Hemostasis and Thrombosis

1
Hemostasis and Thrombosis

• Chapter 23

2
Principle of Hemostasis

• Circulatory hemostasis is achieved by
• Hemorrhage (Bleeding)
• Thrombosis (Clotting)
• Process of arresting of bleeding which includes 4
  components
• 1. Vascular system
• 2. Platelets
• 3. Coagulation factors
• Fibrinolysis
• 3 less important factors include complement,
  kinins and serine protease inhibitors

3
Process of hemostasis at site of injury

• Blood vessel spasm
• Formation of a platelet plug
• Contact between blood vessel , plts and
  coagulation proteins
• Fibrinolytic process to reestablish vascular
  integrity.

4
Vascular structure consist of 3 tunics

• Tunica Intima- next to flow of blood
• Tunica media- thickest smooth
• Tunica Adventitia
• All vessels contain these linings, Veins are
  larger-more irregular lumens than arteries, they
  have relative thin walled and weaker middle coat.

5
Blood Vasculature

• Arteries-Thickest walls and the largest
• Arterioles-microscopic continuation of arteries
  to form metarterioles
• Capillaries
• Capillaries, arterioles and venules are the major
  vessels of the microcirculation, function to link
  between arterial and venous circulation.

6
Vascular role in Vasoconstriction

• Vessels are injured-start an immediate self
  healing process
• Vasoconstriction-decrease blood flow
• Endothelium- influences movement of fluid and
  inflammation. (3 types of endothelin)

7
Endothelin

• Endothelin 1- produced in the endothelial cells
  and vascular smooth muscle cells. Stimulated by
  hypoxia, ischemia or stress- short lived
• Endothelin 2 produced in the kidney and
  intestine, small amount in myocardium, placenta
  and uterus.
• Endothelin 3- circulates in the plasma, found in
  the brain and functions in proliferation and
  development of neurons and astrocytes.
• 2 Receptors for endothelin (A and B) mediate
  vasoconstriction action

8
Function of Endothelium

• Contains connective tissues that regulate the
  permeability of vessel walls and provides
  principle stimulus to thrombosis
• Plasminogen activator-rapid lysis of fibrin clot.
• Prostacyclin- inhibits platelet aggregation and
  adhesion
• Collegan initiates contact activation of Factor
  XII
• Coagulation process typically proceeds without
  notice but can be altered by various substances,
  injuries, illness etc.

9
Alteration include

• Enhanced permeability to plasma lipoproteins
• Hyper adhesiveness
• Functional imbalances
• Collectively known as endothelial dysfunction and
  are important in initiation, progression and
  clinical complications of vascular and
  inflammatory diseases.

10
Endothelial dysfunction

• Immunoregulatory substances (IL-1 and TNF)
• Viral infections
• Bacterial toxins
• Cholesterol and oxidatively modified lipoprotein

11
Disruption activates hemostasis components

• Rapid Vasoconstriction
• Platelet adhesion
• Coagulation (Intrinsic and extrinsic systems)
• Fibrinolysis
• (Table 23.2, pg 342)

12
Maintenance of Vascular integrity

• Requires 3 essential factors (circulating)
• Platelets
• Adrenocorticosteroid
• Ascorbic acid
• Depending on the size of the vessel, and the
  presence of the factors influences the stability
  of the vessels.

13
Megakaryocytic Cells

• 2nd critical component of hemostasis
• Produced in the BM through phases
• Begins with pogenitor
• BFU-M
• CFU-M
• Both committed to megakaryocyte lineage.
• The next stage is the development of a small
  mononuclear marrow cell-not recognizable-transitio
  nal cells and represent 5 of the marrow
  megakaryocytes.

14

• Final stage is the development of the
  megakaryocyte-large and lobulated.
• Largest cell of the marrow (160µm)
• NC is high 112
• The platelet formation begins with the initial
  appearance of a pink color in the basophilic
  cytoplasm of the megakaryocyte and increased
  granularity.

15
Mature Platelet

• 2-4µm, Younger plts larger than older ones.
• No nucleus, cytoplasm light blue, red-purple
  granules.
• Very sensitive cells, respond to minimal
  stimulation. Stronger stimulation causes
  stronger response within the circulation.

16
Structure

• Fundamental function
• Glycocalyx
• Cytoplasmic membrane
• Microfilaments and microtubules
• Granules (Alpha, dense and lysosomes)
• Contractile proteins

17
Platelet kinetic, life span and values

• Average megakaryocyte produces 1000-2000
• Maturation period in marrow 5 days
• Two third of total plts. in circulation, other
  third in platelet pool in the spleen. normal
  value 250-450,000
• Life span 9/- 1 day

18
Function in hemostasis

• Need to present in normal number, quantity and
  function.
• Involved in platelet adhesion and aggregation
  during hemostasis.
• Damage occurs to a vessel and the following
  occurs
• Plt. adhesion to the site
• Shape change
• Platelet aggregation
• Secretion
• All the events are structural or functional
  change

19
Platelets activated by

• ADP (nucleotide)
• Lipid (thromboxane A2, platelet activating
  factor)
• Collagen (structural protein)
• Thrombin (proteolytic enzyme)
• One of the main activities of platelet function
  is the formation of the platelet plug through
  platelet adhesion.

