Hemostasis and Coagulation
Miklós Molnár
Definition of HEMOSTASIS
The arrest of bleeding by repair of vessel
wall
Maintaining a balance
Coagulation
Fibrinolysis
Hypocoagulation: excessive bleeding
(inherited or acquired)
Hypercoagulation (thrombosis) inadequate
activation of the fibrinolytic system
Systems Involved in Hemostasis
Vascular system
Injured vessel initiates vasoconstriction
Platelet System
Injured vessel exposes collagen that initiates
platelet aggregation and help form plug
Coagulation System
protein factors of intrinsic and extrinsic
pathways produce a permanent fibrin plug
HEMOSTASIS
Primary 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
Primary Hemostasis
vasoconstriction (vascular system)
platelet exposure to subendothelial
connective tissue of blood vessels
Platelet release of ADP, ATP, Thromboxane
A2 (promotes vasoconstriction)
Platelet aggregation, phospholipid provides
site for fibrin formation
Platelet Origin & Development
Endomitosis
Multiple mitotic division of DNA without
cytoplasmic division
Largest cell in the BM low power
Stem cell to mature platelet = 5 days
Each megakaryocyte can shed 500-4000
platelets
Cytoplasm breaks apart along demarcation
membranes
Megakaryocyte
Platelets forming from cytoplasm
Normal platelets and one giant platelet
Platelet Structure
Three zones
Peripheral 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, glycogen
mitochondria, lysosomes
Glycocalyx
Glycoproteins
Ib (GPIb)
Receptor site for vWF
IIb, IIIa (GPIIb/IIIa)
Complex becomes receptor site for
fibrinogen
Granular content
Dense granules
ATP
ADP
Calcium
Magnesium
Serotonin
epinephrine
Granular content
(Alpha granules)
Hemostatic
proteins
Fibrinogen
Factor V
vWF
Plasminogen
Plasminogen
activator inhibitor
(PAI-1)
α2-antiplasmin
Nonhemostatic
proteins
β-thromboglobulin,
Platelet factor 4
Platelet derived
growth factor
(PDGF)
Albumin
fibronectin,
Formation of primary hemostatic plug
Platelets converted from inactive to active
state
Adhesion to collagen
Triggers platelet activation
Tromboxane A2 is synthesized from arachidonic acid
and stimulates secretion
Aggregation of platelets to each other
prostacyclin (PGI2) inhibits platelet aggregation
Secretion (discharge of granule contents)
VON WILLEBRAND FACTOR
Large Adhesive Glycoprotein
Polypeptide chain: 220,000 MW
Base structure: Dimer; Can have as many as
20 linked dimers
Multimers linked by disulfide bridges
Synthesized in endothelial cells &
megakaryocytes
Constitutive & stimulated secretion
Large multimers stored in Weibel-Palade
bodies
Functions:
1) Stabilizes Factor VIII
2) Essential for platelet adhesion
Stable adhesion
Platelet activation/
Platelet aggregation
Rolling
Blood Flow
VWF
VWF
Platelet
adhesion
VWF
collagen
collagen
VWF
VWF
collagen
collagen
VWF
Inactive
Active
Secondary hemostasis
Intrinsic Pathway
All components required for initiating this
pathway are circulating in the blood
triggered by contact with collagen or glass
Extrinsic Pathway
Initiated by the release of tissue
thromboplastin and calcium from damaged
tissue
Common Pathway
Leads to clot formation including the platelet
plug and fibrin produced
Coagulation Proteins
Zymogens
enzyme precursors II, VII, IX, X, XI, XII,
Prekallkrein
When activated become serine proteases
Cofactors
Nonenzymatic V, VIII, HMWK, Tissue
factor(thromboplastin)
Kinin factors prekallikrein, kallikrein,
HMWK
Roles include coag activation as well as
fibrinolytic activation
Coag factors (by group)
Fibrinogen group: I,V,VIII,XIII
most labile, are consumed in coagulation, found
on platelets
Prothrombin group: II,VII,IX,X
Vitamin K dependent, may be affected by
coumarin,diet, antibiotics
Contact group: XI,XII,HMWK,
Prekallikrein
initiate intrinsic path and fibrinolysis
