The property of circulation whereby blood is maintained as a fluid within the vessels
Four systems of hemostasis ?
- Platelets–Primary Hemostasis
- Coagulation–Secondary Hemostasis
What metabolite induces Vasoconstriction ?
Serotonin and thromboxane A2
What metabolite induces Vasodilation ?
Prostacyclin PG I2
Name the 7 step of the Hemostatic Plug cascade ?
- ) Vascular Injury
- ) Tissue Exposure
- ) Adhesion
- ) Aggregation
- ) Plug Formation
- ) Fibrin Formation
- ) Clot Retraction
Name the 5 step of the Platelet Function cascade ?
- ) Circulating platelets; endothelial damage occurs.
- ) Platelet Adhesion
- ) Platelet Aggregation
- ) Plug Formation
- ) Fibrin Formation
- ) Clot retraction
Platelets may become activated by any of several physiologic or pathologic acivators released or exposed a the site of injury. Name 8 of theses activators ?
- Adenosine Diphosphate (ADP)
- Arginine Vasopressin (AVP or ADH)
- Platelet Activating Factor ( PAF)
Platelet activators are counterbalanced by the presence of several inhibitors of activation which include what ?
- Flowing Blood
- Endothelial products
- Prostacyclin (PgI2) &
- Nitric Oxide
Injury (or disease) of the vessel endothelium exposes a number of adhesive subendothelial proteins which promotes formation of a platelet plug which adheres to the exposed sub-endothelium. Name the 2 main components ?
- Glycoprotein (GP Ib)
* Von Willebrand factor
During Aggregation, platelets adhere to each other to form a plug. Adherent platelets release dense bodies and alpha granules, name the 3 main components ?
- GP IIB
- GP IIIa
Recite the sequence of the Prostaglandin pathway?
Membrane Phospholipid ↓ Arachidonic Acid ↓ Prostaglandin Endoperoxides ↓ ↓ PG12 Thromboxane A2
Membrane Phospholipid is the substrate for what ?
Arachidonic Acid is the substrate for what ?
Prostaglandin Endoperoxides are the substrates for what ?
What INHIBITS platelet aggregation ?
What INDUCES platelet aggregation ?
2 Primary Hemostatic Disorders?
- Inherited = in the young
* Acquired = Most problematic
Without the Prostaglandin Pathway, the platelets . . . .
Will not work
4 Inherited Platelet Disorders
- von Willebrand Disease
- Glanzmann’s Thrombasthenia
- Bernard Soulier Disease
- Deficient Release Reaction
What is the most common platelet disorder?
von Willebrand Disease
What disorder lacks GP IIB
GP IIIa ?
How would you treat this ?
Bernard Soulier Disease
lacks what ?
Protein 1b which is necessary for adhesion.
4 Acquired Platelet Disorders ?
Chronic leukemia’s that effects the platelets that the body produces
Aspirin has a blocking effect on what portion of the prostaglandin pathway ?
- Screening test for primary hemostasis
- Not a good predictor of surgical bleeding risk
- Very technique-dependent
Platelet Function Analyzer (PFA)
is the modern “In vitro bleeding time”
How can we look at individual affects of different activators on platelets? What test should we order?
Platelet Aggregation Studies
Platelet Function Analysis via a bleeding time study would provide what information ?
Platelet Function Screen via a Platelet Function Analyzer (PFA) study would provide what information ?
- Platelet number
- Platelet function
With the (PFA 100 Principle) Citrated whole blood is aspirated through a capillary towards a membrane that is coated with what agonists that activate platelets?
Agonists in combination with high shear stresses create an environment where . . .
adhesion, activation, and aggregation can be evaluated.
During a PFA interpretation what are the normal values for collagen/Epinephrine ?
94 - 194 sec
Abnormal values for Collagen/Epinephrine would indicate what possible platelet disorders?
- Intrinsic platelet defects,
- vWD, or
- platelet inhibiting agents
Abnormal values for Collagen/ADP would indicate what possible platelet disorders?
intrinsic platelet defect or vWF
During a PFA interpretation what are the normal values for Collagen/ADP ?
71 - 118 sec
Cascade system activated by substances released at the time of injury
Coagulation Factor X III =
Fibrin Stabilizing Factor
Factor XIII deficiency causes hemophilia A
During Intrinsic pathway, XII + Surface contact =
Extrinsic pathway begins with the release of an intracellular lipoprotein, tissue thromboblastin (FACTOR III) by vascular injury outside the vessel. In the presence of Calcium, tissue thromboplastin activates what ?
The thromboblastin factor VIIa complex then activates factor X from the common pathway & factor IX from the intrinsic pathway.
In the Common Pathway,
Xa + (Va, phospholipids, & Calcium) =
Prothrombin activator complex which activates prothrombin (Factor II) to Thrombin
In the Common Pathway, Thrombin + Fibrinogen (I) =
Long strands of Fibrin
In the Common Pathway, Thrombin also activates what other factors?
Factor XIII (fibrin stabilizing factor)
Factor XIIIa &
forming an insoluble meshwork that is incorporated into the platelet plug.