hemostasis principles

1Revised: mmvi

Principles of HemostasisPrinciples of HemostasisPrinciples of Hemostasis

Marlies Ledford-Kraemer, MBA, BS, MT(ASCP)SH

www.CLOT-ED.com 2

Topics for Discussion

IntroductionVirchow’s Triad

Primary Hemostasis

Secondary Hemostasis

Physiologic Coagulation

Laboratory Coagulation

Fibrinolysis

www.CLOT-ED.com 3

VirchowVirchow’’ss TriadTriad

www.CLOT-ED.com 4

Virchow’s Triad

Changes in blood coagulabilityPlatelets, Coagulation Factors & Inhibitors, Fibrinolysis

Changes in blood flowRheology in vessels

Changes in vessel wallEndothelial changes due to inflammation or atherogenesis

www.CLOT-ED.com 5

Vessel Wall

http://www.alegent.com/122711.cfm

Tunica intima

Endothelium - inner most layer of cells that separate the remainder of the vessel from the lumenBasement membrane – thin layer of spongy connective tissue that secretes elastic collagen

Tunica intermedia

Surrounds the tunica intimaSmooth muscle – layer of smooth muscle cells that are under involuntary control and can dilate or constrictConnective tissue – produces collagen fibers whose elasticity is reduced by hypertension

Tunica adventitia

Surrounds the tunica mediaConnective tissues – produce elastic and non-elastic collagen fibersPrevents ballooning of vessel with high systolic blood pressureAneurysm – weaknesses in the tunica adventitia

www.CLOT-ED.com 6

Rheology

Science of the deformation and flow of matterBlood is a fluidized suspension of elastic cells that demonstrates both a viscous and elastic effect– Elastic effect makes blood a non-Newtonian fluid (plasma is a Newtonian fluid)– Blood has a yield stress that depends on hematocrit and fibrinogen concentration

Region 2As shear rate increases:

Cells are disaggregatingApplied forces (yield stress) are forcing cells to orient and deformBlood viscosity decreases

Region 1In this range of shear rates:

Cells are in large aggregates (rouleauxformation)As shear rate increases, size of aggregates diminishViscoelasticity is strongly influenced by aggregation tendency of RBCs Region 3

With increasing stress:Cells deformWith normal deformability, cells will form layers that slide on layers of plasma and align in the direction of flow

Adapted from : http://www.vilastic.com/tech10.html

www.CLOT-ED.com 7

At Vessel Center: Greatest Velocity & Least Shear Rate

At Wall Surface: Greatest Shear Rate & Least Velocity

Shear Flow

Laminae (Arrow Length = Velocity)

Platelet

Platelet Flowing Blood

Endothelial Cells

Endothelial Cells

Shear StressPressure- induced Force Between 2 Laminae

Shear & Vessel Wall

www.CLOT-ED.com 8

Hemostasis

Process by which blood is maintained in a fluid state and confined to the circulatory systemGoal is to stop bleeding and to do so only at the site of injuryComponents– Platelets

• Involved in Primary Hemostasis

– Coagulation system• Involved in Secondary Hemostasis

– Fibrinolytic system– Inflammatory processes– Wound healing processes

Platelet / fibrin mesh

www.CLOT-ED.com 9

Primary HemostasisPrimary Hemostasis

www.CLOT-ED.com 10

Primary HemostasisFirst physiological response to vascular injury, which is mediated by platelets, in order to arrest bleedingMechanism– Activation of platelets via stimulators such as thrombin– Adhesion of platelets to subendothelium via interaction

between GPIb and von Willebrand Factor (VWF)– Release of platelet granule products in order to recruit

more platelets to the injured site– Aggregation of platelets via interaction between

