By Dr Vishal Hudgi

1. NORMAL COAGULATION,
COAGULOPATHY AND
HEMORRHAGE
DR VISHAL V H,
JIVAS, BANGALORE

2. INTRODUCTION
• Coagulation is a physiologic defense mechanism aimed at maintaining the integrity of the
circulatory system in the setting of vascular injury.
• Vascular endothelial cells, blood and extravascular tissue maintain blood flow fluidity or
produce an integrated response to prevent blood leakage by localized clotting at the site of
vascular injury.
• The processes of blood coagulation and fibrinolysis are the primary defense systems of
the vasculature.
• Hemostasis refers to multiple discrete processes that center on thrombin generation, fibrin
clot formation, and fibrin clot dissolution.
• A balance among procoagulant, anticoagulant, and fibrinolytic factors is required to prevent
uncontrolled bleeding or, conversely, excessive clot formation.

3. Normal hemostasis comprises a series of regulated processes that maintain blood in a fluid,
clot free state in normal vessels while rapidly forming a localized hemostatic plug at the site
of vascular injury.
Achieved through the following mechanisms:
1. Transient arteriolar vasoconstriction
2. Platelet adherence, activation and aggregation
3. Coagulation
4. Fibrinolysis

4.  PRIMARY HEMOSTASIS - It takes place when there are injuries to small vessels during which
the affected vessels contract to seal off the wound and platelets are mobilized, aggregate, and
adhere to components of the subendothelium of the vasculature. Platelet adhesion requires the
presence of various factors such as von Willebrand factor (vWF) and platelet receptors (IIb/IIIa
and Ib/IX).
Secondary hemostasis - involves the response of the coagulation system to vessel injury. It is
required to control bleeding from large wounds and is a continuation of the primary hemostatic
mechanisms.
• Whereas the outcome of primary hemostasis is the formation of the platelet plug, the outcome of
secondary hemostasis is the formation of a thrombus.

6. MAJOR COMPONENTS OF NORMAL
COAGULATION
• PROCOAGULANT
• ANTICOAGULANT
• FIBRINOLYTIC PROTEINS
• ENDOTHELIUM AND PLATELETS

9. VITAMIN-K–DEPENDENT PROTEINS
• These are synthesized in the liver and play central roles in both the procoagulant or
anticoagulant pathways.
• The family includes the procoagulant factors VII, IX, X, and prothrombin and the
anticoagulants protein C, protein S, and protein Z.
• Vitamin K is essential for the biosynthesis of these clotting factors by participating in a
cyclic oxidation and reduction process that converts 9 to 13 amino-terminal glutamate
residues into γ-carboxyglutamate (Gla) residues. This posttranslational modification
enables the vitamin-K-dependent proteins to interact with Ca2+ (or calcium ions) and
appropriate membranes.
• Inhibition of the Gla residue modification is the basis for “blood thinning” anticoagulant
therapy with coumarin derivatives.

10. FIBRINOLYSIS PROTEINS
• Clot formation is integrated with clot dissolution. The mechanisms of clot dissolution center
on fibrin-specific reactions.
• The key proteins involved are
1. Plasminogen; the plasminogen activators- tissue plasminogen activator (t-PA) and
urokinase plasminogen activator (u-PA)
2. The inhibitors PAI-1, α2-antiplasmin, and TAFIa(thrombin-activatable fibrinolysis inhibitor)

11. ANTITHROMBOTIC PROPERTIES OF NORMAL
ENDOTHELIUM
• Prostacyclins ie PGI2 and nitric oxide produced by endothelium impedes their adhesion, potent
vasodilators, inhibit aggregation
• Endothelial cells also produce Adenosine diphosphatase which degrades ADP further inhibiting platelet
aggregation.
• Coagulation factors – the inhibitory effects are mediated by factors expressed on endothelial surfaces
particularly heparin like molecules, thrombomodulin, and tissue factor pathway inhibitor..
• Heparin like molecules act indirectly by enhancing the inactivation of thrombin by antithrombin III.
• Thrombomodulin binds to thrombin thereby modifying the substrate specificity of thrombin so that it cleaves
and activates protein C instead of fibrinogen.
• Fibrinolysis - endothelial cells synthesize tissue type plasminogen factor that cleaves plasminogen to
plasmin which in turn cleaves fibrin to degrade thrombi.

