38
Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

  • View
    250

  • Download
    5

Embed Size (px)

Citation preview

Page 1: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Hemostasis/Thrombosis I

Normal Hemostasis/Thrombosis; Assessment of Clotting System

Page 2: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

HEMOSTASIS & THROMBOSIS

• Platelets• Coagulation Cascade• Regulation of Coagulation

Page 3: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

CIRCULATORY SYSTEM• Low volume, high pressure system• Efficient for nutrient delivery to tissues• Prone to leakage 2º to endothelial

surface damage• Small volume loss large decrease in

nutrient delivery• Minimal extravasation in critical areas

irreparable damage/death of organism

Page 4: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

HEMOSTASISPrimary vs. Secondary vs. Tertiary

• Primary Hemostasis– Platelet Plug Formation– Dependent on normal platelet number & function– Initial Manifestation of Clot Formation

• Secondary Hemostasis– Activation of Clotting Cascade Deposition &

Stabilization of Fibrin

• Tertiary Hemostasis– Dissolution of Fibrin Clot– Dependent on Plasminogen Activation

Page 5: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

HEMOSTATIC DISORDERSSuspicions

• Spontaneous bleeding• Prolonged or excessive bleeding after

procedures or trauma• Simultaneous bleeding from multiple

sites

Page 6: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

HEMOSTATIC DEFECTS

BleedingProblem

PlateletDisorder

CoagulationAbnormality

Petechiae + -

BleedingSites

MucousMembrane

Deep Tissue

Time ofonset ofbleeding

Immediate Delayed

Ecchymoses/Hematomas

+ +

Page 7: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

HEMOSTATIC ABNORMALITIES"Screening Tests" (History)

• Dental Extractions• Prior Surgery/Biopsy• Easy bruising• Heavy menses• Deliveries• Blood transfusion

Page 8: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

PLATELETS• Anucleate cellular fragments; multiple granules,

multiple organelles• Synthesis controlled by IL-6, IL-3, IL-11, &

thrombopoietin• Circulate as inactive, non-binding concave discs• On stimulation, undergo major shape change• Develop receptors for clotting factors• Develop ability to bind to each other &

subendothelium

Page 9: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System
Page 10: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System
Page 11: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

PLATELET ACTIVATION

vWFRestingPlatelets Platelet

Adhesion

Page 12: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Initial Thrombin Formation

VIIa-TF

X Xa

II IIaIIa

TR

Page 13: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

PLATELET ACTIVATION

PlateletActivation

VIIa-TF

X Xa

II IIa

Page 14: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Platelet Release

TxA2, ADP, Serotonin, Fibrinogen, Thrombospondin

VIIa-TF

X Xa

II IIa

Page 15: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

PLATELET PLUG FORMATION

Page 16: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System
Page 17: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System
Page 18: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADEGeneral Features

• Zymogens converted to enzymes by limited proteolysis

• Complex formation requiring calcium,phospholipid surface, cofactors

• Thrombin converts fibrinogen to fibrin monomer

• Fibrin monomer crosslinked to fibrin• Forms "glue" for platelet plug

Page 19: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADE

Page 20: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

THROMBIN

• Serine protease• Cleaves fibrinogen to fibrin• Activates V to Va, VIII to VIIIa• Activates platelets-cleaves thrombin

receptor• Activates XIII to XIIIa• In presence of thrombomodulin

activates Protein C to APC

Page 21: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADE

Page 22: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Platelet Release

TxA2, ADP, Serotonin, Fibrinogen, Thrombospondin

VIIa-TF

X Xa

II IIa

VIIa-TF

IX IXa

VIII VIIIa

V Va

Page 23: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Tenase/Prothrombinase complex assembly

VIIIa R

VIIIa/IXa

X Xa

Va/Xa

Va R

II IIa

Page 24: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

FIBRIN FORMATIONA

B

A

B

F XIIIa

T

Page 25: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

VITAMIN K DEPENDENT CARBOXYLASE

• Post-translational modification• Factors II, VII, IX, X; proteins C & S• Converts 1st 7-12 glutamic acids to