VIIa
+
Tissue factor
pathway inhibitor
X
Positive
feedback
Xa
Tissue Factor (TF)
Tissue Damage
Vessel wall
Cell particles
II
IIa
(prothrombin)
(thrombin)
Initial Tissue Factor Pathway Activation of Hemostasis
IIa
Thrombin
Pro-coagulant
effects
XI
XIa
VIII
VIIIa
V
Fibrinogen
Va
Fibrin
XIa
IX
Precursor
IXa
Enzyme
Reaction on Activated Platelets
FVIIIa/Ca2+/Phospholipid
X
Xa
FVa/Ca2+/Phospholipid
II
Fibrinogen
IIa
Fibrin
FIBRINOLYTIC SYSTEM
Definition: temporary fibrin clot
systematically and gradually dissolved as
the vessel heals
Key components
Plasminogen (inactive form)
Plasminogen activators
Plasmin
Fibrin
Fibrin Degradation Products (FDP)
Inhibitors of plasminogen activators and
plasmin
Activators of Fibrinolysis
Intrinsic activators
Factor XIIa, XIa, kallikrein
Extrinsic activators
Tissue type plasminogen activator (t-PA)
Urokinase type plasminogen acitvator
(u-PA)
Exogenous activators
Streptokinase (derived from beta strep)
XII
XIIa
XI
Protein S
XIa
IX
IXa
Protein S
Protein C
VIIIa+Ca+Pl
X
Xa
Va+Ca+Pl
TF / VIIa
TFPI
II
Fibrinogen
IIa/Thrombomodulin
interaction
IIa
Fibrin
Fibrinolysis
VIIIa
Va
Protein S
IIa
Thrombin
Anti-coagulant
effects
Activated
Protein C
Protein C
IIa
thrombomodulin
Protein C Anticoagulant Pathway
Coagulation 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 II
serine protease inhibitors (serpins)
Deficiency of inhibitors cause increased
risk of thrombosis
Inhibitors of Fibrinolysis
Plasminogen Activator Inhibitors (PAI)
α2 –antiplasmin
α2 -macroglobulin
Bleeding disorders
Disorders of Hemostasis
Vascular disorders
Scurvy, easy bruising, Henoch-Schönlein purpura.
Platelet disorders
Quantitative - Thrombocytopenia
Qualitative - Platelet function disorders –
Glanzmans
Coagulation disorders
Congenital - Haemophilia (A, B), Von-Willebrands
Acquired - Vitamin-K deficiency, Liver disease
Mixed/Consumption: DIC
Tests of Hemostasis:
Screening tests:
Bleeding.T  10m. Platelet & BV function
Prothrombin.T  Extrinsic, aPTT  Instrinsic
Thrombin.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- Coag
Skin / Mucosal Bleeds – PLT
wound / surgical bleeding –
Immediate - PLT
Delayed - Coagulation
Platelet
Coagulation
Petechiae, Purpura Hematoma, Joint bl.
Vascular disorders:
Petechiae, purpura, ecchymoses
senile purpura
vitamin C deficiency (scurvy)
Connective tissue disorders
Infections – Meningococcus
Henoch-Schonlein Purpura-Immu
Senile Purpura
Petechiae in
Vasculitis
(Rocky Mountain Spotted Fever)
Henoch-Schölein purpura
Immune disorder
Children
Follows infection
Petechiae 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 bleeding
Petechiae, Purpura, Ecchymosis.
Spontaneous bleeding after trauma
CNS bleeding (severe  plt)
Prolonged bleeding time (BT)
BLEEDING TIME vs. PLATELET COUNT
Platelet count (x 1000)
400
350
300
250
200
150
100
50
0
3,5
4
4,5
5
5,5
7
Minutes
9
12
15
25
30
REDUCED PLATELET NUMBER:
THROMBOCYTOPENIA
Normal platelet count
140-400
Increased bleeding time
<100
Spontaneous bleeding
<20
PLATELET FUNCTION DEFECTS
Prolonged Bleeding Time
Congenital
Drugs
Alcohol
Uremia
Hyperglobulinemias
Fibrin/fibrinogen split products
Thrombocythemia
Cardiac Surgery
PLATELET FUNCTION DEFECTS
Platelet Adhesion
Bernard Soulier Disease
Abnormal GPIb-IX Complex
Receptor for von Willebrand factor
Only adhesion mediator @ high shear stress
Tested by ability to aggregate platelets in
presence of ristocetin
Von Willebrand disease
Reduced or dysfunctional von Willebrand
factor
Von-Willebrand Disease:
Coagulation + PLT disorder:
Congenital disorder
Deficiency of vWF molecule
Part of FVIII,
Mediates platelet adhesion
Prolonged Bleeding time
Low Factor VIII & long aPTT
Mucocutaneous bleeding
Von-Willebrand Disease
vWF: F-VIII & PLT function.