GPIIb/IIIa (αIIbβ3) and fibrinogen to form the initial plugTriggers secondary hemostasis (coagulation proteins)Affected by medications, platelet function status, and vessel wall status

www.CLOT-ED.com 11

PlateletsDisk-shaped cell fragments produced in the bone marrow by megakaryocytesLife span ~ 10 daysGlycoprotein Ib (GPIb) is involved in adhesionGlycoprotein IIb/IIIa(GPIIb/IIIa) is the primary receptor for fibrinogen (aggregation phase)Provide procoagulantsurface on which coagulation proteins can interact GPIb

Densegranules

Alphagranules

Coagulation proteins

GPIIb/IIIa

www.CLOT-ED.com 12

Platelet Adhesion

Subendothelial extracellular matrix

COLCOL

COL

VWF

VWF

COLCOL

VWFVWF

Endothelium VWF Injury site collagen exposed

Platelet

GPIb

www.CLOT-ED.com 13

Platelet Aggregation

Subendothelial extracellular matrix

COLCOL

COL

VWF

VWF

COLCOL

VWFVWF

Fibrinogen

VWF

GPIbActivated Platelet

(Granule contents released)

GPIIb/IIIa

www.CLOT-ED.com 14

Tests for Primary HemostasisBleeding Time– Assesses all components of Virchow’s triad– in vivo test – performed directly on patient– Has fallen into disrepute and replaced by instruments that perform “in

vitro” bleeding times

Platelet Aggregation studies– Measure ability of platelets to aggregate, in vitro, when subjected to

various stimulators (agonists)– Predominantly assesses function of platelet glycoprotein IIb/IIIa

receptor

Von Willebrand Factor (VWF) assays– Measure amount and function of VWF, a protein that works with

platelets so that they adhere to site of injury– Assesses function of VWF ligand in its interaction with platelet

glycoprotein Ib receptor

www.CLOT-ED.com 15

Platelet Appearance / Function

Resting platelets

Activated platelets

Electron Micrographs Aggregation Tracings

Normal platelet function

Aspirin-like defect

www.CLOT-ED.com 16

Secondary HemostasisSecondary Hemostasis

www.CLOT-ED.com 17

Secondary Hemostasis

Process of blood coagulationMechanism– Coagulation proteins work in

concert to generate thrombin– Thrombin converts fibrinogen to

fibrin– Fibrin consolidates the platelet plug

made in primary hemostasis such that a thrombus (secondary hemostatic plug) is formed

Prevents further blood loss from the injury site

Credit: Weisel JW. University of Pennsylvannia

www.CLOT-ED.com 18

Factor XII (FXII) activated FXII (FXIIa)Factor XI (FXI) activated FXI (FXIa)Factor X (FX) activated FX (FXa)Factor IX (FIX) activated FIX (FIXa)Factor VIII (FVIII) activated FVIII (FVIIIa)Factor VII (FVII) activated FVII (FVIIa)Factor V (FV) activated FV (FVa)

Coagulation Factors

Factor II (prothrombin) is converted to thrombin (FIIa)

Factor I (fibrinogen) is converted to fibrin

www.CLOT-ED.com 19

“in vivo” v “in vitro” Coagulation

Physiologic (“in vivo”) coagulation is dependent upon the tissue factor pathway– Goal is to form a thrombus

Laboratory (“in vitro”) coagulation is dependent upon the contact system– Classical “waterfall” or cascade concept

• Step-by-step biochemical reactions in which an inactive proenzymeis converted to a reactive enzyme which, in turn, converts another proenzyme to its active form

– Amplification process (very minute amounts of Factor XII yield large amounts of thrombin)

