Transcript Liver disease, vitamin K deficiency, warfarin, DIC

Biochemistry of Coagulation
Ahmad Shihada Silmi Msc, FIBMS
Staff Specialist in Hematology
Medical Technology Department
Islamic University of Gaza
2012
The Protein C Anticoagulant Pathway
Blood Flow
Protein C
Thrombin
Thrombin
APC
Thrombomodulin
Thrombus
Thrombus
at site of injury
Anticoagulation
downstream
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The Protein C Anticoagulant Pathway
Blood Flow
Vai
Factor V Leiden
VIIIai
VIIIa
Va
APC
PS
APC
PS
Thrombus
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Proposed Mechanism of AT III-Heparin
System
Lysine
sites
AT III
Serine site
Thrombin
Antithrombin
III
H
Th
Arginine
site
Heparin
H
AT III
Th
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Fibrinolytic Pathway
Fibrinolysis is initiated when fibrin is formed
and eventually dissolves the clot.
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Fibrinolytic Pathway
PAI-1
Plasminogen
Tissue Plasminogen Activator (t-PA)
Urokinase (uPA)
Plasmin Inhibitor
Exogenous: streptokinase
XL-Fibrin, fibrinogen
Plasmin
XL- fibrin
degradation products (FDP)
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Degradation of Fibrin/Fibrinogen
Fibrinogen or Fibrin
Plasmin
Fragment X
Small Peptides
Plasmin
Fragment Y
Fragment D
Small Peptides
Plasmin
Fragment E
Fragment D
Small Peptides
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Approach to evaluate
Fibrinolysis
D-Dimer, a measure of fibrin degradation
products, is the final product formed
during the fibrinolysis process by
plasmin
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Approach to evaluate Fibrinolysis cont,
– Elevated levels of D-Dimer are indicative of
on-going fibrinolysis
• Found high in :
• (DVT)
• (PE)
• (DIC)
• D-Dimer levels also rise during the normal
pregnancy and very high levels are
associated with complications.
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Bleeding Disorders
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Clinical Features of Bleeding Disorders
Platelet disorders
Site of bleeding
Petechiae
Ecchymoses (“bruises”)
Hemarthrosis / muscle bleeding
Bleeding after cuts & scratches
Bleeding after surgery or trauma
Coagulation factor
disorders
Skin
Mucous membranes
(epistaxis, gum,
vaginal, GI tract)
Yes
Small, superficial
Extremely rare
Yes
Immediate,
usually mild
Deep in soft tissues
(joints, muscles)
No
Large, deep
Common
No
Delayed (1-2 days),
often severe
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Hematologic disorders causing
bleeding
– Coagulation factor disorders
–Platelet disorders
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Coagulation factor disorders
 Inherited
bleeding
disorders
– Hemophilia A and B
– Von Willebrands
disease
– Other factor
deficiencies

Acquired bleeding
disorders
– Liver disease
– Vitamin K
deficiency/warfarin
overdose
– DIC
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Hemophilia A and B
Coagulation factor deficiency
Inheritance
Incidence
Severity
Complications
Hemophilia A
Hemophilia B
Factor VIII
Factor IX
X-linked
recessive
X-linked
recessive
1/10,000 males
1/50,000 males
Related to factor level
<1% - Severe - spontaneous bleeding
1-5% - Moderate - bleeding with mild injury
5-25% - Mild - bleeding with surgery or trauma
Soft tissue bleeding
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Hemophilia
Clinical manifestations (hemophilia A & B are
indistinguishable)
Hemarthrosis (most common)
Fixed joints
Soft tissue hematomas (e.g., muscle)
Muscle atrophy
Shortened tendons
Other sites of bleeding
Urinary tract
CNS, neck (may be life-threatening)
Prolonged bleeding after surgery or dental extractions
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Hemarthrosis (acute)
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von Willebrand Disease: Clinical Features
 von
–
–
–
–
–
Willebrand factor
Synthesis in endothelium and megakaryocytes
Forms large multimer
Carrier of factor VIII
Anchors platelets to subendothelium
Bridge between platelets
 Inheritance
 Incidence
 Clinical
- autosomal dominant
- 1/10,000
features - mucocutaneous bleeding
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Laboratory evaluation of von Willebrand disease


