Primary Hemostasis Flashcards
4 Steps of Primary Hemostasis
- Injury/transient vasoconstriction of neural stimulation/endothelil release
- Platelet Adhesion - GpIb R binds vWF (vWF produced by endothelials and platelets)
- Platelet Activation - adhesion causes shape change and release of granules, ADP which causes GpIIb/IIIa expression on platelet surface, TXA2 from COX/AA promoting aggregation
- Platelet Aggregation - Fibrinogen binds GpIIb/IIIa and links platelets.
Temporary plug that stops bleeding until coag cascade can take over
2 Functions of vWF
Bind GpIb on platelets to adhere platelets to endothelium
Stabilize Factor VIII
Measure of Platelet/Primary Hemostasis Function
Bleeding time. Not PT/PTT/INR
ITP (what it is/cause, labs, biopsy, 3 tx)
Anti-GpIIb/IIIa Abs cause splenic mac consumption of complex, commonly due to viral illness
Decreased PC and increased BT, but normal PT/PTT/INR
Increased megarkars on bone marrow biopsy
Treatment: Steroids, IVIG acutely, splenectomy long term
TTP (what it is, labs/smear, pentad)
Inhibition/deficiency of ADAMTS 13 (vWF metalloprotease) so don’t get degradation of vWF multimers, causing increased platelet aggregation and thrombosis but then deficiency because used up
Decreased PC and increased BT, but also schistocytes and increased LDH
Pentad: Nasty Fever Torched His Kidneys - Neurologic symptoms, Fever, Thrombocytopenia, Hemolysis, Renal symptoms
HUS (what it is, triad, association)
Kinda milder form of TTP on same spectrum
Triad: Hemolysis, Uremia, Thrombocytopenia
In kids associated with E. Coli 0157:H7
Bernard-Soulier Syndrome
Defect in GpIb so defect in platelet-vWF adhesion. Normal/low platelet count but increased bleeding time
Glanzmann Thrombasthenia
Defect/decreased GpIIb/IIIa so defect in platelet-platelet aggregation. No platelet clumping, normal platelet count but increased bleeding time
