Overview of primary hemostasis

1
Overview of primary hemostasis

• ??????? ???

2
I. The mechanism of blood coagulation ??? ???
vascular system?? blood?
fluid state? ? ????? ?? ?? Vasoconstriction -gt
PLT aggregation -gt coagulation Effectiveness of
hemostatic mechanism - type and degree of
injury - ability of vasoconstriction - PLT
availability activity - blood factor
relation to function - absence of inhibitors,
circulating anticoagulants and antagonists
Fibrinolysis the process of dissolution of the
clot Homorrhage or thrombosis
3
(No Transcript)
4
II Primary hemostasis The vascular system

The platelets 1. Vascular system a thin layer
of endothelial cells thromboresistant surface
vascular damage -gt vasoconstriction -gt immediate
reduced blood flow vasoactive substance
(serotonin, thromboxane A2 , endothelin) 2.
Platelets 2-4um in diameter, are produced in
BM from a megakaryocyte, which produces about
2000 PLT 70-80 circulate in blood, 20-30
pool in the spleen life span is 7 to 10 days
5
(No Transcript)
6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
1) PLT number Vs function PLT function is
more relevant than PLT numbers ex) gt 150?
bleeding can be caused by dysfunctional PLT
lt 5? often not bleed lt 1?
spontaneous bleeding may occurs but young PLT
will correct for the
defects2) PLT kinetics Adhesion - adhere
to collagen -gt undergo a shape change from discs
to spheres - primary aggregation and is
reversible
10

• Release
• - dense granules ( ADP, ATP, ionized
  calcium, magnesium, epinephrin,
• phosphate,
  and serotonin)
• - alpha granules ( fibrin, PDGF, PAI,
  fibronectin, albumin, PF3, PF4,
• vWF, fibrinogen, ß
  thromboglobulin, and factor V)- secondary
  aggregation , is irreversible
• Aggregation PLTs cohere to other PLTs
• Stabilization of the clot
• - thrombus formation- release factor V and
  expose PF 3 to accelerate the coagulation
  cascade and promote activation of cloting factors
  -gt stabilze the PLT
• plug with a fibrin clot

11
(No Transcript)
12
III. Evaluation of bleeding in primary
hemostasis1. Abnormalities of the vascular
endothelium Hereditary or
Acquired vascular disorders Ehlers-Danlos,
Homocystinuria Allergic purpura,
Henoch-Schölein purpura Normal vessel
walls provide - a surface resistant to the
formation of thrombi - if disrupted, provide
the initial stimuli for thrombus formation -
inhibitors for PLT activity, activators for
clearance of thrombus
13

• 2. Evaluation of PLT abnormalities1)
  Thrombocytopenia - PLTs are low in number but
  normal in function - immunologic, ITP -
  infection, viral ect - drugs (aspirin)2)
  Thrombocytopathia - poor PF3 activity PLT
  count normal, poor in function - too little PF3,
  due to systemic disease (uremia, scurvy, hepatic
  dz) - failure or release PF3 - deficiency of
  plasma factor- vWF

14

• 3) Thrombocytosis - PLTs are increased in
  number, normal in function- acute hemorrhage,
  hemolysis, postsplenectomy
• 4) Thrombocythemia
• - PLTs increased in number, large, and bizarre
  forms,
• bleeding time prolonged, poor clot
  retraction
• - myeloproliferative disorders

15
VI. Tests to evaluate a bleeding disorder of
primary hemostasis (1) ?? ?? (Bleeding time)
?? ??? ?? ?? ? ??? ??? ??? ??? ?? ??? ??
? ???? ??? ??? ?? ??? ?? ?? ?? Duke?
puncture in the ear lobe ?????
??? ??? ??, ???? ?? 14? 7? ??
aspirin ?? history ??? ??? ???, ????, vWD ?
????? ?? ??? ?? ??, ???? ?? ??? ?? ??,
vWD ?? afibrinogenemia, severe
hypofibrinogenemia
16
(2) PLT aggregation test PLT rich plasma ?
aggregating agents? ??? PLT ??? ?? ?
aggregation ?? gt aggregometer? percent
transmittance? ?? Aggregation agents ADP,
EPI, Collagen, Ristocetin, Arachidonic acid 7?
?? aspirin ?? history ??? Interpretation
- primary curve aggregating agent? PLT? ??????
PLT shape
and small aggregates ?? - secondary wave
complete aggregation
17

• ADP Glanzmanns thrombasthenia
• Collagen Glanzmanns thrombasthenia,
  aspirin-like release
• disorder, storage pool
  disorder, uremia
• Ristocetin vWD, Bernard-Soulier syndrome

18
(No Transcript)
19
(No Transcript)
20
(No Transcript)
21
(3) Capillary fragility test ( tourniquet test
, vascular disorder) Tourniquet test
upper arm? cuff? ?? diastolic ? systolic
pressure? ????? 5?? ??? ?? ??? ? ? ? ??
petechiae ?? ??? ?? 5? ??, 3cm??? ?
???? ??(4) Clot retraction time fibrin
formation, from the inspection of the clot
clot retraction occurs by the interaction between
PLT psuedopods and fibrin strands.
occurs within 60 minutes, and the colt
occupies 50 of total volume of blood.
22
(No Transcript)