12. PROTHROMBOTIC PROPERTIES OF INJURED/ACTIVATED
ENDOTHELIUM
• Activation of platelets - endothelial injury brings platelets into contact with Subendothelial
ECM which constituents von Willebrand factor . vWF is held fast to the ECM through
interactions with collagen as well as Gp1b found on the surface of platelets allowing it to as
glue that binds platelets tightly to injured vessel walls.
• Activation of clotting factors – in response to TNF / IL-1 or endotoxin endothelial cells
produce tissue factor the major in vivo activator of coagulation and downregulate
thrombomodulin. Also bind coagulation factors IXa and Xa augmenting the catalytic
activities.
• Antifibrinolytic effects – activated endothelial cells secrete plasminogen activator inhibitors
which limit fibrinolysis.

13. THE ENDOTHELIUM IN HEMOSTASIS

14. PLATELETS
• Platelet function depends on several integrin family glycoprotein receptors, a
contractile cytoskeleton and 2 types of cytoplasmic granules:
- Alpha granules – express the adhesion molecule P-selectin on their membranes and
contain fibrinogen, fibronectin, factors V & VIII , platelet factor 4 , platelet derived
growth factor , transforming growth factor beta.
- Dense bodies (delta granules) - ADP, ATP , ionized calcium , histamine, serotonin ,
epinephrine.
1. PLATELET ADHESION - Depends on vWF and Gp1b. Under stress( i.e in flowing
blood) vWF undergoes a conformational change allowing it to bind to collagen in
the ECM and to platelet Gp1b.

15. 2. PLATELET ACTIVATION –
• Platelet adhesion lead to an irreversible shape change and secretion of both granule
types ( platelet activation)
• Calcium and ADP released are important as Calcium is required by several
coagulation factors and ADP is a potent activator of resting platelets.
• Activated platelets synthesize thromboxane A2 (TxA2) a PG that activates additional
nearby platelets as well play an important role in platelet aggregation.
• Subtle membrane changes include an increase in the surface expression of
negatively charged phospholipds providing binding sites for both calcium and
coagulation factors and a conformation change in platelet GpIIb /IIIa that permits it to
bind to fibrinogen.

16. 3. PLATELET AGGREGATION-
• Prompted by bridging interactions between fibrinogen and GpIIb/IIIa receptors on
adjacent platelets.
• Concurrent activation of the coagulation cascade generates thrombin which stabilizs
the platelet plug through two mechanisms:
1. Thrombin activates a platelet surface receptor (protease activated receptor[PAR])
which in concert with ADP and TxA2 further enhances platelet aggregation. Platelet
contraction follows creating the secondary hemostatic plug.
2. Thrombin activates fibrinogen to fibrin

17. ACTIVATION, SECRETION, AND AGGREGATION OF
PLATELETS.

18. COAGULATION CASCADE

19.  Intrinsic pathway
• The initial reaction is the conversion of
inactive factor XII to active factor XIIa.
• Factor XII is activated in vitro by exposing
blood to foreign surface (glass test tube).
• Activation in vivo occurs when blood is
exposed to collagen fibers underlying the
endothelium in the blood vessels.
 Extrinsic pathway
• Requires contact with tissue factors external
to blood.
• This occurs when there is trauma to the
vascular wall and surrounding tissues.
• The extrinsic system is triggered by the
release of tissue factor (thromboplastin from
damaged tissue), that activates factor VII.
• The tissue thromboplastin and factor VII
activate factor X.

20. FIBRINOLYSIS AND EXTRACELLULAR MATRIX DEGRADATION.
α2-AP, α2-Antitrypsin; ECM, extracellular matrix; t-PA, tissue plasminogen activator; TAFI,
thrombin activatable fibrinolysis inhibitor; u-PAR, u-PA receptor.

