General Principles of Hemostasis · • Measures extrinsic pathway Prothrombin Time. TF VII IX VIII...
Transcript of General Principles of Hemostasis · • Measures extrinsic pathway Prothrombin Time. TF VII IX VIII...
Hemostasis is a balancing act!
pro-clotting anti-clotting
plugs up holes in blood vessels
keeps clotting under control
Platelets form a plug.• Proteins are exposed• Platelets adhese• Granules release contents• Platelets aggregate• Phospholipids are exposed
Pro-Clotting
Fibrin seals up plug.• Tissue factor is exposed• Cascade begins• Cascade makes fibrin• Fibrin solidifies plug
Pro-Clotting
Final common pathway
clotfibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXIXIIaXII
thrombin
Coagulation Cascade
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
Where does tissue factor come from?
• �Hidden� cells exposed during injury
• Microparticles floating in blood
• Endothelial cells and monocytes (during inflammation)
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
clot
fibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
busydistractingsinful
SINtrinsic
clot
clotfibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
simplerivetingsexy
SEXtrinsic
clotfibrinfibrinogen
thrombinprothrombin
XaVa
TFVIIa VII
exposed TF
X
IXa
VIIIaVIII
V
IX
Intrinsic Extrinsic
XIaXI
thrombin
proteinC
ATIII
TFPI
Why?• Evaluate platelet response to vascular injury• Some platelet disorders have a long bleeding time How?• Inflate blood pressure cuff• Make incision• Time how long it takes to stop bleedingCareful!• Lots of things affect the test!• Some consider the test unreliable.
Bleeding Time
• Draw blood into citrate tube
• Spin tube, decant plasma
• Add reagents to plasma
• Watch for formation of fibrin
Coagulation Lab Tests
TFVIIIX
VIII
fibrin
clot
thrombin
XV
Intrinsic Extrinsic
The PT is increased in:• ¯ VII, X, V, II, I• Coumadin• Heparin• DIC
• To assess liver function
• To monitor Coumadin therapy
• To diagnose DIC*
• To assess pre-op status
When should you order an INR?
* Disseminated intravascular coagulation
• Plasma + phospholipid
• Measures intrinsic pathway
• APTT = same thing
Partial Thromboplastin Time
TFVIIIX
VIII
fibrin
clot
thrombin
XV
Intrinsic Extrinsic
The PTT is increased in:• hemophilia A• hemophilia B• DIC• heparin
• To investigate a history of abnormal bleeding
• To monitor heparin therapy
• To diagnose DIC
• To assess pre-op status
When should you order a PTT?