Classification
– Type 1
Partial quantitative deficiency
– Type 2
Qualitative deficiency
– Type 3
Total quantitative deficiency
Diagnostic tests:
Assay
1
vonWillebrand type
2
3
___________________________________________________
vWF antigen
vWF activity
Multimer analysis


Normal
Normal

Normal


Absent
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Vitamin K deficiency

Source of vitamin K
Green vegetables
Synthesized by intestinal flora

Required for synthesis
Factors II, VII, IX ,X,Protein C and S

Causes of deficiency
Malnutrition
Biliary obstruction
Malabsorption
Antibiotic therapy

Treatment
Vitamin K
Fresh frozen plasma
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Common clinical conditions associated with
Disseminated Intravascular Coagulation
• Activation of both coagulation and fibrinolysis
Triggered by
• Sepsis
• Trauma
– Head injury
– Fat embolism
• Malignancy
• Obstetrical complications
– Amniotic fluid embolism
– Abruptio placentae
• Vascular disorders
• Reaction to toxin (e.g.
snake venom, drugs)
• Immunologic disorders
– Severe allergic reaction
– Transplant rejection
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Disseminated Intravascular Coagulation
(DIC) Mechanism
Systemic activation
of coagulation
Intravascular
deposition of fibrin
Thrombosis of small
and midsize vessels
with organ failure
Depletion of platelets
and coagulation factors
Bleeding
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Pathogenesis of DIC
Release of
thromboplastic
material into
circulation
Coagulation
Fibrinolysis
Fibrinogen
Plasmin
Thrombin
Fibrin
Monomers
Fibrin
Clot
(intravascular)
Consumption of
coagulation factors;
presence of FDPs
 aPTT
 PT
 TT
 Fibrinogen
Presence of plasmin
 FDP
Fibrin(ogen)
Degradation
Products
Intravascular clot
 Platelets
Schistocytes
Plasmin
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Classification of platelet disorders
• Quantitative disorders
– Abnormal distribution
– Dilution effect
– Decreased production
– Increased destruction
• Qualitative disorders
– Inherited disorders
(rare)
– Acquired disorders
• Medications
• Chronic renal failure
• Cardiopulmonary
bypass
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Laboratory Evaluation of Bleeding
Overview
CBC and smear
Platelet count
RBC and platelet morphology
Thrombocytopenia
TTP, DIC, etc.
Coagulation
Prothrombin time
Partial thromboplastin time
Coagulation factor assays
50:50 mix
Fibrinogen assay
Thrombin time
fibrinogen defects
FDPs or D-dimer
Extrinsic/common pathways
Intrinsic/common pathways
Specific factor deficiencies
Inhibitors (e.g., antibodies)
Decreased fibrinogen
Qualitative/quantitative
von Willebrand factor
Bleeding time
Platelet function analyzer (PFA)
Platelet function tests
vWD
In vivo test (non-specific)
Qualitative platelet disorders and vWD
Qualitative platelet disorders
Platelet function
Fibrinolysis (DIC)
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Laboratory Evaluation of the
Coagulation Pathways
Partial thromboplastin time
(PTT)
Prothrombin time
(PT)
Surface activating agent
(Ellagic acid, kaolin)
Phospholipid
Calcium
Thromboplastin
Tissue factor
Phospholipid
Calcium
Intrinsic pathway
Extrinsic pathway
Thrombin time
Common pathway
Thrombin
Fibrin clot
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Pre-analytic errors

Problems with blue-top
tube

– Hct ≥55 or ≤15
– Lipemia,
hyperbilirubinemia,
hemolysis
– Partial fill tubes
– Vacuum leak and citrate
evaporation

