Agents dynamics

DIC is an acquired thrombohemorrhagic disorder that results from the effects of excessive formation of thrombin and plasmin in circulation.

DIC is always secondary to an underlying pathologic process that triggers activation of blood and generation of thrombin.

The causes of DIC are:

1. Intravascular hemolysis 2. Infection

a. Septicemia purpura fulminans

b. Postsplenectomy sepsis, meningococcemia (Gram negative) 3. Obstetric complications

4. Burns, electric shock and 1. Shock (from any cause) 5. Heat stroke

6. Fat embolism

7. Surgery- cardiac bypass surgery, lung, brain 8. Envenomation

9. Malignancies- AML, prostatic, GIT 10. Pancreatitis

11. LeVeen shunts

12. Vascular disorders: hemangiomas, vasculitis

DIC is characterized by the consumption of clotting factors and platelets within the circulation, resulting in varying degrees of microvascular obstruction.

When significant platelet and coagulation factor consumption occurs, bleeding becomes a major feature.

A secondary fibrinolysis occurs, which in some cases, may accentuate the bleeding:

These events may lead to:

1. Tissue ischemia and necrosis 2. Generalized hemorrhgic state 3. Hemolytic anemia

A wide spread activation of the coagulation system, with consumption of clotting factors occurs with the following results:

1. Reduction of the circulating clotting factors and platelets

"consumption"

2. Blood becomes incoagulable, and severe bleeding manifestations may occur.

3. Thrombosis in the small blood vessels, which leads to tissue ischemia, infarction and Necrosis.

4. Hemolytic anemia of the microangiopathic type, with prominent fragmented RBCs ―Schistocytes in the blood smear".

Clinical Features

Some patients are asymptomatic with only laboratory evidence of DIC.

Symptoms and signs due to DIC:

a). Hemorrhagic manifestations which vary in severity.

(b). Tissue thrombosis may involve many organs and infarctions of large areas of skin and subcutaneous tissue, or of kidneys.

(c). Microangiopathic hemolytic anemia; due to red cell distortion and fragmentation in small blood vessels.

(d). Renal and adrenal failure may occur, due to intravascular thrombosis.

Laboratory Finding Prolonged TT, PT, PTT

Hypofibrinogenemia, thrombocytopenia and low factor VIII

Fibrin split products (FSP) appear in the blood, due to activation of fibrinolysis.

Blood smear show fragmented RBCs, schistocytes. These changes are referred

as microangiopathic hemolytic anemia.

Treatment

1. Treat the cause, e.g antibiotic, removal of the procoagulant stimulus (e.g a dead fetus).

2. Supportive therapy with fresh frozen plasma, platelet concentrates and cryoprecipitate if bleeding is dominant

3. Anticoagulant therapy (e.g heparin) if thrombosis is dominant.

4. Protein C and antithrombin in selected patients.

Thrombosis

Thrombosis may occue in either the arterial or venous circulation. It is the pathological process whereby platelets and fibrin interact with vessel wall to form a hemostatic plug to cause vascular obstruction (Virchow’s triad).

Virchow’s Triad 1. Stasis

2. Hypercoagulable state 3. Endothelial plug Mechanisms

A. Endothelial damage B. Blood flow

1. Stasis 2. Turbulence 3. Hyperviscosity C. Blood components

1. Platelets 2. Thrombin 3. Factor VIII

4. Fibrin (dysfibrinogenemia) 5. Plasminogen activator deficiency

D. Hypercoagulability

1. Malignant disease 2. Oral contraceptive 3. Pregnancy 4. Postoperative or prolonged recumbency 5. DIC 6. Lipid 7. Antithrombin III deficiency 8. Protein S and C deficiency

Therapy and Prophylaxis 1. Anticoagulants

 Low molecular weight heparin: In this type of heparin decreased incidence of heparin induced thrombcytopenia and no test required.

 Unfractionated heparin- maintains PTT 1.5-2.5 X the normal control.

 Coumadin (Warfarin) 2. Thrombolytics

 Plaminogen activators

 Snake venom enzymes (ancrod) 3. Antiplatelet agents

 ASA

 Sulfinopyrazone



Dipyridamole

REVIEW QUESTIONS

1. Factor I is commonly known as a. Tissue factor

b. Prothrombin

c. Antihemeophilic factor d. Fibrinogen

2. The traditional intrinsic coagulation pathway includes factors a. X, V, IV, III, II and I

b. XII, XI, IX, VIII, Prekallikerin and HMWK c. XII, X, IX, XIII, Prekallikerin and HMWK d. VII and tissue factors

3. A substance released from platelets that promotes their aggregation is a. HMWK

b. ADP c. Factor V d. 2-atntiplasmin

4. Epistaxis is mean a. Nose bleed

b. Vomiting of blood

c. Excessive menstrual bleeding d. Blood in the urine

5. A normal hemostatic mechanism depends upon the normal structure and function of

a. Tissue surrounding the blood vessels b. Platelets

c. Blood vessels

d. Plasma coagulation protein e. All of the above

6. The coagulation factors that are vitamin K dependent are:

a. I, V, VIII an XIII b. II, VII, IX, and X c. XII, XI, Prekallikerin d. II, VII, IX and XI

7. Thrombin has many roles in hemostasis a. Activation of factor XIII

b. Activation of protein C

c. Conversion of fibrinogen to fibrin

d. Both enhancing and inhibiting coagulation e. All of the above

8. Antithrombin III inhibits a. Factors IIa, IXa, and Xa b. Plasmin

c. Factors XIA and XIIa d. Kallikerin

e. All of the above

9. The Prothrombin time test

a. It is the most frequently used test to monitor anticoagulant therapy with Vitamin K antagonists

b. It is a good screen for the intrinsic and common pathways.

c. It is reported as a percentage of factor activity d. All of the above

10. The Thrombin time test will be prolonged by all of the following except:

a. Dysfibrinogenemia b. Fibrin Split Products c. Elevated fibrinogen levels d. Heparin

11. The international normalized ratio (INR) is useful for a. Determining coagulation reference ranges

b. Monitoring heparin therapy c. Monitoring thrombotic therapy d. Monitoring warfarin therapy

12. The international normalized ratio (INR) is used to correct for differences in reagent preparations for

a. Prothrombin time

b. Partial Thromboplastin Time c. Activated Clotting Time d. Lee-White Clotting time.

13. Which of the following is NOT a vitamin K dependent factor?

a. Factor V b. Factor VII c. Prothrombin d. Factor IX e. Factor X

14. Which vitamin K dependent clotting factor has the shortest half-life?

A. Prothrombin B. Factor VII C. Factor IX D. Factor XI

In document Formation and organisation in robot swarms (Page 93-104)