hemostasis and coagulation miklós molnár. definition of hemostasis the arrest of bleeding by...
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Hemostasis and Coagulation
Miklós Molnár
Definition of HEMOSTASISDefinition of HEMOSTASIS
The arrest of bleeding by repair of vessel wallMaintaining a balance
CoagulationFibrinolysis
Hypocoagulation: excessive bleeding (inherited or acquired)Hypercoagulation (thrombosis) inadequate activation of the fibrinolytic system
Systems Involved in Hemostasis
Vascular systemInjured vessel initiates vasoconstriction
Platelet SystemInjured vessel exposes collagen that initiates platelet aggregation and help form plug
Coagulation Systemprotein factors of intrinsic and extrinsic pathways produce a permanent fibrin plug
HEMOSTASISPrimary vs. Secondary vs. TertiaryPrimary vs. Secondary vs. TertiaryHEMOSTASISPrimary vs. Secondary vs. TertiaryPrimary vs. Secondary vs. Tertiary
Primary HemostasisPlatelet Plug FormationDependent on normal platelet number & functionInitial Manifestation of Clot Formation
Secondary HemostasisActivation of Clotting Cascade Deposition & Stabilization of Fibrin
Tertiary HemostasisDissolution of Fibrin ClotDependent on Plasminogen Activation
vasoconstriction (vascular system)platelet exposure to subendothelial connective tissue of blood vesselsPlatelet release of ADP, ATP, Thromboxane A2 (promotes vasoconstriction)Platelet aggregation, phospholipid provides site for fibrin formation
Primary Hemostasis
Platelet Origin & Development
Endomitosis Multiple mitotic division of DNA without cytoplasmic division
Largest cell in the BM low powerStem cell to mature platelet = 5 daysEach megakaryocyte can shed 500-4000 plateletsCytoplasm breaks apart along demarcation membranes
Megakaryocyte
Platelets forming from cytoplasm
Normal platelets and one giant platelet
Platelet StructurePlatelet Structure
Three zonesPeripheral zone (adhesion & aggregation)
glycocalyx, plasma membrane
Sol-gel zone (structure & support)microfilaments, thrombosthenin, open canalicular system, dense tubular system
Organelle zone (Secretion & storage)granules: alpha, dense, glycogenmitochondria, lysosomes
Glycocalyx
GlycoproteinsIb (GPIb)
Receptor site for vWF
IIb, IIIa (GPIIb/IIIa)Complex becomes receptor site for fibrinogen
Granular content
Dense granulesATPADPCalciumMagnesiumSerotoninepinephrine
Granular content (Alpha granules)
Hemostatic proteins
FibrinogenFactor VvWFPlasminogenPlasminogen activator inhibitor (PAI-1)α2-antiplasmin
Nonhemostatic proteins
β-thromboglobulin,Platelet factor 4Platelet derived growth factor (PDGF)Albuminfibronectin,
Formation of primary hemostatic plug
Platelets converted from inactive to active state
Adhesion to collagenTriggers platelet activationTromboxane A2 is synthesized from arachidonic acid and stimulates secretion
Aggregation of platelets to each otherprostacyclin (PGI2) inhibits platelet aggregation
Secretion (discharge of granule contents)
VON WILLEBRAND FACTORLarge Adhesive GlycoproteinPolypeptide chain: 220,000 MWBase structure: Dimer; Can have as many as 20 linked dimersMultimers linked by disulfide bridgesSynthesized in endothelial cells & megakaryocytesConstitutive & stimulated secretionLarge multimers stored in Weibel-Palade bodiesFunctions:1) Stabilizes Factor VIII2) Essential for platelet adhesion
VWF
VWF
VWF
VWF VWF VWF
collagencollagen
collagen
collagen
Blood Flow
Platelet adhesion
PlateletRolling
Stable adhesion
