A
  1. test timing starts as soon as blood is seen in the syringe
  2. 1 mL of blood is transferred into saline-rinsed tubes (3 tubes, 3 mL total)
  3. tubes are warmed to 37 degrees Celcius
  4. tubes are tilted every 30 sec.
  5. timing is stopped when clot appears in the third tube
    Normal results: 2-10 min for dogs
    4 - 15 min for horses
    10 -15 min for cattle
38
Q

Buccal mucosa bleeding time does what?

A

detects abnormalities in platelet function

39
Q

What are the steps when doing a buccal mucosa bleeding time?

A
  1. a lancet is used to make an incision in the mucosal surface of the lip/mouth
  2. the site is blotted until bleeding stops
    Normal results are 1 - 5 min.
40
Q

Clot retraction test does what?

A

evaluates platelets as well as intrinsic and extrinsic pathways

41
Q

What are the steps when doing a clot retraction test?

A
  1. blood is drawn into a plain sterile tube and incubated
  2. tube is examined at 60 min. and again periodically for the next 24 hrs.
    normal results are:
    clotting is evident after 60 min
    clot is retracted after 4 hr
    clot is compact after 24 hr
    (looking for a clot that has pulled away - like a cake pulling away from the pan
42
Q

Fibrinogen determination does what?

A

test is specific to fibrinogen concentration

43
Q

What are the steps when doing a fibrinogen determination?

A
  1. blood is placed in two hematocrit tubes
  2. the tubes are centrifuged
  3. protein for one tube is measured using a refractometer
  4. the second tube is incubated at 58 degrees celcius for 3 min., recentrifuged, and then protein is measured
  5. the difference between the two protein values is the fibrinogen concentration
44
Q

What are some other clotting factor tests that need a special machine or sent out for testing?

A
  • one-stage prothrombin time - evaluates extrinsic pathway
    citrated sample is used
    normal results are
    clotting occurs within 6 - 20 sec
    7 - 10 sec for dogs
  • activated partial thromboplastin time
  • evaluates intrinsic coagulation pathway - uses a special analyzer
45
Q

Fibrin(ogen) degradation products (FDPs) does what?

A
  • form when fibrin/fibrinogen undergoes proteolysis by pasmin D-dimers
  • specific products of fibrin proteolysis; reflective of active clot degeneration - Thrombo-Wellcotest; measures FDPs in-house
46
Q

What is PIVKA?

A

proteins induced by vitamin K absence

47
Q

Vitamin K is required to activate factors?

A

II, VII, IX, X

used to differentiate toxicity form primary hemostatic defects

48
Q

Blood samples use what coagulants?

A

chelates calcium - binds up calcium
EDTA
Oxalates, Citrates, fluorides, prevents prothrombin conversion, heparin - doesn’t work on calcium

49
Q

What are the two main types of sample tubes?

A

clotting, and anticoagulant

different additives are used for different samples or purpose

50
Q

What is the most preferred anticoagulant for most coagulation tests?

A

sodium citrate

51
Q

What type of tube includes heparin?

A

green top tube GTT
sodium and lithium heparin are both available (typically used for chemistry analysis not requiring serum) Used to provide heparinized plasma samples or whole blood, can be also be used for non-mammal whole blood samples - interferes with staining and causes clumping of WBCs, sometimes used for hematology in exotic patients

52
Q

What is EDTA?

A

Ethylenediamine tetraacetic acid, purple/lavender top tube, PTT, LTT, preferred anticoagulant for hematology - maintains cell morphology
- excessive EDTA volume compared to sample size causes cell shrinkages (RBC crenation) and can invalidate analyzer counts

53
Q

Silicone-coating tube is?

A

Red top tube, clot tube, they have silicone coating and may even have a clot activator sprayed on the inside of the tube, used for serum

54
Q

Serum separation gel sample tube is?

A

tiger top tube TTT, marble top tube, serum separator tube SST, causes clotting to occur more quickly; when centrifuged, the gel acts as a barrier between serum and cells to keep the sample separated

55
Q

What is the sodium citrate sample tube?

A

blue top tube BTT; used for coagulation and platelet assessment

56
Q

No additive sample tubes are?

A

clear plastic top, red/light gray top, discard tube. This tube contains no additives and is often used as a pour off tube to separate components form a sample

Clinical Chem - Vic (29 decks)

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