21. BLOOD COAGULATION MONITORING
• Plasma Clotting Tests
1. Prothrombin Time-
- This assay depends on the infusion of Ca2+ and exogenous TF-lipid preparation
(thromboplastin, recombinant or prepared from human placenta or rabbit brain) to citrated
plasma.
- PT results are standardized by the international normalized ratio (INR).
- This assay is most sensitive to factor II, factor V, factor VII, factor X, and fibrinogen. The
three main uses of the PT assay are the monitoring of warfarin therapy, the assessment of
liver function in patients with severe liver disease, and the screening for deficiencies in the
extrinsic and common pathways.

22. 2. Activated Partial Thromboplastin Time
• The continuity of the intrinsic pathway of coagulation is assessed by the aPTT, which
involves adding phospholipid, Ca2+, and a foreign “surface” (e.g., kaolin or silica) to
citrated plasma in the absence of TF.
• This test evaluates the ability of the intrinsic pathway catalysts (i.e., factor XII, prekallikrein,
HMWK, factor XI, factor VIII, and factor IX) and components of the common pathway (i.e.,
fibrinogen, prothrombin, factor V, and factor X) to produce a clot.
• The primary utility of the aPTT is that it provides identification of the congenital hemostatic
defects associated with hemophilia A (factor VIII deficiency) and hemophilia B (factor IX
deficiency).
• The aPTT is also used to monitor therapy with unfractionated heparin and to detect the
lupus anticoagulant.

23. 3. Thrombin Time
• The TT test detects direct inhibitors of thrombin or fibrin polymerization. It is particularly
sensitive to heparin, fibrin degradation products, and hypofibrinogenemia or
dysfibrinogenemia.
• This screening test is useful in evaluating a prolonged PT or aPTT by discriminating
between a problem in thrombin generation and the inhibition of thrombin activity.

24. WHOLE-BLOOD ASSAYS
• Activated Clotting Time- Activated clotting time (ACT) is a point-of-care coagulation test
designed to monitor heparin therapy in the clinical situations in which intensive
anticoagulation is required. Similar to partial thromboplastin time (PTT), ACT reflects time
of clot formation via the intrinsic coagulation pathway by the addition of factor XII activators
(eg, diatomaceous earth [Celite], kaolin, glass beads, ellagic acid) and increases linearly to
relation to the heparin concentration
• It is one of the most frequently performed coagulation assays and has shown utility as a
point-of-care evaluation of the hemostatic response in surgical and interventional suites to
control treatment with intravenous unfractionated heparin during vascular procedures.

25. THROMBOELASTOGRAPHY
• The coagulation cascade is a dynamic process dependent on many factors. It involves interaction
between primary hemostasis, platelet clot formation, secondary hemostasis, thrombin generation, and
fibrinolysis
• TEG monitors the thrombodynamic properties of blood as it is induced to clot under a low shear
environment resembling sluggish venous flow.
• The patterns of change in shear- elasticity enable the determination of the kinetics of clot formation,
growth as well as the strength and stability of formed clot.
• These devices are viscometers that measure the increasing viscosity of blood during the coagulation
process, producing a time-based record.
• The viscoelastic measurement of a patient's blood sample is increasingly being used in clinical
settings. These settings include cardiac surgery, liver transplantations, sepsis trauma, obstetrics,
anticoagulant activity and treatment with fibrinolytic agents

27. COAGULOPATHY AND HEMORRHAGE
• “Coagulopathy” is a term employed loosely in the literature and in the clinical setting. It is
applied to patients without identifiable coagulation abnormality but with clinical bleeding or
recurrent thrombosis as often as to patients with disseminated intravascular coagulopathy
and significantly abnormal coagulation parameters.
• Coagulation is a physiologic defense mechanism aimed at maintaining the integrity of the
circulatory system in the setting of vascular injury. There is a critical balance between
coagulation and fibrinolysis aimed at preventing pathologic hemorrhage and thrombosis.
• The vascular surgeon is thus tasked with preventing adverse events by achieving
adequate hemostasis without effecting extensive thrombosis, and an understanding of
normal hemostasis

28. DIAGNOSIS AND PREOPERATIVE SCREENING FOR BLEEDING DISORDERS
• Identifying patients preoperatively who are at risk for bleeding allows the surgeon to initiate
corrective treatment before performing a surgical procedure and to plan for optimal
perioperative management.
1. History and Examination
2. Laboratory Testing
• Risk Stratification- Rapaport devised the following four-level stratification scheme to
determine the need for preoperative laboratory testing according to the patient's clinical
status and bleeding history and the planned operation