Defective Platelet Adhesion
Skin Bleeding
Prolonged Bleeding time.
Low Factor VIII levels.
Prevalence: 0.8–2% (probable
underestimate)
PLATELET FUNCTION DEFECTS
Platelet Release Defects - Congenital
-storage pool disease
Failure to form dense granules
syndrome)
(Hermansky-Pudlak
Do not release ADP, serotonin, calcium on
activation
Fail to recruit platelets for aggregation
Gray platelet syndrome
Failure of packaging of α-granules
Do not release protein mediators of platelet
aggregation
Decreased platelet aggregation
Mild bleeding disorder
PLATELET FUNCTION DEFECTS
Aggregation-Congenital
Glanzmann's thrombasthenia
Autosomal recessive
Lack of fibrinogen receptor, GP IIb/IIIa
Platelets cannot aggregate in response
to usual stimuli
Bleeding sometimes severe
Platelet Aggregation Curves
PLATELET FUNCTION DEFECTS
Acquired - Drug Induced
Alcohol
Prostaglandin Synthetase Inhibitors
Aspirin
Non-Steroidal Antiinflammatory Drugs
Phenylbutazone
ADP receptor inhibitors
Clopidogrel
Ticlopidine
Beta-lactam antibiotics
Heparin
THROMBOCYTOPENIA
Decreased production
Decreased megakaryocytes
Normal platelet life span
Good response to platelet transfusion
Neoplastic Causes
Leukemias
Aplastic Anemia
Metastatic Carcinoma
Drugs
Radiotherapy
Primary Marrow Disorders
Megaloblastic Anemias
Myelodysplastic syndromes
Myeloproliferative diseases
Some congenital syndromes
THROMBOCYTOPENIA
Increased Destruction
Shortened platelet life span
Increased megakaryocytes
Macroplatelets
Poor response to platelet transfusion
THROMBOCYTOPENIA
Increased 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 platelets
Platelets removed by macrophages
Antibodies can act on marrow
No good diagnostic test
Treatment - Inhibit macrophage clearance
Corticosteroids
High dose gamma globulin
Splenectomy
HIV-ASSOCIATED
THROMBOCYTOPENIA
Early
Immune mediated
Often in absence of AIDS
Remainder of marrow WNL
Treatment - Antiretroviral therapy
Late
Usually marrow infiltration
Often pancytopenia
Often associated infection or neoplasm
Poorly responsive to all treatments
Coagulation disorders:
Deficiencies of Clotting factors
Onset - delayed after trauma
Deep bleeding
Into joints - Hemarthroses
Into deep tissues – Hematoma
large skin bleed – Ecchymoses
Coagulation Disorders
Laboratory findings:
Normal bleeding time & Platelet count
Prolonged 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 (Hemophilia A)
X-linked disorder (affects 1º males)
Prevalence is 1:5,000 males
Most common - severe bleeding
Spontaneous hematomas
Abnormal aPTT – Intrinsic path.
Diagnosis - factor VIII assay
Treatment - factor VIII concentrate
Cryoprecipitate (less desirable)
Factor IX Deficiency
Christmas disease (Hemophilia B)
X-linked recessive disorder
Prevalence is 1:30,000 males
Indistinguishable from classic hemophilia
(F VIII)
Requires evaluation of factor VIII and
IX activity levels to diagnose
Treatment - factor IX concentrate
Cryoprecipitate if factor IX unavailable
FACTOR XI DEFICENCY
(Hemophilia C)
Inherited form transmitted as an
autosomal recessive trait.
Prevalence is 1:100,000
Increased prevalence in Ashkenazi Jewish
population (in Israel, estimated at 8%)
A clinically mild bleeding problem
Prolongs only the PTT
Most often associated with liver disease
Secondary Hemostatic Disorders
Vitamin K deficiency
Neonates - decreased intestinal
flora and dietary intake
Oral anticoagulants (coumadin)
Fat malabsorption syndromes
Required for factors II, VII, IX,
- Prolonged PT and aPTT
Combined Primary and Secondary
Hemostatic Disorders
Disseminated Intravascular Coagulation (DIC)
Major pathologic processes obstetric complications, neoplasms,
infection (sepsis), major trauma
Primary - platelet consumption
( bleeding time,  platelets)
Secondary - factor consumption
( PT, aPTT)
Combined Primary and Secondary
Hemostatic Disorders
Severe 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
Petechiae
Sites
Time
Ecchymoses
/Hematomas
Platelet
Yes
Coagulation
No
Skin &
Mucosa
Immediate
Deep Tissue
Yes
Yes
Delayed