Platelet activation/ aggregation
Inactive Active
Secondary hemostasis
Intrinsic PathwayAll components required for initiating this pathway are circulating in the bloodtriggered by contact with collagen or glass
Extrinsic PathwayInitiated by the release of tissue thromboplastin and calcium from damaged tissue
Common PathwayLeads to clot formation including the platelet plug and fibrin produced
Coagulation Proteins
Zymogens enzyme precursors II, VII, IX, X, XI, XII, PrekallkreinWhen activated become serine proteases
CofactorsNonenzymatic V, VIII, HMWK, Tissue factor(thromboplastin)
Kinin factors prekallikrein, kallikrein, HMWK
Roles include coag activation as well as fibrinolytic activation
Coag factors (by group)Coag factors (by group)
Fibrinogen group: I,V,VIII,XIIImost labile, are consumed in coagulation, found on platelets
Prothrombin group: II,VII,IX,XVitamin K dependent, may be affected by coumarin,diet, antibiotics
Contact group: XI,XII,HMWK, Prekallikrein
initiate intrinsic path and fibrinolysis
Tissue DamageVessel wall
Cell particles
Tissue Factor (TF)
VIIa+ X Xa
II(prothrombin)
IIa(thrombin)
Initial Tissue Factor Pathway Activation of Hemostasis
Tissue factorpathway inhibitor
Positive feedback
IIaThrombin
XI XIa
VIII VIIIa
V Va
Pro-coagulant effects
Fibrinogen Fibrin
XIa
IX IXa
X Xa
II IIa
Fibrinogen Fibrin
FVIIIa/Ca2+/Phospholipid
FVa/Ca2+/Phospholipid
Precursor Enzyme
Reaction on Activated Platelets
FIBRINOLYTIC SYSTEMFIBRINOLYTIC SYSTEMFIBRINOLYTIC SYSTEMFIBRINOLYTIC SYSTEM
Definition: temporary fibrin clot systematically and gradually dissolved as the vessel healsKey components
Plasminogen (inactive form)Plasminogen activatorsPlasminFibrinFibrin Degradation Products (FDP)Inhibitors of plasminogen activators and plasmin
Activators of Fibrinolysis
Intrinsic activatorsFactor XIIa, XIa, kallikrein
Extrinsic activatorsTissue type plasminogen activator (t-PA)Urokinase type plasminogen acitvator
(u-PA)
Exogenous activatorsStreptokinase (derived from beta strep)
XII XIIa
XI XIa
IX IXa
X Xa
TF / VIIa
II IIa
Fibrinogen Fibrin
VIIIa+Ca+Pl
Va+Ca+Pl IIa/Thrombomodulin
interactionTFPI
Protein CProtein S
Protein S
Fibrinolysis
IIaThrombin
Anti-coagulant effects
thrombomodulin
IIa
VIIIa Va
Protein CActivatedProtein C
Protein S
Protein C Anticoagulant Pathway
Coagulation Regulatory MechanismsCoagulation Regulatory Mechanisms
Naturally Occurring Anticoagulants rapidly interact with components of coag cascade to avoid unabated clot formation
Protein C (PC) and Protein S (PS)deficiencies may be congenital or acquired
Antithrombin (AT) and Heparin Cofactor IIserine protease inhibitors (serpins)
Deficiency of inhibitors cause increased risk of thrombosis
Inhibitors of Fibrinolysis
Plasminogen Activator Inhibitors (PAI)α2 –antiplasmin
α2 -macroglobulin
Bleeding Bleeding ddisordersisorders
Disorders of Hemostasis
Vascular disorders Scurvy, easy bruising, Henoch-Schönlein purpura.
Platelet disordersQuantitative - ThrombocytopeniaQualitative - Platelet function disorders – Glanzmans
Coagulation disordersCongenital - Haemophilia (A, B), Von-WillebrandsAcquired - Vitamin-K deficiency, Liver disease
Mixed/Consumption: DIC
Tests of Hemostasis:
Screening tests: Bleeding.T 10m. Platelet & BV function Prothrombin.T Extrinsic, aPTT InstrinsicThrombin.T common path. (DIC)
Specific tests:Factor assays – hemophilia.Tests of thrombosis – TT, FDP, DDA, Platelet function studies:
Adhesion, Aggregation, Release tests.