29. • Level I- Patients who have no bleeding history and will undergo minor procedures, such as
lipoma excision. No further hematologic evaluation is required
• Level II-Patients who have no previous bleeding history but will undergo a major operation.
Normal activated partial thromboplastin time(aPTT) and platelet count should effectively
eliminate the risk of life-threatening bleeding.
• Level III- Patients with bleeding history and those whose procedure might impair hemostasis
(e.g., cardiac or neurosurgical interventions). preoperative evaluation of the following factors is
appropriate:
1. bleeding time and platelet count
2. prothrombin time (PT) and aPTT
3.factor XIII deficiency and fibrinolysis screening
• Level IV- A history or physical findings highly suggestive of abnormal hemostasis, and the
surgical procedure is not a factor. In addition to performing the tests indicated for level III
patients, the following should be considered (especially if the results of level III testing are
normal):
1. Bleeding time after the administration of 600 mg of aspirin— to uncover von Willebrand
disease (vWD) or a qualitative platelet disorder
2. Factor VIII and factor IX levels
3. Thrombin time (TT)—to detect dysfibrinogenemia

30. COAGULOPATHIES
INHERITED
COAGULOPATHIES
1. Platelet Disorders
• von Willebrand Disease
• Giant Platelet Disorders
• Glanzmann's Thrombasthenia
• Storage Pool Disorders
2. Hemophilia
ACQUIRED
COAGULOPATHIES
1. Platelet Disorders
2. Uremia
3. Vitamin-K-Related Disorders
4. Disseminated Intravascular Coagulation
5. Primary Fibrinolysis

31. OTHER COAGULOPATHIES
1. DRUG-INDUCED COAGULOPATHIES
2. HYPOTHERMIA
3. ACIDOSIS
4. DILUTION

32. PLATELET DISORDERS
• Inherited platelet disorders are rare conditions with varying degrees of phenotypic severity.
These disorders affect multiple aspects of platelet function, namely aggregation, secretion,
adhesion, and procoagulant activity.
• There are a large number of rare conditions, the most common of which are described
below.
1. von Willebrand Disease
2. Giant Platelet Disorders
3. Glanzmann's Thrombasthenia
4. Storage Pool Disorders

34. VON WILLEBRAND DISEASE
• von Willebrand factor (vWF) plays an important role in primary hemostasis by binding to
both platelets and endothelial components, effecting formation of an adhesive bridge
between them.
• vWF also contributes to clot formation by acting as a carrier protein for factor VIII.
• von Willebrand disease (vWD) is the most common inherited bleeding disorder.
• Clinical manifestations range from nil to severe bleeding, depending on the level of
functional, circulating vWF.
• vWD is classified into three major types on the basis of clinical laboratory test results and
genetic mutations

35. • Treatment decisions are based on severity of symptoms and type of vWD.
• Symptomatic patients should avoid NSAIDS.
• Desmopressin (DDAVP) is effective in patients with type I vWD perioperatively and in
those with mild to moderate bleeding episodes.
• Patients with type 3 and severe forms of type 2A, 2B, and 2M disease usually require
replacement therapy with vWF, factor VIII–vWF concentrates, or cryoprecipitate

36. GIANT PLATELET DISORDERS
• Giant platelet disorders are a group of rare disorders characterized by thrombocytopenia,
large platelets, and variable bleeding symptoms.
• They are generally subcategorized into four groups:
1. structural defect (e.g., Bernard-Soulier syndrome with glycoprotein abnormalities),
2. abnormal neutrophil inclusions (e.g., May-Hegglin anomaly),
3. with systemic manifestations (e.g., hereditary macrothrombocytopenia with hearing loss),
4. with no specific abnormalities (e.g.,Mediterranean macrothrombocytopenia).