– Goal is to form a clot

www.CLOT-ED.com 20

Waterfall Scheme of Coagulation

After Macfarlane RG. Nature 1964;202:498-9

FXI FXIa

Fibrinogen Fibrin

FXII FXIIaFXIIa

FVIIIa

FIX FIXaCa++ PL

FX FXaCa++ PL

FVaFII ThrombinCa++ PL

TF

FX

FVIIFVIIa

TF = Tissue Factor

Ca+ += Calcium ion

PL = Phospholipid

www.CLOT-ED.com 21

Physiologic CoagulationPhysiologic Coagulation

Thrombus FormationThrombus Formation

www.CLOT-ED.com 22

Initiation PhaseMonroe DM, et al. ATVB 2006;26:41-8

“Extrinsic Pathway”

www.CLOT-ED.com 23

Amplification PhaseMonroe DM, et al. ATVB 2006;26:41-8

www.CLOT-ED.com 24

Propagation PhaseMonroe DM, et al. ATVB 2006;26:41-8

“Intrinsic Pathway”

www.CLOT-ED.com 25

Tissue Factor complexed with FVIIa initiates coagulation at site of injury

Small amounts of thrombin are generated that activate platelets

Coagulation factors form complexes on platelet surfaces

Very large amounts of thrombin are formed to convert fibrinogen to fibrin

Fibrin reinforces platelet plug (primary hemostasis) and hemostasis is achieved

Recapping Secondary Hemostasis

www.CLOT-ED.com 26

Laboratory CoagulationLaboratory Coagulation

Clot FormationClot Formation

www.CLOT-ED.com 27

First the SpecimenBlood is collected into a tube that contains sodium citrate, an anticoagulantBlood fluidity is maintained because sodium citrate binds calcium ions, which are critical to the coagulation processTube is centrifuged in order to separate plasma from buffy coat (white blood cells & platelets) and red blood cells

Plasma is used for testing– PLASMA contains

FIBRINOGEN– Serum does not contain

Fibrinogen

Plasma is “platelet poor”since platelets remain in buffy coat

Plasma

Buffy Coat

Red Cells

www.CLOT-ED.com 28

Coagulation in the Laboratory

Intrinsic Pathway

XIIXI

IXVIII

Fibrin Clot

Extrinsic Pathway

VIITissue Factor

X

V

Fibrinogen

IIPathwayCommon

APTTIntrinsic

+Common

PTExtrinsic

+Common

www.CLOT-ED.com 29

Routine Coagulation Assays

Prothrombin Time (PT)Activated Partial Thromboplastin Time (APTT)Quantitative Fibrinogen (FIB)Thrombin Time (TT)Assays for specific coagulation factors– Factors assessed by a PT-based test system: FVII, FV, FX,

and FII– Factors assessed by an APTT-based test system: FXII,

FXI, FIX, and FVIII

www.CLOT-ED.com 30

Prothrombin Time (PT)

0.1 ml Thromboplastin + Ca++

0.1 ml Plasma

Incubate at 37 oC for ~3 minutes

Time for clot formation~ 12 seconds

PT Reagent CompositionThromboplastin− Tissue Factor (recombinant/human or animal brain)− Lipid (source of phospholipid since platelets were removed from plasma)− CaCl2 – used to reintroduce calcium ions that were chelated by sodium citrate

Historically referred to as “complete” since both phospholipid and apoproteinmake up the reagent

Credit: PNAS; Collet JP and Weisel JW. Un Pennsylvannia

www.CLOT-ED.com 31

Causes for Prolonged PTDeficiencies or abnormalities in:– FVII (Extrinsic Pathway)– FV, FX, FII (prothrombin), and FI (fibrinogen)

• Both PT and APTT will be prolonged

Vitamin K antagonists– PT sensitive to reductions in three of four vitamin K-dependent

procoagulant proteins: FVII, FX, and FII• FIX measured by APTT

– Pharmacologic anticoagulants that modify vitamin K-dependent proteins such that they do not bind calcium thereby reducing blood coagulability

Liver disease– Site for synthesis of vitamin K-dependent proteins– Site for clearance of coumarins (warfarin) and coagulation proteins

www.CLOT-ED.com 32

Biochemistry: Vit K-Dep Proteins

binding to phospholipidsurfaces and generation of membrane bound macromolecular complexes

