1. Management of the Bleeding Patient
Dr. Alan Tinmouth
Director, Adult Regional Hemophilia and Bleeding Disorders Clinic
February 1st, 2005

2. Outline Review the mechanism of blood coagulation
Understand the tests used in the investigation of bleeding disorders
Understand the therapeutic options in the management of bleeding patients
“Hemostasis” Poker

3. Overview of Hemostasis

4. Primary Hemostasis: Platelets
Adhesion
Platelet glycoprotein Ib/V/IX adheres to subendothelium  binding is primarily to vWF
Activation
Shape change  formation of pseudopods
Anionic phospholipids (phospatidylserine and phosphoethanolamine) exposed on external membrane
Glycoprotein IIb/IIIa exposed on surface
Secretion of platelet granules
Aggregation
Platelets bind to each other via Gp IIb/IIIa receptor and soluble fibrinogen and vWF
 FORMATION OF HEMOSTATIC PLUG

5. Platelet Adhesion and Activation

6. Platelet Aggregation

7. Secondary Hemostasis: Coagulation Factors
Coagulation factors are proteins that circulate primarily in inactive state (proenzyme), which are converted to active enzyme
Activation of coagulation factors is a stepwise process of one activated factor activating subsequent factor(s)
Historically separated into the intrinsic pathway and extrinsic pathway
Intrinsic and extrinsic pathways believed to act independently and lead to formation of fibrin clot through separate “coagulation cascades”
Model fails to explain many coagulation abnormalities seen clinically

8. Coagulation in a test tube
XII
XIIa XI
XIa
VIIa
VII IX
IXa
+TF
INTRINSIC
EXTRINSIC
+VIIIa X Xa
+Va II
IIa
Fibrinogen
Fibrin
COMMON

9. Initiation Phase
Tissue factor is spark initiating coagulation cascade
Exposed TF activates factor VII
Factor VIIa:TF activates Factor VII*, Factor X*, Factor IX*
Factor Xa with Va generates a small amount of thrombin II
IIa X Xa TF
VIIa Va
TF-Bearing Cell TF
VIIa IX
IXa
* Vitamin K dependent clotting factors

10. Amplification Phase II
Factor VIIa:TF inactivated by Tissue Factor Pathway Inhibitor (TFPI):Factor Xa complex
Thrombin* (II) generated on TF-bearing cell activates platelets and coagulation factors (V, VII*, XI) II
IIa
VIII/vWF
TFPI Xa Xa TF
VIIa
VIIIa Va
TF-Bearing Cell XI
XIa V Va
Platelet
VIIIa Va
XIa
Activated Platelet
* Vitamin K dependent clotting factors

11. Propagation Phase II IIa
Activated platelets serve as phospholipid platform for generation of large amounts of thrombin
Factor IXa with VIIIa (+ Ca2+) [tenase] activates factor X
Factor Xa with Va (+ Ca2+) [pro-thrombinase] produces large thrombin burst
Thrombin then generates fibrin and fibrin clot
TF-Bearing Cell TF
VIIa IX II
IXa X Xa
IIa
IXa
VIIIa Va
XIa
Activated Platelet IX

12. Formation of Fibrin Clot: Fibrin Deposition
Thrombin binds to fibrinogen and forms fibrin
Cleaves fibrinopeptide A and B to leave fibrin monomer
Thrombin activates factor XIII to XIIIa,
Factor XIIIa catalyzes cross-linking of fibrin monomers to produce stable clot
IIa
IIa

13. Coagulation Factor Pathway in Vivo

14. Fibrinolysis Dissolution of clots needed to maintain vessel patency
Fibrin clots are temporary scaffolding that allow for cellular wound healing
Dissolution of clots needed to maintain vessel patency
Plasmin (converted from plasminogen) is primary agent of fibrinolysis
Fibrinolysis is controlled by
Activators of plasminogen activation
Inhibitors of plasminogen activation
Inhibitors of plasmin