37. BERNARD-SOULIER SYNDROME
• The most common of these platelet disorders, is characterized by thrombocytopenia, large
platelets, and bleeding.
• It is attributed to dysfunction or absence of the GPIb/ IX/V complex, which is a primary adhesion
receptor of platelets.
• The disorder manifests early in life as bleeding symptoms, epistaxis or gingival or cutaneous
bleeding. Frequently, a severe hemorrhagic episode is noted after surgery (e.g., circumcision).
• Laboratory findings include thrombocytopenia and a prolonged bleeding time with normal clot
retraction.
• Management of patients with this syndrome usually entails education and avoidance of minor
trauma.
• In the event of significant hemorrhage, platelet transfusion is generally indicated.

38. GLANZMANN'S THROMBASTHENIA
• Glanzmann's thrombasthenia is an autosomal recessive disease with a large number
of reported mutations.
• A defect in GP-IIb/IIIa renders platelets unable to aggregate.
• Normal GP-IIb/IIIa allows platelets to bind soluble proteins and vWF.
• In Glanzmann’s thrombasthenia, platelets can attach to exposed endothelium but
cannot form aggregates.
• A wide spectrum of phenotypic severity is reported, but mucocutaneous bleeding and
the absence of platelet aggregation are classic findings.
• Significant bleeding episodes typically require platelet transfusion.

39. HEMOPHILIA
• The hemophilias are inherited bleeding disorders caused by low concentrations of specific
coagulation factors.
• Pathogenesis-The most common hemophilias are X-linked deficiencies of factor VIII
(hemophilia A) and factor IX (hemophilia B). Factor XI deficiency (hemophilia C) is a less
common autosomally transmitted disorder. Bleeding in hemophilia results from a failure of
secondary hemostasis. Although a normal platelet plug forms, stabilization of the plug by fibrin
is defective owing to inadequate amounts of thrombin.
• Diagnosis-Hemophilias A and B are clinically indistinguishable. A diagnosis of hemophilia is
confirmed by an assay for the specific factor. Factor VIII deficiency secondary to hemophilia A
requires distinction from vWD by assays for Vwf.
• Most cases of hemophilia are identified via family history. Whereas severe disease is typically
diagnosed by 2 years of age, mild or moderate disease may not be recognized until adulthood.
The hallmark of severe hemophilia is spontaneous bleeding into joints and muscles

40. MANAGEMENT
• The primary goal of treatment is to sufficiently increase the concentration of the missing
factor to stop or prevent spontaneous, traumatic, or surgical hemorrhage.
• DDAVP can sufficiently raise factor VIII levels in patients with mild hemophilia A, factor
concentrations are typically required for more significant disease. Multiple factor VIII and IX
concentrations are available as either recombinant or plasma derived products.
• In some patients who undergo long-term replacement therapy, antibodies against factors
VIII and IX develop. For these patients, recombinant factor VIIa (rFVIIa) or activated
prothrombin complex concentrates might be necessary to achieve hemostasis.

41. ACQUIRED COAGULOPATHIES
 Platelet Disorders
• Acquired platelet dysfunction are due to uremia, liver dysfunction, cardiopulmonary bypass,
hypersplenism, hematologic malignancy, thrombotic thrombocytopenic purpura, and immune
thrombocytopenic purpura.
• These processes can result in quantitative or qualitative platelet deficiencies and should be
considered in any investigation of abnormal bleeding, especially that accompanied by
thrombocytopenia.
• Liver disease evokes thrombocytopenia via portal hypertension with splenic sequestration as well
as by decreased thrombopoietin production.
• Cardiopulmonary bypass and mechanical assist devices place platelets in contact with non
physiologic machine surfaces, which result in pathologic alterations in surface glycoprotein
expression. Activation of these glycoproteins results in granule release as well as decreased
endothelial adhesion and aggregate formation.

42. VITAMIN-K-RELATED DISORDERS
• Factors II, VII, IX, and X as well as proteins C and S require vitamin K for activation. Functional
impairment of these factors is due to failure of vitamin-K-dependent carboxylation.
• The cause is typically lack of vitamin K (malnutrition or malabsorption due to biliary obstruction
or gut bacterial overgrowth) or pharmacologic blockade of vitamin K (warfarin).
• Treatment entails either functional factor replacement (FFP) or vitamin K (allowing carboxylation
of patient's factors) to address active bleeding or in anticipation of surgical intervention.
• FFP acts quickly as a direct replacement without the need for enzymatic reactions; it has an
immediate effect that lasts about 6 hours. Vitamin K takes at least 6 hours to take effect but
exerts a more durable reversal.