Addition of an extra carboxyl group to glutamate (Glu) residues at their amine termini gives rise to a novel amino acid called gamma-carboxyglutamate (Gla)– Presence of Gla enables proteins to undergo a calcium-

dependent conformational change that allows for their

www.CLOT-ED.com 33

Vitamin K Antagonists (AVK)DICUMAROL: 3,3’-methylenebis (4-hydroxycoumarin)– Isolated by Karl Link (University of Wisconsin-1939) as the anti-

vitamin K agent responsible for hemorrhagic disorder in cattle – Coumarin derivatives

• Bishydroxycoumarin (Dicumarol)• Warfarin (Coumadin®)

– Analog #42 of many coumarins synthesized by Dr Link and named by him as WARFarin for the Wisconsin Alumni Research Foundation and coumARIN

Require monitoring because:– Vitamin K-dependent proteins have different half-lives– Differences in drug absorption and clearance– Levels affected by concomitant medications, comorbid conditions,

changes in diet, patient compliance– PT (thromboplastin) reagents vary in their reaction to clotting defects

produced by AVK (warfarin)

www.CLOT-ED.com 34

Warfarin SodiumOral anticoagulant of choice in North AmericaPharmacologic properties more favorable than Dicumarol– Warfarin is 5-10x more potent

Racemic mixture (~1:1) of R & S isomers– S isomer is 5x more potent than R isomer

• Hepatic microsomal enzyme cytochrome P450 2C9 is responsible for the oxidative metabolism of S isomer

Bioavailability– Absorbed from gastrointestinal tract– Maximal blood concentrations reached in 90 minutes– Half-life (T½) is 36-42 hours– At therapeutic concentrations, 99% of warfarin is bound to albumin

and 1% is free and can bind to its receptor on hepatic cellsAnticoagulant effects are reversed by administration of vitamin K or biologic products that contain vitamin K-dependent proteins

www.CLOT-ED.com 35

Warfarin Mode of Action

Des-CarboxyProthrombin (“Glu”)

Prothrombin(“Gla”)

WARFARIN

NADHNAD+Regeneration of active form is sensitive to

warfarin

CO2

Vitamin K2, 3 epoxide

(inactive form K1O)

Vitamin Khydroquinone

(active form K1H2)Vitamin K

γ-Carboxylase

O2

H2O

epoxide reductase(VKOR)

www.CLOT-ED.com 36

International Normalized Ratio

“Normalizes” the PT by mathematically considering differences in PT reagents (thromboplastins)Only to be used to monitor long term anticoagulant effects for patients stabilized on oral anticoagulant therapy– Prevent recurrence of thrombosis caused by under

anticoagulation– Prevent hemorrhagic complications caused by over

anticoagulation

INR =

ISI

Mean Normal PT

Patient PT

www.CLOT-ED.com 37

Activated Partial Thromboplastin Time

APTT Reagent CompositionActivator to convert FXII to FXIIaPhospholipid (replaces “in vivo” platelet surface on which coagulation reactions occur)CaCl2 – used to reintroduce calcium ions that were chelated by sodium citrateReferred to as “partial thromboplastin” since no Tissue Factor is used− Two-stage assay (activation and re-calcification)

0.1 ml Activator

0.1 ml Plasma



0.1 ml CaCl2

www.CLOT-ED.com 38

Intended Use for APTT

Screening test– Intrinsic (and severe common pathway) factor deficiencies

Laboratory monitoring– Unfractionated heparin– Other antithrombotic agents (Direct Thrombin Inhibitors)

Laboratory detection of the Lupus Anticoagulant

www.CLOT-ED.com 39

Causes for Prolonged APTT

Most common causes– Heparin (contamination from lines or therapeutic)– Lupus Anticoagulant

Other causes– Deficiencies of coagulation factors

• FVIII (Hemophilia A or Von Willebrand Disease), FIX, FXI, FXII

– Liver disease (site of production for most coagulation factors)

