Hemostasis Flashcards
The stages of hemostasis?
Primary
Secondary
Fibrinolysis
What is primary hemostasis?
Formation of the platelet plug
What is secondary hemostasis?
Coagulation
When the actual clot forms
What is fibrinolysis?
Clot is dissolved
What is the vessel itself’s initial response to injury?
Vasospasm
What stimulates the vasospasm of the injured vessel to occur?
Disrupted endothelium
What stage includes formation of the platelet plug?
Primary
What initiates formation of the platelet plug?
Injury to vessel exposes endothelial collagen
What coagulation factor is required for adhesion of platelets?
Von Wilebrand
vW
What factor(s) activate platelets for the platelet plug?
Thrombin and tissue factor
What is meant by platelet activation?
Platelets change shape
What prostaglandin promotes platelet aggregation?
Thromboxane
What substances are also included in the platelet plug?
Fibrinogen and thrombin
Aggregation of platelets triggers further?
Attraction of more platelets
Platelet activation
What kind of bleeding/injury do platelet plugs control?
Minute vessel breaks that occur constantly
-full clot not required
Platelet counts under what allow spontaneous bleeding to occur?
< 20,000
Intercerebral hemorrhage can occur from just a platelet count below?
< 20,000
Thrombocytopenia means what? And what can you see with this as evidence of someone unable to form platelet plugs?
Low platelet count
Petechia
Production of thromboxane requires what?
Cyclooxygenase (COX)
What inhibits the production of the prostaglandin thromboxane?
Cox inhibitors interferes with the enzyme cyclooxygenase, which means it interferes with the production of thromboxane
COX inhibitors interfere with what part of hemostasis?
Function of the platelets
- platelet aggregation
- formation of a platelet plug
What COX inhibitor has temporary interference on hemostasis?
NSAIDs
How long do NSAIDs interfere with platelet function?
1-2 days
What cox inhibitor has permanent interference on platelet function?
Aspirin
Why is ASA interference considered permanent?
It lasts the life of a platelet
What is the life of a platelet?
8-12 days
-1-2 weeks
How long does ASA interfere with platelet function?
1-2 weeks
What lab tests will tell platelet function, NOT count?
Bleeding time
What bleeding time may indicate bleeding risk?
Over 7-8 minutes
What platelet count constitutes thrombocytopenia?
< 100,000
What platelet count constitutes surgical bleeding risk?
< 50,000
What platelet count constitutes spontaneous bleeding?
< 20,000
What are the 4 A’s of platelet plug?
Activation
Adhesion
Aggregation
Attraction
What changes the platelet plug into a clot?
Fibrin
What is the inactive form of fibrin?
Fibrinogen
What factor converts fibrinogen into fibrin?
Thrombin
What is the inactive form of thrombin?
Prothrombin
What factor converts prothrombin into thrombin?
Factor X
What constitutes the chain of events that occur from factor X > fibrin formation?
The common pathway
The formation of fibrin requires what substances?
Fibrinogen
Calcium
Thrombin
The formation of thrombin requires what substances?
Prothrombin
Calcium
Factor X
What (old) 2 pathways were described to get to factor X?
Extrinsic and Intrinsic pathway
What factors are involved in the extrinsic pathway and what lab test would show abnormalities?
III
VII
PT
What factors are involved in the intrinsic pathway and what lab test would show abnormalities?
VIII IX XI XII PTT
What has replaced the intrinsic/extrinsic pathways?
The cell based theory
-tissue factor theory
What factor does the cell based theory say triggers coagulation?
Factor III
What are the many names for factor III?
Tissue factor
Thromboplastin
Tissue thromboplastin
What are the phases of cell based theory?
Initiation
Amplification
Propagation
Describe initiation phase
Triggered by vessel injury to endothelial surface exposing tissue factor
Tissue factor and factor VII activate factor X
How much thrombin is created due to initiation phase
Only a small amount
Describe the amplification phase
XXX
How much thrombin is created from the activation stage?
Thrombin generation is gaining momentum
Describe the propagation phase
XXXX