20
Platelet adhesion

• Spread psuedopods along cell surface
• Clump
• Adhesion of plts to collagen occurs within 1-2
  min of damage
• Release of epinephrine and serotonin promotes
  vasoconstriction.
• ADP released enhances adhesion
• Release of granular content (alpha, dense and
  lysosomes)
• After platelet activated will express functional
  glycoprotein IIb/IIIa receptors (intergrin alpha
  IIb beta3) for circulating ligand proteins
  (fibrinogen)

21
Glycoprotein IIb/IIIa

• Promote platelet cohesion by forming fibrinogen
  bridge between platelets.
• Will bind with other proteins in circulation but
  predominantly fibrinogen because of its high
  concentration.
• Is specific to platelets
• Main function is platelet recruitment
• Aspirin blocks the action of glycoprotein IIb/IIIa

22
Platelet aggregation

• Induced by
• Collagen (skin)
• Proteolytic enzyme (thrombin)
• Biological amines (epinephrine and serotonin)
• Results of the activation is the formation of
  fibrinogen bridge in the presence of calcium-
  makes platelets sticky

23
Block the pathway of platelet by

• Adding substances such as prostaglandin,
  adenosine and nonsteroidal-anti-inflammatory
  agents. Platelets lack biosynthesis ability and
  are enable to synthesize new proteins so cant
  repair itself- have to wait for new platelets to
  form 8-10 day turnover.

24
Platelet Plug

• Needs stabilization through
• Fibrinogen bridge with thrombin- basis for
  stabilization
• Process involves precipitation of polymerized
  fibrin around each platelet- leading to the
  permanent platelet plug.
• Platelet number (N-150-400) and morphology is
  critical in normal function.

25
Quantitative assessment

• Platelet estimation
• Count platelets in 10 oil fields- numerate the
  of platelets/ field
• EX 8, 13, 14, 15, 11, 14, 13, 14, 14, 14
• Average14
• 14 X 20,000 280,000 Approximate estimation of
  normal number of platelets in circulation.

26
Qualitative Assessment

• Patient history of bleeding along with
  performing
• Bleeding Time
• Aggregation agent
• Lumiaggregation

27
Bleeding Time

• In Vivo measurement
• Estimates the ability of platelet plug formation
  and interaction of capillaries and platelets.
• Platelet ability of adhesion to vessel walls
• BT will increase as plt decrease below 100,000
  (Normal BT 3-8 minutes)
• If BT is increased and Plt are within normal
  range or elevated, this is an indication of
  impaired plt function or the presence of
  subendothelial factor.

28
Clot Retraction

• Assess the ability of plts. To contract and form
  a clot.
• Reflects
• and quality of platelets
• Fibrin concentration
• Fibrinolytic activity
• Packed cell volume
• The degree of clot formed reflects the extent
  that fibrin contracts by the volume of RBC.
• Small the HCT Greater the degree of clot
  retraction. The degree of clot retraction is
  proportional to the HCT and the level of the
  blood coagulation factor fibrinogen.

29
Platelet Aggregation

• Based of Borns Method
• Uses agents such as ADP, collagen, epinephrine,
  snake venom, thrombin, ristocetin to promote the
  aggregation of platelets.
• Principle
• Platelets-rich plasma is treated with a known
  substances (snake venom).
• Aggregation is measured with spectrophotometer to
  measure the degree of cloudiness or turbidity
  which is correlated with the known agents
  expected aggregation ability.

30
Platelet adhesion

• In VIVO platelet adhesion occurs as platelets
  attach either to a damaged vessel wall or to each
  other.
• In Vitro have to use a platelet activator
  (epinephrine) to identify the normal or abnormal
  function of platelets and monitor anti-platelet
  therapy.
• Perform turbidmetric aggregometer to determine
  platelet function.

31
Antiplatelet Antibody Assay

• Identifying antibodies against the platelets in
  the plasma
• Complement fixation
• Lysis of Chromium 51 labeled platelet
• Assay platelets bound immunoglobulins
• Competitive inhibition assay

32
Blood Coagulation Factors

• Consist of 12 factors (Numerated by Roman
  numerals- inactive forms)
• Activated forms are represented by the roman
  numeral followed by a suffix (a).
• Common characteristics
• Divided into systems (Intrinsic and Extrinsic,
  exception Calcium and plt. Phospholipids which
  are proteins)

33
Coagulation systems

• Intrinsic contained within the blood
• Extrinsic uses thromboplastin from damaged
  vessels and tissue (outside the blood)
• Factors (synthesized in the liver)
• Fibrinogen (I)
• Prothrombin (II)
• Proaccelerin (V)
• Proconvertin (VII)
• Plasma thromboplastin component (IX)
• Prekallikrein
• High Molecular weight kininogen (HMWK)

34

• Factors Vitamin K dependent
• Prothrombin (II)
• Proconvertin (VII)
• Plasma Thromboplastin Component (IX)
• Stuart factor (X)
• Factors Not Vitamin K dependent
• Fibrinogen (I)
• Proaccelerin (V)
• HMWK
• Prekallikrein

35

• Intrinsic system activates the coagulation
  mechanism, thought to be associated with the
  endothelial injury an stimulant.
• Intrinsic and Extrinsic are described separately
  only for the purpose of evaluation. Both are
  activated simultaneously.
• Factors are synthesized in the Hepatic (liver)
  cells
• Factors react in a cascade or coagulation pathway.