– Consumption of coagulation factors as seen in Disseminated Intravascular Coagulation (DIC)

www.CLOT-ED.com 40

HeparinHeparin is a heterogeneous group of straight-chain anionic mucopolysaccharides (glycosaminoglycans)– Molecular weights range from 5 – 40 kiloDaltons– Composed of alternating D-glucosamine residues linked 1 → 4

to either L-iduronic acid or D-glucuronic acidHeparin is highly acidic therefore binds to positively charged amino acids such as arginine & lysine– Pentasaccharide sequence

• Comprisies ~30% of heparin• Binds to antithrombin (AT)• Accelerates AT inhibition of

activated factors XII, XI, IX, X, and II (thrombin) thus serving as an anticoagulant

Pharmaceutical heparins are extracted from pig intestinal mucosa (source of mast cells)

www.CLOT-ED.com 41

Heparin and Antithrombin

www.CLOT-ED.com 42

APTT Monitoring of Heparin

Assumes antithrombotic (anti-IIa) effect parallels anticoagulant effectLimitations– Pre-treatment APTT of patient

• Baseline APTT of patient prolonged due to Lupus Anticoagulant• Baseline APTT of patient sample below or at low end of reference

interval due to high levels of FVIII (apparent “heparin resistance”)

– APTT reagents vary in sensitivity to heparin• Laboratories must determine responsiveness of their APTT reagent

to unfractionated heparin• Determine APTT therapeutic interval (seconds) for reagent used to

monitor heparin therapy

www.CLOT-ED.com 43

Direct Thrombin InhibitorsHirudin [Lepirudin (rDNA)–trade name: Refludan®]– Approved in USA, Canada, and EU for Heparin Induced

Thrombocytopenia (HIT) complicated by thrombosis– Target APTT is 1.5-2.5 x patient baseline APTT– In absence of severe thrombosis, some experts recommend a target

APTT of 1.5-2.0 x patient baseline APTT and monitor every 4 hours

Argatroban [non-US trade name: Novastan]– Approved for HIT with or without thrombosis and also for

anticoagulation during percutaneous coronary intervention (PCI) in patients with, or at risk for, HIT

– Target APTT 1.5-3.0 x patient baseline APTT (maximum 100 seconds)

Hirulog [Bivalirudin-trade name: Angiomax™]– Undergoing evaluation for use as an anticoagulant for “on-pump” and

“off-pump” cardiac surgery in patients with HIT– Target APTT is 1.5-2.5 x patient baseline APTT

www.CLOT-ED.com 44

“Recap”ping the PT and APTT

PT and APTT are screening assays to determine if a patient, when challenged, has a potential to bleed– If warfarin or heparin are not present in sample, then:

• Prolonged PT and normal APTT = deficiency of FVII• Normal PT and prolonged APTT = deficiencies in any of the intrinsic

pathway factors (FVIII, FIX, FXI, or FXII)• Prolongation of both PT and APTT = deficiencies of factors common

to both pathways (FX, FV, FII, or fibrinogen)

PT, via the INR, is used to monitor oral anticoagulant therapy (warfarin)APTT is used to monitor heparin anticoagulant therapyAPTT is affected by inhibitors such as Lupus Anticoagulant

www.CLOT-ED.com 45

Tests for FibrinogenQuantitative Fibrinogen

Measures the amount of fibrinogen present in plasmaLow levels, termed hypofibrinogenemia, can be inherited but generally are due to acquired causes such as DIC, liver disease, or fibrinolytic therapyHigh levels are seen in inflammatory states since fibrinogen is an acute phase reactant

Thrombin Time (TT)Assesses the functionality of fibrinogen in plasmaTT clotting time prolonged– HEPARIN– Direct thrombin inhibitors– Hypofibrinogenemia– Dysfibrinogenemia– Elevated fibrin split products