Bone Marrow study
Bleeding: Clinical Features
Local-vs- General, spontaneous…Hematoma / Joint Bleeds- CoagSkin / Mucosal Bleeds – PLTwound / surgical bleeding – Immediate - PLT Delayed - Coagulation
PlateletCoagulation
Petechiae, Purpura Hematoma, Joint bl.
Vascular disorders:
Petechiae, purpura, ecchymosessenile purpuravitamin C deficiency (scurvy)Connective tissue disordersInfections – MeningococcusHenoch-Schonlein Purpura-Immu
Senile PurpuraSenile Purpura
Petechiae in Petechiae in VasculitisVasculitis
(Rocky Mountain Spotted (Rocky Mountain Spotted Fever)Fever)
Henoch-Schölein purpura
Immune disorderChildrenFollows infectionPetechiae with edema and itching.
Henoch-Schönlein purpura
20y Male, fever, painful symmetric polyarthritis for a day. During the next two days, edema and palpable purpura developed.
Platelet Disorders - Features:
Mucocutaneous bleedingPetechiae, Purpura, Ecchymosis.Spontaneous bleeding after traumaCNS bleeding (severe plt)Prolonged bleeding time (BT)
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 cou
nt (x
100
0)
REDUCED PLATELET NUMBER:
THROMBOCYTOPENIA
Normal platelet count 140-400
Increased bleeding time <100
Spontaneous bleeding Spontaneous bleeding <20 <20
PLATELET FUNCTION DEFECTSProlonged Bleeding TimeProlonged Bleeding Time
CongenitalDrugsAlcoholUremiaHyperglobulinemiasFibrin/fibrinogen split productsThrombocythemiaCardiac Surgery
PLATELET FUNCTION DEFECTSPlatelet AdhesionPlatelet Adhesion
Bernard Soulier DiseaseAbnormal GPIb-IX ComplexReceptor for von Willebrand factorOnly adhesion mediator @ high shear stressTested by ability to aggregate platelets in presence of ristocetin
Von Willebrand diseaseReduced or dysfunctional von Willebrand factor
Von-Willebrand Disease:
Coagulation + PLT disorder:Congenital disorderDeficiency of vWF molecule Part of FVIII, Mediates platelet adhesionProlonged Bleeding timeLow Factor VIII & long aPTTMucocutaneous bleeding
Von-Willebrand Von-Willebrand DiseaseDiseasevWF: F-VIII & PLT function.Defective Platelet AdhesionSkin Bleeding Prolonged Bleeding time.Low Factor VIII levels.Prevalence: 0.8–2% (probable underestimate)
PLATELET FUNCTION DEFECTSPlatelet Release Defects - CongenitalPlatelet Release Defects - Congenital-storage pool disease
Failure to form dense granules (Hermansky-Pudlak syndrome)
Do not release ADP, serotonin, calcium on activationFail to recruit platelets for aggregation
Gray platelet syndromeFailure of packaging of α-granulesDo not release protein mediators of platelet aggregation
Decreased platelet aggregationMild bleeding disorder
PLATELET FUNCTION DEFECTSAggregation-CongenitalAggregation-Congenital
Glanzmann's thrombastheniaAutosomal recessiveLack of fibrinogen receptor, GP IIb/IIIa
Platelets cannot aggregate in responseto usual stimuliBleeding sometimes severe
Platelet Aggregation CurvesPlatelet Aggregation Curves
PLATELET FUNCTION DEFECTSAcquired - Drug InducedAcquired - Drug Induced
AlcoholProstaglandin Synthetase Inhibitors
AspirinNon-Steroidal Antiinflammatory DrugsPhenylbutazone
ADP receptor inhibitorsClopidogrelTiclopidine
Beta-lactam antibioticsHeparin
THROMBOCYTOPENIATHROMBOCYTOPENIADecreased productionDecreased productionDecreased megakaryocytes
Normal platelet life spanGood response to platelet transfusion
Neoplastic CausesLeukemiasAplastic AnemiaMetastatic CarcinomaDrugsRadiotherapy
Primary Marrow DisordersMegaloblastic AnemiasMyelodysplastic syndromesMyeloproliferative diseasesSome congenital syndromes