15. Fibrinolysis and Plasmin Inhibition
Plasminogen and t-PA bind to fibrin lysine sites
Activated plasmin protected from degradation by alpha2-antiplasmin
Plasmin optimally positioned to degrade fibrin
Plasmin Inhibition
Circulating plasmin is rapidly inactivated by alpha2-antiplasmin
Prevents systemic (widespread) fibrinolysis
Thrombin activated fibrinolytic inhibitor (TAFI) removes lysine sites from fibrin to
downregulates fibrinolysis during initial clot formation

16. Fibrinolytic System

17. Laboratory Investigations

18. Platelet Disorders Platelet Count Platelet Morphology (blood film)
Platelet Aggregation / Release
von Willebrand Studies
von Willebrand Antigen
Ristocetin Cofactor
von Willebrand Multimers
Bleeding Time

19. Coagulation Factor Disorders
Prothrombin Time / International Normalized Ratio
Activated Partial Thromboplastin Time
Thrombin Time
50:50 Mixing Studies
Coagulation Factor Assays

20. Prothrombin Time / International Normalized Ratio
Tests for deficiencies or inhibitors of factor VII (a.k.a. extrinsic pathway)
Also deficiencies or inhibitors of fibrinogen, prothrombin, IX, X
Method
Tissue thromboplastin (tissue factor and phospholipid source) is added to recalcified citrated plasma  time to clot measured
Different sources of thromboplastin alter the PT  reported as an INR which adjusts for the different sensitivities of the thromboplastins
Other Specific Uses
Monitor warfarin (oral anticoagulant) therapy

21. Activated Partial Thromboplastin Time
XII
XIIa XI
XIa
VIIa
VII IX
IXa
+TF
INTRINSIC
EXTRINSIC
+VIIIa X Xa
+Va II
IIa
Fibrinogen
Fibrin
COMMON

22. Activated Partial Thromboplastin Time
Tests for deficiencies or inhibitors of factors VIII, IX, XI and XII (a.k.a. intrinsic pathway)
Reduced activity of fibrinogen, prothrombin or factor V or X prolongs the aPTT but the PT/INR is more sensitive
Method
Test initiated by recalcifying plasma that has incubated with an activator (eg. kaolin) and phospholipid  time to clot formation is measured
Other Specific Uses
monitor standard heparin therapy
screen for lupus anticoagulants / antiphospholipid antibodies

23. Activated Partial Thromboplastin Time
XII
XIIa XI
XIa
VIIa
VII IX
IXa
+TF
INTRINSIC
EXTRINSIC
+VIIIa X Xa
+Va II
IIa
Fibrinogen
Fibrin
COMMON

24. Thrombin Time (TT) Tests for deficiencies or dysfunction of fibrinogen
Prolonged in the presence of heparin, low or abnormal fibrinogen, and fibrinogen/fibrin degradation products
Method
Thrombin added to plasma and the time to clot (the rate of conversion of fibrinogen to fibrin) is measured
Uses
Detect low fibrinogen levels, abnormal fibrinogen or inhibitors of fibrin/fibrinogen

25. Thrombin Time (TT) XII XIIa XI XIa VIIa VII IX IXa X Xa II IIa
+TF
INTRINSIC
EXTRINSIC
+VIIIa X Xa
+Va II
IIa
Fibrinogen
Fibrin
COMMON

26. Fibrinolytic System Euglobulin Lysis Alpha 2 Antiplasmin
Factor XIII levels

27. Therapy

28. Platelet Transfusions - Products
Random Donor Platelets
Separated from whole blood donations
Dose = 5 units ( mls)
ABO matched preferable but not mandatory
Increases platelet ct by 5-10 x 109/L per unit
Single Donor Platelets
Collected from 1 donor by apheresis
Equivalent to 5-6 random donor platelets
Decrease donor exposure
Can be matched if patient has identified antibodies to platelets (alloimmune platelet refractoriness)