0.2 ml Diluted ThrombinIncubate at 37 oC for ~2 minutes


0.2 ml Plasma

0.2 ml Diluted ThrombinIncubate at 37 oC for ~2 minutes


0.2 ml Plasma

www.CLOT-ED.com 46

Quantitative Fibrinogen

1

100

10 100 10001155810 230 460

5.1

9.5

18.3

35.0Cl

ottin

g Ti

me-

Seco

nds

mg/dl Fibrinogen

1281

8.0 Patient

1

100

10 100 10001155810 230 460

5.1

9.5

18.3

35.0Cl

ottin

g Ti

me-

Seco

nds

mg/dl Fibrinogen

11

100

10 100 10001155810 230 460

5.1

9.5

18.3

35.0Cl

ottin

g Ti

me-

Seco

nds

mg/dl Fibrinogen

1281

8.0 Patient

Patient clotting time in seconds is read against the reference curve− Patient clotting time of 8.0

seconds equates to 281 mg/dl fibrinogen in example at right

Fibrinogen concentration is inversely proportional to clotting time

Calibrator plasma is serially diluted (1:5, 1:10, 1:20, and 1:40) to establish a reference curve (see graph below)Patient plasma is diluted 10 fold (1:10) in buffer

0.1 ml Thrombin

0.2 ml Diluted Plasma


Time for clot formation~ 5-14 seconds

www.CLOT-ED.com 47

Coagulation: A Balancing Act

Generate ThrombinGenerate Thrombin

Inhibit Thrombin Formation

Inhibit Thrombin Formation

www.CLOT-ED.com 48

Inhibitors

Naturally occurring inhibitors– Protein C (activated) and Protein S

• Inhibit coagulation cofactors FVIIIa and FVa

– Antithrombin• Inhibits FXIa, FIXa, FXa, FVIIa/TF, and thrombin (IIa)

Pathologic inhibitors – Acquired or autoimmune antibodies to specific

coagulation factorsPharmacologic inhibitors– Heparin and Low Molecular Weight Heparin– Warfarin– Direct Thrombin Inhibitors

www.CLOT-ED.com 49

FibrinolysisFibrinolysis

www.CLOT-ED.com 50

Hemostasis: A Delicate Balance

Form a Thrombus

Form a Thrombus

Generates Thrombin

Generates Plasmin

Dissolve a ThrombusDissolve a Thrombus

www.CLOT-ED.com 51

Fibrinolytic System

TMThrombin

TAFIa

TAFI

FXIII

FIBRINFIBRINFibrinogen

‡

Thrombin

PC APCTM

Fibrin(ogen) DegradationProducts

Plasmin

PlasminogentPA

PAI-1

Antiplasmin

‡

www.CLOT-ED.com 52

Breakdown of Fibrin(ogen)

FibrinClot

DDEEDD

Fragment XFragment X

DD YY

Thrombin

FibrinogenFPA & BFPA & B

Fibrin MonomerFibrin Monomer

Fibrin PolymerFibrin Polymer

DDEEDDDDEEDD

FXIII FXIIIa

Fibrinogen FPBFPB

PLASMIN

D-dimer DD DDEEDDDDEEDD

www.CLOT-ED.com 53

Fibrinolytic Agents

All currently available thrombolytic agents are plasminogen activators (PA)– Convert patient plasminogen to plasmin which then acts

on fibrin within a thrombus– Additionally can breakdown fibrinogen (fibrinogenolysis)

• Commonly referred to as the lytic state (systemic lysis)• Therapeutic doses of PA overwhelm PAI-1 and α2-antiplasmin

Beneficial effect is reduction of thrombus size (thrombolysis)Negative effect is that hemostatic plugs are also lysedMost commonly used agents are: Streptokinase (SK), Alteplase (tPA), Reteplase, and Tenecteplase (TNK-tPA)