Problems with
phlebotomy
–
–
–
–
–
Heparin contamination
Wrong label
Slow fill
Underfill
Vigorous shaking
Biological effects

Laboratory errors
– Delay in testing
– Prolonged incubation at
37°C
– Freeze/thaw deterioration
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Initial Evaluation of a Bleeding Patient - 1
Normal PT
Normal PTT
Urea
solubility
Abnormal
Factor XIII deficiency
Normal
Consider evaluating for:
Mild factor deficiency
Abnormal fibrinolysis
(a2 anti-plasmin def)
Elevated FDPs
Monoclonal gammopathy
Platelet disorder
Vascular disorder
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Initial Evaluation of a Bleeding Patient - 2
Normal PT
Abnormal PTT
Repeat
with
50:50
mix
50:50 mix is
abnormal
Test for inhibitor activity:
Specific factors: VIII,IX, XI
Non-specific (anti-phospholipid
Ab)
50:50 mix is normal
Test for factor deficiency:
Isolated deficiency in intrinsic pathway (factors VIII, IX, XI)
Multiple factor deficiencies (rare)
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Initial Evaluation of a Bleeding Patient - 3
Abnormal PT
Normal PTT
Repeat
with
50:50
mix
50:50 mix is
abnormal
Test for inhibitor activity:
Specific: Factor VII (rare)
Non-specific: Anti-phospholipid (rare)
50:50 mix is normal
Test for factor deficiency:
Isolated deficiency of factor VII (rare)
Multiple factor deficiencies (common)
(Liver disease, vitamin K deficiency, warfarin, DIC)
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Initial Evaluation of a Bleeding Patient - 4
Abnormal PT
Abnormal PTT
Repeat
with
50:50
mix
50:50 mix is
abnormal
Test for inhibitor activity:
Specific : Factors V, X, Prothrombin,
fibrinogen (rare)
Non-specific: anti-phospholipid (common)
50:50 mix is normal
Test for factor deficiency:
Isolated deficiency in common pathway: Factors V, X,
Prothrombin, Fibrinogen
Multiple factor deficiencies (common)
(Liver disease, vitamin K deficiency, warfarin, DIC)
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Coagulation factor deficiencies
Summary
Sex-linked recessive
 Factors VIII and IX deficiencies cause bleeding
Prolonged PTT; PT normal
Autosomal recessive (rare)
 Factors II, V, VII, X, XI, fibrinogen deficiencies cause bleeding
Prolonged PT and/or PTT
 Factor XIII deficiency is associated with bleeding and
impaired wound healing
PT/ PTT normal; clot solubility abnormal
 Factor XII, prekallikrein, HMWK deficiencies
do not cause bleeding
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Thrombin Time
 Bypasses
factors II-XII
 Measures
rate of fibrinogen conversion to fibrin
 Procedure:
– Add thrombin with patient plasma
– Measure time to clot
 Variables:
– Source and quantity of thrombin
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Causes of prolonged Thrombin Time
 Heparin
 Hypofibrinogenemia
 Dysfibrinogenemia
 Elevated
FDPs or paraprotein
 Thrombin inhibitors (Hirudin)
 Thrombin antibodies
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Approach to the thrombocytopenic
patient

History
– Is the patient bleeding?
– Are there symptoms of a secondary illness? (neoplasm,
infection, autoimmune disease)
– Is there a history of medications, alcohol use, or recent
transfusion?
– Are there risk factors for HIV infection?
– Is there a family history of thrombocytopenia?
– Do the sites of bleeding suggest a platelet defect?

Assess the number and function of platelets
– CBC with peripheral smear
– Bleeding time or platelet aggregation study
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Bleeding time and bleeding
 5-10%
of patients have a prolonged bleeding
time
 Most
of the prolonged bleeding times are due to
aspirin or drug ingestion
 Prolonged
bleeding time does not predict excess
surgical blood loss
 Not
recommended for routine testing in
preoperative patients
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Conclusion
Special Coagulation is a specialized,
complex and dynamic field!
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