THROMBOCYTOPENIATHROMBOCYTOPENIAIncreased DestructionIncreased Destruction
Shortened platelet life span Increased megakaryocytesMacroplateletsPoor response to platelet transfusion
THROMBOCYTOPENIAIncreased Destruction - CausesIncreased Destruction - Causes
Immune ITP Lymphoma Lupus/rheumatic diseases Drugs
Consumption Disseminated intravascular coagulation Thrombotic thrombocytopenic purpura Hemolytic/uremic syndrome
Septicemia
IDIOPATHIC THROMBOCYTOPENIA PURPURA
(ITP)
Acute - children (post infection)Chronic - adults ( females,20-40 yrs)IgG autoantibodies bound to plateletsPlatelets removed by macrophagesAntibodies can act on marrowNo good diagnostic testTreatment - Inhibit macrophage clearance
CorticosteroidsHigh dose gamma globulinSplenectomy
HIV-ASSOCIATED THROMBOCYTOPENIA
Early Immune mediatedOften in absence of AIDSRemainder of marrow WNLTreatment - Antiretroviral therapy
LateUsually marrow infiltrationOften pancytopeniaOften associated infection or neoplasmPoorly responsive to all treatments
Coagulation disorders:
Deficiencies of Clotting factorsOnset - delayed after traumaDeep bleeding
Into joints - HemarthrosesHemarthroses Into deep tissues – HematomaHematoma large skin bleed – EcchymosesEcchymoses
Coagulation DisordersLaboratory findings:Laboratory findings:
Normal bleeding time & Platelet countProlonged prothrombin time (PT)
deficiencies of II, V, VII, X
Prolonged time (aPTT)all factors except VII, XIII
Mixing studies - normal plasma corrects PT or aPTT
Factor VIII Deficiency Classic hemophilia (Classic hemophilia (HHemophilia A)emophilia A)
X-linked disorder (affects 1º males)Prevalence is 1:5,000 malesMost common - severe bleedingSpontaneous hematomasAbnormal aPTT – Intrinsic path.Diagnosis - factor VIII assayTreatment - factor VIII concentrateCryoprecipitate (less desirable)
Factor IX DeficiencyChristmas disease (Hemophilia B)Christmas disease (Hemophilia B)
X-linked recessive disorderPrevalence is 1:30,000 males Indistinguishable from classic hemophilia (F VIII)Requires evaluation of factor VIII and IX activity levels to diagnoseTreatment - factor IX concentrateCryoprecipitate if factor IX unavailable
FACTOR XI DEFICENCY ((HHemophilia C)emophilia C)
Inherited form transmitted as an autosomal recessive trait.Prevalence is 1:100,000Increased prevalence in Ashkenazi Jewish population (in Israel, estimated at 8%) A clinically mild bleeding problemProlongs only the PTTMost often associated with liver disease
Secondary Hemostatic Disorders
Vitamin K deficiencyVitamin K deficiency
Neonates - decreased intestinal flora and dietary intakeOral anticoagulants (coumadin)Fat malabsorption syndromesRequired for factors II, VII, IX, - Prolonged PT and aPTT
Combined Primary and Secondary Hemostatic
Disorders Disseminated Intravascular Coagulation Disseminated Intravascular Coagulation
(DIC)(DIC) Major pathologic processes -obstetric complications, neoplasms, infection (sepsis), major traumaPrimary - platelet consumption
( bleeding time, platelets)Secondary - factor consumption
( PT, aPTT)
Combined Primary and Secondary Hemostatic
DisordersSevere Liver DiseaseSevere Liver Disease
Primary - dysfunctional platelets and/or thrombocytopenia (BT)Secondary - decrease in all coagulation factors except vWF (PT, aPTT)Vitamin K will promote synthesis of factors II, VII, IX, X
Summary
Symptom Platelet Coagulation Petechiae Yes No
Sites Skin & Mucosa
Deep Tissue
Time Immediate Delayed
Ecchymoses/Hematomas
Yes Yes