www.CLOT-ED.com 54

SummariesSummaries

www.CLOT-ED.com 55

Time Frame for Hemostasis

PrimaryHemostasis

• Vessel constriction occurs immediately

• Platelet adhesion occurs in seconds

• Platelet aggregation takes minutes

PrimaryHemostasis

• Vessel constriction occurs immediately

• Platelet adhesion occurs in seconds

• Platelet aggregation takes minutes

Platelets

SecondaryHemostasis

• Activation of coagulation factors occurs in seconds

• Fibrin forms in minutes

SecondaryHemostasis

• Activation of coagulation factors occurs in seconds

• Fibrin forms in minutes

Coagulation Factors

Fibrinolysis

• Activation of fibrinolyticproteins happens immediately

• Dissolving the thrombus requires hours

Fibrinolysis

• Activation of fibrinolyticproteins happens immediately

• Dissolving the thrombus requires hours

Fibrinolytic Proteins

www.CLOT-ED.com 56

Bleeding: Balance is Disrupted

Presence of Inhibitors*•Pharmacologic (warfarin, heparin)•Allo or Auto-antibodies to Factors

www.CLOT-ED.com 57

Thrombosis: Balance is Disrupted

Inhibitors*• Activated Protein C• Protein S• Antithrombin

www.CLOT-ED.com 58

Conclusion

Primary hemostasis, a platelet-dependent process, forms hemostatic plugs when a vessel is injuredSecondary hemostasis, a coagulation factor-dependent process, begins with Tissue Factor exposure– Small amounts of thrombin are generated via FXa

formation by the TF:FVIIa complex (“Extrinsic Pathway”)– Sustained thrombin generation depends on FXa

formation via FIXa and FVIIIa-mediated complexes on an activated platelet surface

– Amount of thrombin generated dictates bleeding or thrombotic risk

The clinical history is the best “test” for hemostasis

www.CLOT-ED.com 59

ReferencesAnsell J, et al. The pharmacology and management of the vitamin K antagonists: The Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004;126:204S-233S.Clinical and Laboratory Standards Institute (CLSI). One-stage Prothrombin Time (PT) test and Activated Partial Thromboplastin Time (APTT) test; Approved Guideline H47-A, 1996.Crowther MA, et al. Practical aspects of anticoagulant therapy (Chapter 89). In: Colman RW, ed. Hemostasis and Thrombosis, 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2001.Fairweather RB, et al. College of American Pathologists Conference XXXI on Laboratory Monitoring of Anticoagulant Therapy: Laboratory monitoring of oral anticoagulant therapy. Arch Pathol Lab Med 1998;122(9):768-81.Greaves M, Preston FE. Approach to the bleeding patient (Chapter 48). In: Colman RW, ed. Hemostasis and Thrombosis, 4th ed. Philadelphia: Lippincott Williams & Wilkins, 2001.Hirsh J, Raschke R. Heparin and low-molecular-weight heparin: The Seventh ACCP Conference on Antithromboticand Thrombolytic Therapy. Chest 2004;126:188S-203S.Konkle BA. Clinical approach to the bleeding patient (Chapter 77). In: Colman RW, ed. Hemostasis and Thrombosis, 5th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.Link KP. The discovery of Dicumarol and its sequels. Circulation 1959;19(1):97-107.Olson JD, et al. College of American Pathologists Conference XXXI on Laboratory Monitoring of Anticoagulant Therapy: Laboratory monitoring of unfractionated heparin therapy. Arch Pathol Lab Med 1998;122(9):782-98.Physicians’ Desk Reference, 60th ed. Montvale: Thomson PDR, 2006.Poller L. Prothrombin Time (Chapter 6) and Activated Partial Thromboplastin Time (Chapter 5). In: Jespersen J, ed. Laboratory Techniques in Thrombosis-A Manual, 2nd ed. Dordrecht: Kluwer Academic Publishers, 2000.Tran HAM, Ginsberg JS. Anticoagulant therapy for major arterial and venous thromboembolism (Chapter 116). In: Colman RW, ed. Hemostasis and Thrombosis, 5th ed. Philadelphia: Lippincott Williams & Wilkins, 2006.van den Besselaar, AMHP, Gralnick HR, Lewis SM, Editors. Thromboplastin Calibration and Oral Anticoagulant Control. Dordrecht: Martinus Nijhoff Publishers, 1984.

hemostasis principles

Documents