36
Characteristics

• 4 main characteristics of protein clotting
  factors
• A deficiency of a factor results in bleeding
  (exception XII, Prekallikrein and HMWK)
• We know physical and chemical characteristics.
• Synthesis of the factors is independent of other
  proteins
• We can test for the factors

37
Three groups of factors

• Fibrinogen (I, V, VIII, XIII)
• consumed during coagulation, V and VIII decrease
  during blood storage, V and VIII increase during
  pregnancy, presence with inflammation.
• Prothrombin (II, VII, IX, X)
• Vitamin K dependent through dietary and
  intestinal bacteria, inhibited by Warfarin, and
  is stable during storage.
• Contact (XI, XII, Prekallikrein-Fletchers,
  HMWK-Fitzgerald)
• Intrinsic pathway, not consumed during
  coagulation, and is moderately stable upon
  storage.

38
Factor I (Fibrinogen)

• Large stable protein
• Precursor of Fibrin (CLOT)
• Fibrinogen is exposed to thrombin-splits to form
  a fibrin monomer-forms the fibrin clot.
• Fibrinogen gt thrombingt fibrin monomergt fibrin
  clot.

39
Factor II (prothrombin)

• Stable protein
• Needs ionized calcium to convert the thrombin to
  thromboplastin from the intrinsic and extrinsic
  sources
• Half life of 3 days- 70 is consumed during the
  clotting process.
• ProthrombingtCagtextrinsic or intrinsic
  thromboplastingt thrombin.

40
Factor IIa (Thrombin)

• Activated form of prothrombin
• Proteolytic enzyme that interacts with fibrinogen
• Potent platelet aggregate
• Is consumed in the conversion of fibrinogen to
  fibrin
• A unit of thrombin will coagulate 1ml if standard
  fibrinogen in 15 secs _at_ 28C.
• FibrinogengtThrombingtFibrin monomergtpeptides

41
Tissue Thromboplastin (FACTOR III)

• Nonplasma substance that contains lipoprotein
  complex from tissue.
• Tissues Capable of converting prothrombin to
  thrombin.
• Brain
• Lung
• Vascular Endothelium
• Liver
• Placenta
• Kidneys

42
Ionized Calcium (Factor IV)

• Necessary for the activation of thromboplastin
  and the conversion of prothrombin to thrombin.
• Physiologically active form calcium in the body
• Only small amounts are needed for coagulation.

43
Factor V (Proaccelerin)

• Labile globulin protein
• Deteriorates rapidly half-life of 16 hours
• Consumed
• Needed in clotting process and later stages of
  thromboplastin formation.

44
Factor VII (Proconvertin)

• Beta Globulin
• Not essential in the thromplastin generating
  mechanism
• Is not used or consumed during process
• Stable in serum for up to 3 days
• Activates tissue thromboplastin and accelerates
  the production of thrombin from prothrombin.
• Reduced by Vit. K antagonist

45
Factor VIII (Hemophiliac Factor)

• Consumed during the clotting process
• Not present in serum
• Extremely Labile (50 loss within 12 hrs _at_ 4C
  in vitro and 50 loss within 8-12 hrs in vitro.
• Subdivided into
• HMW fraction vWF, VIIIRRCo, VIIIRAg
• LMW fraction VIIIC and VIIIAg

46
Factor IX (Plasma Thromboplastin Component)

• Very stable protein factor, not consumed and is
  stable upon 4C for up to 2 weeks.
• Essential to the intrinsic thromboplastin
  generating system
• Influence the amount of thromboplastin formed.

47
Factor X (Stuart Factor)

• It is an Alpha Globulin- Stable Factor
• Not consumed during clotting-found serum
• With factor V, in the presence of calcium ions
  Factor X forms the final common pathway , which
  the products of extrinsic and intrinsic
  thromboplastin-generating system merge to form
  the thromboplastin that converts prothrombin to
  thrombin.

48
Factor XI (Plasma Thromboplastin Antecedent)

• A beta globulin
• Found in serum partially used up in clotting
  process
• Essential to the intrinsic thromboplastin
  generating mechanism

49
Factor XII (Hageman Factor)

• A Stable factor
• Not consumed during clotting-found serum.
• Adsorption of Factor XII and kininogen (with
  bound prekallikrein and XI) to a surface (glass
  or subendothelium vessels) initiates the
  intrinsic factor
• Surface absorption alters and partially activates
  XII to XIIa by exposing active enzyme protease
  site.
• Feedback mechnism-kallikrein (activated Fletcher)
  cleaves partially activated XIIa to form more
  kinetically effective XIIa

50
Factor XIII (Fibrin Stabilizing Factor)

• In the presence of ionized calcium produces a
  stable fibrin clot.
• Mechanism of coagulation
• The initial stimulus to the final clot formation
• 2 pathways
• Intrinsic
• Extrinsic
• Both converge into a common pathway which leads
  to production of circulating insoluble
  coagulation factors then into fibrin clot.