29. Indications for Platelet Transfusions
Thrombocytopenia
Platelet Dysfunction
Congenital
Acquired
Therapeutic
Plat ct < 50x109/L
Plat dysfunction
Prophylactic
Prior to invasive procedures
Plat ct < x109/L
Prevent spontaneous bleeding
Plat ct  10x109/L

30. Fresh Frozen Plasma Bleeding or Emergency procedure or operation
Made from whole blood within 8 hrs of collection
Contains all coagulation factors
Minimum factor VIII level of 0.7 IU/ml
mls / unit
Effect may only last 4 hrs (t1/2 of factor VII)
Indications:
INR / PTT > 1.5 x normal
and
Bleeding or
Emergency procedure or operation

31. Fresh Frozen Plasma Dose: 10-15 ml/kg for bleeding patients
Sufficient to increase all individual coagulation factors by 30% (minimum hemostatic level)
5-7 ml/kg may be sufficient for warfarin reversal
Alternatives
Vitamin K
2 mg will correct INR in hrs
No effect on PTT (factors VIII, IX, XI)
Oral dose more effective than subcutaneous
Intravenous associated with anaphylactic reactions

32. Cryoprecipitate Precipitate collected from plasma thawed at 40C
10-15 mls/unit
Contains specific clotting factors from plasma
Factor VIII
Fibrinogen
von Willebrand’s Factor
Factor XIII
Indications
Fibrinogen < 1.0 g/L
Dysfibrinogenemia

33. Cryoprecipitate Dose 1 unit / 5-10 kg body weight (total 8-10 units)
t ½ of 3-5 days
Alternatives
Factor VIII or IX Deficiency
recombinant factor VIII or IX
Von Willebrand’s Disease
virally inactivated plasma derived factor concentrates
Other factor deficiencies
recombinant factor concentrates

34. DDAVP Synthetic vasopressin Release of VIII and vWF from endothelium
May also help with platelet dysfunction
2-3 fold rise in levels
Dose – 0.3 ug/kg q hours
Tachyphylaxis may occur after 2-3 doses

35. Antifibrinolytics Tranexamic acid (Cyclokapron)
20-25 mg/kg po or 10 mg/kg IV q8h
Epsilon aminocaproic acid (Amicar)
50-60 mg/kg po q6h
Competitive inhibition with plaminogen activator (t-PA)
Prevents fibrinolysis (clot breakdown)
Promotes thrombosis
Relative contraindication in renal bleeding

36. Recombinant Factor VIIa
Initiates coagulation by interaction with TF
Only approved for treatment of hemophilia with inhibitors
Treat/prevent bleeding in other patient groups?
Efficacy not proven
Risk of thrombosis?
Primary use is bleeding patients refractory to other treatments
Dose for hemophilia 90 ug/kg q2-3h
Lower dose often effective in other patients ug/kg
Vials of 1.2 mg, 2.4mg, 4.8mg
Cost ~ $1000/mg

37. “Hemostasis” Poker

38. One-of-a-Kind INR aPTT TT/Fib Platelets Disorders  N N  N  N 
Liver disease
Vit K def
Coumadin
Factor VII N 
Heparin
Antiphospholipid Ab
Factor VIII, IX, XI
von Willebrand’s
(Factor XII) N 
Hypofibrinogenemia
Dysfibrinogenemia
Thrombin Inhibitors
Heparin N 
ITP
TTP/HUS
Drugs
Bone Marrow
Splenomegaly

39. Pair INR aPTT TT/Fib Platelets Disorders  N Factor II, V, X,
Coumadin Overdose

40. Three-of-a-Kind INR aPTT TT/Fib Platelets Disorders   N
Liver disease (acute)

41. Full House INR aPTT TT/Fib Platelets Disorders  
Liver disease (chronic)
DIC

42. Nothing Von Willebrand’s Disease Mild Hemophilia A or B
Mild Factor XI deficiency
Platelet Function Disorder
Factor XIII deficiency
Alpha 2 antiplasmin deficiency
Plasminogen Activator Inhibitor deficiency