43. DISSEMINATED INTRAVASCULAR COAGULATION
DIC is systemic activation of the coagulation cascade that induces both thrombosis and hemorrhage.
Characteristics
• Widespread activation of coagulation
• intravascular formation of fibrin
• thrombotic occlusion of small vessels
• contributes to multiple organ failure in conjunction with haemodynamic and metabolic consequences
• Depletion of platelets and clotting factors
• severe bleeding

44. MECHANISMS FOR COMMON CAUSES OF DISSEMINATED INTRAVASCULAR
COAGULATION
• Sepsis - Extrinsic pathway
- Thrombin generation
- Suppression of protein C/thrombomodulin system
• Major tissue injury - Direct endothelial injury
-Release of phospholipids and enzymes to circulation
• Malignancy -Expression of tissue factor by circulating tumor cells
-Procoagulant: calcium-dependent cysteine protease
-Directly activates factor X

45. Pathogenesis
• DIC is primarily caused by uncontrolled production of thrombin, which leads to systemic
intravascular deposition of fibrin. The inciting factor is generally vascular injury or
intravascular exposure to a procoagulant.
• In DIC, the inhibitory mechanisms become dysfunctional or leading to the production of
excess thrombin.
• The increased circulating levels of thrombin provoke greater fibrin production with
microvascular deposition. Thrombosis of the microvasculature causes the end-organ
damage seen in severe DIC.
• The systemic thrombosis activates t-PA, which causes thrombolysis, consumptive
coagulopathy, and bleeding diathesis.

46. Treatment
• Correction of the precipitating factor. Supportive therapy generally necessitates replacement of
clotting factors and platelets while the inciting process is addressed.
• Goals of resuscitation include a fibrinogen level over 100 mg/dL.
• Maintaining normothermia and adequate tissue perfusion.
• In septic patients, broad-spectrum antibiotics, abscess drainage, and debridement of infected or
necrotic tissues is critical.
• Platelet infusions (for thrombocytopenia)
• Cryoprecipitate (for hypofibrinogenemia)
• Fresh-frozen plasma (for replacement of other coagulation factors and natural inhibitors).

47. DRUG-INDUCED COAGULOPATHIES
1. Heparins
2. Thrombin Inhibitors
3. Oral Anticoagulant
4. Direct Oral Anticoagulants
5. Antiplatelet Agents
6. Therapeutic Thrombolysis

48. HYPOTHERMIA
• Coagulation factors are enzymes, their activity is substantially impaired by extremes of
temperature or pH.
• Hypothermia in vascular surgery can result from insufficient ambient temperature,
prolonged operative time, excessive blood loss, and the administration of cold fluid and
blood products.
• Maintenance of normothermia is critical during vascular procedures. Measures that should
be undertaken to prevent heat loss include ambient temperature control, the use of
warming blankets to cover the body except for the surgical field.
• Intravenous fluids and blood products can also be warmed with countercurrent warming
systems.
• Efforts to minimize the duration of the procedure and the extent of blood loss are also
effective.

49. ACIDOSIS
• It is well recognized that acidosis impairs normal coagulation. Studies have suggested that its major
inhibitory effect is on thrombin generation in the propagation phase of clotting, although the exact
mechanism has yet to be fully elucidated.
• A Ph decrease from 7.4 to 7.0 results in a reduction in factor VIIa activity by more than 90% and in
factor VIIa–tissue factor complex by more than 60%.
• In vascular surgery, acidosis is by following the reperfusion of large ischemic areas.
• The most effective treatment of coagulopathy related to acidosis is to identify and address the
underlying cause of the acidotic state.
• broad-spectrum antibiotics and aggressive drainage and/or débridement of infected tissue in sepsis.
• volume repletion and inotropic support in hypoperfusion.
• If reperfusion injury is anticipated, preemptive induction of respiratory and metabolic alkalosis prior to
arterial clamp removal can reduce resulting acidosis.

50. BLOOD/COAGULATION FACTOR REPLACEMENTS FOR ACHIEVING
HEMOSTASIS