51
Coagulation Pathway

• Begins with intrinsic or extrinsic pathway
• Factor X activation is the point of convergence
• Factor X is activated by either pathway to
  convert prothrombin to thrombin.

52
Extrinsic Coagulation Pathway

• Started by the entry of tissue thromboplastin
  into circulating blood
• Tissue factors-membrane lipoprotein-extrinsic
  factor
• Platelet phospholipids are not necessary
• Factor VII binds to tissue phospholipids and
  activates VIIagt capable of activating X to Xa in
  the presence of calcium ions
• Tissue factor-factor VII complex dependent on
  concentration of tissue thromboplastin.
• VIIa inactivated by proteolytic cleavage of
  Factor VIIa by Xa
• Factor VII is involved in only the extrinsic
  pathway
• Membranes entering circulation provide a surface
  for the attachment and activation of II and V.
• Final step is fibrinogen to fibrin by thrombin.

53
Intrinsic Coagulation Pathway

• Involved the contact activation factors
• Prekallikrein
• HMW Kininogen
• XII
• XI
• All interact with or on a surface to activate IX
  to IXa
• Factor IXa reacts with Factor VIII, PF 3, and
  calcium to activate X to Xa. In the presence of
  Factor V, Factor Xa activates prothrombin to
  thrombin, converts fibrinogen to fibrin.

54
Surface activators

• Negatively charged solids that participate in
  activating Factor XII.
• Glass and kaolin in vitro
• Elastin
• Collagen
• Platelet surface
• Kallikrein
• Plasmin
• HMW kininogen

55

• Factor XIIa involved in the feedback loop
• Ionized calcium role in the activation of the
  coag factors in the intrinsic pathway.
• Necessary for Factor IX by XIa, not necessary for
  XII, Prekallikrein, Factor XI.
• Final Common Pathway (intrinsic and extrinsic )
• Involves the activation of Factor X to Xa then
  Factor II, prothrombin activated to
  thrombin-which usually circulate as inactive
  factors.

56
Fibrin formation

• Clot formation-conversion of plasma fibrinogen
  into stable fibrin clot
• 3 Phases
• Proteolysis
• Polymerization
• Stabilization

57
Initial phase

• Thrombin (protease enzyme) cleaves to fibrinogen
  which results in a fibrin monomer.
• The fibrin monomer polymerize end to end
• Fibrin monomer covalently linked by Factor XIIIa
  to polymers to form meshwork and fibrin
  solution-converts to a gel.

58
Factor XIII to XIIIa

• 2 Steps
• Thrombin cleaves to alpha chains of factor
  XIII-intermediate inactive form
• Calcium ion causes Factor XIII to disassociates
  forming XIIIa.
• Fibrin forms a loose covering over the injury
  site-closes off the wound. The clot retracts due
  to cells trapped in the clot.
• Can be seen in serum tubes, as clot forms the
  fluid that is being squeezed out of the
  cells-SERUM

59
Fibrinolysis

• Fibrin clot-temporary due to fibrinolysis-break
  down of fibrin clot by enzymatic digestion.
• Clot dissolved by plasmin-by digest of fibrin and
  fibrinogen by hydrolysis to smaller fragments
  which are phagocytized.
• Plasminogen-circulates freely until injury occurs
  as injury occurs plasminogen is activated.
• Activators Enzymes (kinase) found in various
  sites and are endogenous and exogenous form.

60
Tissue activators

• 2 forms
• Enzymes related to Urokinase
• Those not related to Urokinase
• Plasma activators
• Plasma kallikrein
• Factor XI
• XIIa

61
tPA-tissue type plasminogen activators

• Present in minute amounts in vascular
  endothelium.
• Encounters a blood clot-tPA transforms
  plasminogen to plasmin, plasmin degrades the
  clot.
• Natural and synthetic forms of tPA-used to
  dissolve clots

62
Plasmin

• Ensures clot dissolved without proteolysis of
  other proteins
• Activates complement sys.
• Liberates Kinins to kininogens
• Hydrolyzes Factor V, VIII, and XII
• Clot formation can be inhibited by antiplasmins
  and natural occurring inhibitors.
• Natural occurring inhibitors Antithrombin III,
  Alpha 2 macroglobulin inhibitor, alpha 1
  antitrypsin.