γ-carboxyglutamic acid• Confers calcium binding and lipid binding on

these proteins• Without vitamin K, secrete des-

γ-carboxyglutamic acid containing proteins(inactive in coagulation)

Page 26: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

γ -CARBOXYGLUTAMIC ACID

γ-carboxy Glu

COO-COO-

COO-

CH

CH2

CHNH3+

COO-

COO-

CH2

CH2

CHNH3+

Glu

O2, CO2

Vit KCarboxylase

Page 27: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

PLATELET FUNCTION STUDIES

• Bleeding Time• Platelet Count• Platelet Aggregation Studies

Page 28: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

BLEEDING TIME vs. PLATELET COUNT

0

50

100

150

200

250

300

350

400

3.5 4 4.5 5 5.5 7 9 12 15 25 30

Minutes

Pla

tele

t co

un

t (x

100

0)

Page 29: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADE

Page 30: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Clotting Tests• Recalcification times• Blood collected in sodium citrate, a weak

calcium chelator• Amount designed to drop calcium

concentration to < 1 mM• At that level, blood won’t clot

spontaneously• RBC’s & platelets centrifuged off, leaving

plasma (unclotted liquid portion of blood)

Page 31: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

Prothrombin Time

• Mixture of: – 50% patient’s platelet poor plasma– 25% Mixture of Tissue Factor &

phospholipid species– 25% Calcium chloride (to bring final

calcium concentration to c. 3-5 mM)– Time to clot formation measured

Page 32: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADE

Va/Xa/PLVa/Xa/PL

VIIa/TFVIIa/TF

TF FVII

FG

F

FVIIaCa+2

V VaT

Ca+2FXFXa Ca+2

Ca+2PT

TCommon Pathway

Middle Components

EXTRINSIC PATHWAY

ProthrombinTime (PT)

Page 33: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

aPTT (activated partial thromboplastin time)

• 50% patient’s platelet-poor plasma• 25% mixture of phospholipid & surface

active agent (Celite, Kaolin)• 25% Calcium Chloride to bring calcium

concentration to 3-5 mM• Time to clot formation measured

Page 34: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADE

Va/Xa/PLVa/Xa/PL

VIIIa/IXa/PLVIIIa/IXa/PL

FXIIFXIIa

FG

F

HMWKFXI

FXIa

Ca+2FIXFIXa Ca+2

VIII VIIIaT

V VaT

Ca+2FXFXa Ca+2

Ca+2PT

TCommon Pathway

Middle Components

Surface Active Components

INTRINSIC PATHWAY

aPTT

Page 35: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADEContact Phase

F XII

F XIIa

HMWK

F XI

F XIa

Prekallikrein

Kallikrein

Page 36: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADEIntermediate Phase

IXa/VIIIa/PL

VIIa/TF/PL

F IX

F IXa

Ca+2

Ca+2

Ca+2

XIa

F VII/TF

F VIIa/TF

Ca+2

VIII VIIIa +T

F X

F Xa

Tenase Complex

Page 37: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

COAGULATION CASCADECommon Pathway

IXa/VIIIa/PL VIIa/TF/PL

F Xa

F XF X

V Va + Xa/Va/PL

PT

TFibrinogen

Fibrin monomer

Prothrombinase ComplexCa+2

Ca+2 Ca+2

Page 38: Hemostasis/Thrombosis I Normal Hemostasis/Thrombosis; Assessment of Clotting System

CLOTTING ASSAYSSpecific factors/Inhibitors

• Deficiency states of every clotting protein described

• 50% of any clotting factor will yield normal PT and/or aPTT

• Mix 1/2 patient plasma with 1/2 factor deficient plasma; then perform PT and/or aPTT

• Factor deficient plasma with missing factor will prolonged clotting time; all others WNL

• If more than one clotting assay prolonged, implies inhibitor to clotting protein