63
Laboratory Assessment

• Activated Partial thromboplastin Time (APTT)-
  measures the tine required to generate thrombin
  and fibrin polymers by intrinsic and common
  pathway.
• Looks for the activation of Factor XII to XIIa,
  prekallikrein to kallikrein, XI to XIa to produce
  fibrin.
• Assay Prekallikrein, HMW kininogen, XII, XI,
  VIII, X, V, II, I
• Decreased due to Factor decrease or presence of
  circulating anticoagulant
• Normal 35 seconds

64
Prothrombin Time- PT

• Evaluates the production of thrombin and fibrin
  by the extrinsic and common pathway
• In the presence of Calcium iongt tissue
  thromboplastin forms complex with and activates
  Factor VII
• Provides surface for attachment and activates
  X,V, and II
• Thromboplastin and calcium are added to plasma to
  measure the time required for fibrin clot to
  form.
• Prolonged-indicates deficiency of factor or oral
  anticoagulant
• Normal 10-13 sec
• Measures Extrinsic factors

65
International Normalized Ratio INR

• Use un conjunction with PT
• Value used to correct for the use of different
  reagents of thromboplastin
• Expressed as the ISI-international sensitivity
  index
• Value is missed used and not understood by most.

66
Oral anticoagulants

• 2 types
• Warfarins
• Indanedione derivatives (not used)
• Warfarins
• Drugs that are Vit. K antagonist
• Causes incomplete coagulation-lack calcium
  binding site.
• Activity decreased and assayed by PT
• Usually utilize INR report method to adjust
  dosing of anticoagulant

67
Heparin

• Used in acute therapy
• Prevent new clots from forming
• Causes bleeding, thrombocytopenia and osteopenia
• Need to evaluate CBC, Plts, stool and urine for
  evidence of bleeding.
• Reacts with regulatory protein Antithrombin III
  to inhibit the activation of X to Xa

68
New thromboplastin

• Reagents thromboplastin used to measure PT
• PT for patients with inherited or acquired coag
  factors- PT increased with new reagent.
• Advantages
• Human protein
• Pure
• Free of contaminates
• PT ratio more accurate
• More sensitive

69
Thrombin Time

• Determines the rate of thrombin-induced cleavage
  of fibrinogen to fibrin monomer to fibrin clot.
• Normal lt 20 secs
• Prolongedfibrinogen concentration is lt100mg/dL
• Abnormal results related to the presence of
  thrombin inhibitor or substance in circulation.

70
Fibrinogen levels

• Detects deficiencies of fibrinogen or the
  ability to convert to fibrin.
• Normal 200-400 mg/dL
• Decreased values seen in Liver dis., consumption
  of fibrinogen
• May do titers to assist in evaluation

71
Normal Protective Mechnism Against Thrombosis

• Depends on the balance between
• Procoagulants
• Anticoagulants
• In circulation of the blood
• Body functions that control thormbosis
• Normal blood flow
• Removal of activated clotting factors and
  material
• Natural anticoagulants
• Cellular regulators

72
Natural Anticoagulant System

• Antithrombin III- serine-protease inhibitor
• Heparin Cofactor II-serine-protease inhibitor
• Protein C- major natural anticoagulant
• Vit. K dependent, formed in response to thrombin
• Protein S- Major natural anticoagulant

73
Antithrombin III

• Major inhibitor
• Serpin
• Synthesized by the liver, plts and vascular
  endothelium
• Principle physiological inhibitor of thrombin,
  Xa, IXa, XIa and XIIa
• Normally a slow inhibitor except in the presence
  of heparin (increase 1000 fold)

74
Heparin Cofactor

• Produced by mast cells and endothelium
• Thrombin inhibitors AT III- heparin cofactor and
  Heparin cofactor II
• Inhibits chymotrypsin
• Accelerated by heparin

75
Protein C

• Major natural anticoagulant
• Deficiency or alteration of Prot. C leads to the
  formation of thrombosis
• Vit. K dep.
• Synthesized in liver
• Formed in response to thrombin
• Requires proteolytic cleavage to activate
• Major regulator for coagulation

76

• Activated Protein C is a potent plasma
  anticoagulant
• In the presence of cofactor Protein S -cleaves to
  Va and VIIIa- this decreases the conversion of
  prothrombin to thrombin
• Requires Protein S
• Promotes fibrinolysis
• Production is impaired by Vit.k, liver disease
  and warfarin therapy.
• Decreased in DIC

77
Laboratory Assay

• Antigentic, Chromogenic, Clotting
• Clot base-best assay
• Involves introduction of activator-snake venom
  most often used-activates Protein C-inhibits Va
  and VIIIa-results in prolong aPTT.

78
Protein S

• Vit. Dependent plasma protein
• Cofactor to Protein C
• Regulated by proteolysis
• In circulation-free form 40-functional, 60
  bound
• Accelerates Va and VIIIa inactivation
• Found in platelets
• Increases affinity of activated Protein C 10 fold

79
Assay

• Based on the cofactor activity of Protein S
• Detected by prolong bleeding time
• ELISA
• Antigen/Antibody
• Measure free protein S to estimate bound

80
Cellular Regulators

• Cellular protease
• Blood and Tissue cells
• Platelets and endothelium major regulators

81
Chapter 27 Disorders and Thrombosis

• Disorders that cause abnormal bleeding-involve
  disorders of microcirculation
• Purpura (skin, mucous membrane, internal organs)
• Types of purpura
• Direct endothelial cell damage
• Inherited disease
• Disruption of small venules
• Clots or thrombi
• Malignancy

82
Abnormal Platelet Morphology

• Wiscott-Aldrich-small plts
• May-Hegglin-enlarged plts
• Alports syndrome-giant plts and thrombocytopenia
• Bernard-Soulier Syndrome-very large plts.
• All of the above involve abnormal morphology or
  number of plts in circulation.

83
Thrombocytopenia

• Decreased plts lt 100,000 may see bleeding,
  petechia or purpura
• Result of surgery, organ damage or therapy
• Diseases related to thrombocytopenia
• Deep venous thrombosis, Dissemenated
  intravascular coagulation, pulmonary embolism,
  cerebral thrombosis, myocardial infarction.

84
3 major thrombocytopenic conditions

• Disorder of production
• Disorder of destruction
• Disorder of distribution

85
Disorder of Production

• Decreased production in the megakaryocytic cell
  line-Bone marrow
• Acquired damage of BM, infections or nutritional
  def.
• Hereditary disorders Fanconis, aplastic
  anemia, X-linked amegakaroycytic thrombocytopenia

86
Disorders of destruction or utilization

• Due to immune mechanism
• Antigen, antibody or complement
• Drugs
• Quinidine, morphine, snake venom, heroin
• Bacterial exposure-plasmodium falciparium
• Induces antibody immune complex.

87
Increased utilization of Platelets

• Idiopathic Thrombocytopenic purpura (ITP)-no
  known origin
• 2 type adult and childhood
• Adult-most common (10-40yrs old), autoantibody,
  treat with cortisteroid or spleenectomy.
• Childhood more common than adult form, abrupt
  onset of disease and spontaneous remission

88
Clinical signs and symptoms

• Purpura
• Epitaxis
• Gingival bleeding
• Hematuria
• GI bleeds
• Intracerebral Bleed

89
Laboratory Data

• Decreased Platelets
• Assay antibody to glycoprotein
• Antibody-antiplatelet
• Treatment restore (transfusion) if no antibody
  present, immunoglobulin, spleenectomy.

90
Disorders of platelets Distribution

• Result of pooling of platelets in spleen
• Disease
• Liver-cirrhosis
• Lymphomas and leukemia's
• Lipid disorders
• Gauchers

91
Thrombcytosis

• Normal to increased Plt.
• Grouped by
• Reactive or benign Blood loss, inflammation,
  drugs, spleenectomy, malignancy, anemia
• Hematologicalmyeloproliferative disease and
  autoimmune hemolytic anemia

92
Qualitative characteristics

• Normal , but no functional
• Examine medical history
• Bleeding time
• Platelet aggregation
• adhesion
• antibody

93
Types of Platelet Dysfunction

• Acquired-due to blood plasma inhibitory
  substance, myeloproliferative dis., malignancy,
  autoimmune disorders.
• Drug induced Aspirin
• Hereditary inheritance of structural or
  biochemical defect (Bernard-Soulier, Glazmans,
  Hereditary storage Pool.

94
Disorders related to Blood Clotting Factors

• Abnormal clot or fibrin formation due to disorder
  of coagulation factor
• Defect in production Vit. K Def. (factor II,
  VII, IX, X), liver dis. Hemophilia, vWD
• excessive destruction
• pathological inhibition

95
Hereditary Clotting Defect

• 2 Type Hemophilia A and von Willdebrand- both
  inactive VIII
• Hemophilia
• Related to the cloning of VIII and identification
  of mutation in VIII-lack VIII
• Corrected by giving the patient factor VIII
  product-cryopreciptant

96
Von Willebrand Disease

• Decrease in HMW and LMW portion
• Increase bleeding time
• Def. in Factor VIIIc, VIIIcAg, VEFAg ristocetin
  cofactor, VIII-vWF complex
• Most common hereditary bleeding disorder.
• Abnormal plt function

97
Von Willebrand Factor

• Bases for forming normal plt. Thrombus
• Binds to specific sites on plts and
  subendoithelium to form bridge-to form normal
  plt. Thrombus.
• Decreased levels leads to inability to form
  bridging action- increase bleeding time or rate
• Various Types depending on amount of circulating
  protein.

98
Acquired von Willebrand

• Associated with autoimmune and myeloproliferative
  disorders
• Circulating antibody to vWF or absorption of
  coagulation component
• Bleeding more severe in acquired state
• Decreased vWF activity

99
Pseudo-von Willebrand

• Rare disorder-looks like VWD
• Decreased levels of vWF in plasma
• Platelet abnormality
• Increased levels of vWF associated with stress,
  inflammation, postsurgical, pregnancy, renal
  dis., Diabetes, etc.

100
Lab Findings

• Bleeding Time Mild to moderate increase
• Platelet decreased
• Platelet aggregation ristocetin-abnormal, with
  other activators normal aggregation

101
Other Hereditary Diseases

• Hemophilia B or Christmas Disease
• Non-sex-linked , occurs in 1/50,000 of the
  general population
• Clinically indistinguishable for Hemophilia A

102

• Hemophilia C deficiency in Factor XI
• Genetic defect-autosomal recessive trait
• Seen in population of Jewish decent
• Mild disorder
• Fibrinogen Deficiency
• Genetic disorder
• Involves a defect or dysfunctional molecule in
  circulation
• Misc. Diseases
• Factor XII Def. rare, no clinical signs of
  disease (bleeding)
• Factor XIII Def. rare, associated with
  spontaneous abortion or poor wound healing.
• Table 27.12, 27.13

103
Disorders of Destruction and consumption

• Results in thrombosis and damage to organs ,
  impedes blood flow and causes ischemia
• Induced in vivo by enzymatic degradation or
  pathological activation- result of a bites from
  snake or spider that contain enzyme that degrades
  the fibrinogen
• Disease that can cause excess utilization or
  consumption of caog. Factors trauma, burns,
  obstetrical complications, shock, malignancy,
  intravascular hemolysis, septicemia.

104
General Features of Fibrinolysis

• Primary associated with conditions of gross
  activation of fibrinolytic mechanism-leading to
  the consumption of coag. Factors. No evidence of
  fibrin deposit. Large amount of plasminogen
  activator enters into circulation

105

• Secondary Fibrinolysis or DIC
• Different from primary in the fibrin formation.
  In DIC there is excessive clotting and
  fibrinolytic activity occurring.
• Excess or increased amount of Fibrin Split
  Product (FSP) in DIC, due to the excessive
  clotting that is occurring in the body.
• Table 27.14

106
DIC

• A.K.A Consumptive Coagulopathy or Defibrination
  Syndrome
• Result of another complication or disease
  process, doesnt usually occur alone.
• Due to various traumas or diseases-that lead to
  tissue thromboplastin activation of coagulation.
  Have Excess thrombin formation.
• Thrombin is the central mechanism of consumptive
  coagulopathy leading to clot formation-that leads
  to fibrinolysis.

107
Fibrinolytic System

• Plasminogen converted to plasmin, alpha-2
  antiplasmin is a fibrinloytic inhibitor that
  copes with plasmin. The more plasmin produces
  in fibrinolytic process, the more alpha-2
  antiplasmin in consumed, leads to increased
  activation mechanism and less inhibitors to stop
  the process. This is not compatible with life.

108
Inhibitor systems

• The bodys way of stopping the process
• 2 major inhibitor systems
• Antithrombin system
• Protein C and S system
• Both inhibitor systems are consumed in the DIC
  process, therefore the body has no way of
  stopping the process.

109
Alternate forms of DIC

• DIC Clotting and Lysis strongly activated
• DIC Clotting predominates with little or no
  lysis
• Primary Fibrinogenolysis Lysis activated
• The patient is forming clots and lysis the clots
  at abnormally high rates. Based on the
  predominate occurrence (clot or lysis) determines
  the form.

110
Role of Factor VIII in DIC

• Close relationship between VIIIC (procoagulant)
  and VIIICAg (antigen), VIIICAg is activated to
  lesser extent than VIIIC-which is destroyed by
  minute amounts of thrombin, plasmin and activated
  Protein C. The degree of DIC is related to the
  inactivation Factor VIIIC
• Measure the amount of Factor VIIIC and VIIICAg
  to determine the degree severity of DIC

111
Role of Protein C in DIC

• It is a major regulatory mechanism of hemostasis.
• Decreases the rate of thrombin formation by
  controlling Factor Va and VIIIC-rate limiting
  steps of coagulation
• If Protein C is being consumed too rapidly its
  regulatory ability is decreased-leading to
  uncontrollable thrombi.
• Assay for Protein C used to monitor the course of
  DIC, during initial stage Protein C antigen and
  activity decreased (24-48 hrs) before returning
  to normal in the recovery stage.

112
Role of Thrombin

• Over production of thrombin, which activates
  fibrinolysis- activates protein C.
• Excess thrombin binds Protein S (which is needed
  for protein C to be activated, therefore there is
  a increase in activation of Protein C in plasma.
• Negative feedback loop-used to slowdown the
  process or stop DIC.
• Excess thrombin can be decreased by activated
  protein C

113
Clinical Signs and Symptoms

• Acute (rapid onset, life threatening), see
  decrease in fibrinogen and platelets, hemorrhagic
  complications
• Chronic more common, but difficult to diagnose,
  easily converts to acute phase
• Clinical signs petechia, purpura, hemorrhagic,
  bruising, bleeding, etc.
• Table 27.15 (pg.437)

114
Conditions similar to DIC

• TTP Thrombotic thrombocytopenia Purpura
• PRDS pediatric Resp. Distress Syndrome
• ARDS Adult Resp. Distress Syndrome
• HUR Hemolytic Uremic Syndrome
• Eclampsia
• Rocky Mountain Spotted Fever

115
Laboratory Test

• Coagulation assay must be compared and vary
  greatly.
• Platelet count- vary, if decreased then
  fibrinogen decreased
• Fibrinogen level- decreased (correlates with
  plts.)
• Fibrin Degradation Product-positive
• Factor V-vary
• Ethanol gelatin test
• Thrombin time
• Reptilase test
• Fibrinogen Split Product key feature
• Prolonged APTT and PT

116
Disorders Related to Elevated FSP

• Normal FSP 10µg/ml
• Increased levels indicate renal dysfunction
  (normal urinary values 0.25 µg/ml)
• See increased levels in neonatal sepsis or DIC
• Pulmonary Embolism FSP100µg/ml
• Obstetric problems see FSP as high as
• 80 µg/ml

117
Hypercoagulable State

• Clot formation due to hypercoagulation and
  fibrinolysis in impaired.
• See vascular damage
• Inherited or disorder related
• Table 27.18

118
General features

• Vascular damage occurs and blood flow slows
  because of the clot formation
• Due to the formation of clot, blood flow slows
  increasing the risk of clot formation-increasing
  the viscosity and accumulation of cells- end
  result clot.
• Platelets start detaching easier due to the slow
  blood flow, increase of plts in circulation
  increases the chance of clot formation

119

• Blood clotting factors-based on increase or
  decrease of the different levels in influence the
  blood clotting ability of the circulating blood.
  Increased in coagulation factors have a tendency
  to form thrombi.
• Certain disease process have a tendency to form
  clots.
• Certain medications tend to effect certain
  coagulation factors that can lead to
  hypercoagulation.

120

• Circulating Anticoagulants
• Acquired inhibitors of clotting proteins
• (Specific and nonspecific)
• Introduced by exposure to activators or
  transfusion of blood product, disease process,
  etc. which leads to factor def.
• May be in circulation for months to years.

121
Specific inhibitors

• Lupus anticoagulant
• Found in 10 of SLE patients
• Most common
• A.K.A. antiphospholipid antibody
• Inhibitor directed against the in vitro
  phospholipid component.

122

• Factor VIII inhibitor
• Most common specific inhibitor
• Found in Factor VIII Def.
• Develop easily when exposed
• Seen in immunological disorders

123

• Factor IX inhibitor
• Found in 2-3 of Factor IX def.
• Associated with transfusion of blood products.
• Factor V inhibitor
• Rare
• Associated with exposure to streptomycin
• Fibrinogen, Fibrin and Factor XIII inhibitor
• Associated with transfusion of plasma products
  and antiturberculosis drugs.

124

• Factor II, VII, IX and X inhibitors
• Rare
• Various reasons for development-congenital,
  immune, amyloidosis
• Factor XI and XII inhibitor
• See in SLE patients, Waldenstroms, and drug
  induced

125
Clinical presentation

• Lupus Anticoagulant not associated with bleeding
  due to factor def, but thrombocytopenia. Do have
  problems with thromboembolism.
• Specific factors usually no history of
  bleeding, but may have hemorrhage episode or
  hemophilia patients not responding to blood
  product.

126

• Non-hemophilia pts. With acquired inhibitor
  VIII-see major bleeds
• Factor V inhibitor-clinical bleeding
• Factor XIII, II, VII, IX and X fibrin or
  fibrinogen result in severe hemorrhagic events.
• Lab Data
• Increased PT, APTT
• Mixing study used to detect inhibitors-prolonged
  in the presence of inhibitors
• Bethesda assay
• Antiphospholipid antibody

127
Impaired Fibrinolysis

• Genetic or acquired
• Patient is predisposed to thrombosis
• Associated with hypercholesterolemia
• Def. in actor VIII and V

128
Protein C Deficiency

• Thrombotic episodes
• Acquired or congenital
• See in DIC, Liver dis., Vit K Def., and oral
  anticoagulants
• Thrombotic complication
• Table 27.20, pg 441

129
Types of Protein C def.

• Type I
• Type II
• Type IIa
• Type IIb
• All are related the amount of antigenic levels of
  protein C and the degree of impairment.

130
Activated Protein C Resistance

• New test and disease that causes thrombotic
  problems
• Inherited def. of anticoagulant cofactor
• Identical to inactivated Factor V

131
Protein S Deficiency

• More common than def. Protein C
• Congenital def. associated with increase
  recurrent juvenile venous and arterial
  thromboembolism.
• Congenital Protein S Def
• 3 types I-III

132
Antithrombin III Def.

• Hereditary defect due to
• Quantitative def. of AT-III
• Type I-represents majority of cases
• Type II- characterized by decrease heparin
  cofactor activity, see reoccurring DVT
• Congenital-symptoms develop 10-30 yrs old.
• Acquired due to decreased synthesis, increased
  consumption or drug induced.

133
Heparin Cofactor Def.

• Recurrent thrombotic complication
• Inherited disease
• Associated with DIC development
• Signs and symptoms thrombophlebitis, DVT, PE
• Associated with 5-10 Protein S, 7 Protein C,
  2-4 AT-III

134
Venous Thromboembolism

• Hereditary or acquired
• 2 Groups
• 1. Patients with diseases or predisposed illness
  or factor.
• 2. Patient with factor Def. or other factor
  (pregnancy or oral contraceptive).
• Lab assessment TEG, check fibrinogen formation,
  presence of activated coagulation factors, PT,
  APTT, Prot. C, AT-III.