08 Hemostasis

HEMOSTASIS

By Prof\ Sameh ShamaaProf Of medical Oncology and

Internal medicine Mansoura Faculty Of Medicine

HEMOSTASIS

HEMOSTASIS

Def:- stoppage of bleeding from the blood vessels

Mechanisms (I) v.c of blood vessels (II) platelet plug formation (III) Blood coagulation (fibrinogen fibrin)(IV) Clot retraction (V) fibrinolysis to dissolve the clot

HEMOSTASIS

PRIMARY HEMOSTASIS

includes the processes that result in the formation of the platelet plug.

Necessary factors:--The blood vessels : the vessel walls esp. the

subendothelial layer.

-The platelets

-2 plasma glycoproteins :

- fibrinogen

- Willebrand factor ,which also presents inside the platelets

Mechanisms:

1-v.c of the bl. vessel.

2 -Platelets adhesion to subendothelial layer, ( Willebrand factor is necessary for this stage)

adhesion of platelets- 3- platelets secretion:

their activation and secretion of ADP,adrenaline, noradrenaline –> aggregation & activation of other platelets.

4 -Aggregation of platelets.

5 -Formation of capillary plug.

HEMOSTASIS

Exploration of the 1ry homeostasis

1) Important points in the history of any bleeding patients :

HEMOSTASIS

- Family history

- Duration (recent onset or since childhood)

- Duration of the bleeding episode.

- Circumstance of bleeding

(spontaneous, after trauma, or surgery)

HEMOSTASIS

Type and character of bleeding :-- Purpuric spots

(capillary or platelets defect not characteristic of hemophilia)

- Hematoma, hemarthrosis or large ecchymoses at the site of trauma :suggests hemophilia (coagulation defect)

- Sudden severe bleeding from multiple sites after prolonged surgery or during obstetric procedures suggests acquired fibrinogen defect

HEMOSTASIS

2) Investigations :

HEMOSTASIS

1) Capillary resistance test of Hess

2) Platelets count

3) Bleeding time

time needed for the platelet plug formation

If . N. ------ Normal 1ry homeostasis .

↑ ------ platelet or vascular defect.

HEMOSTASIS

Capillary resistance test of Hess :

sphygmomanometer cuff above the cubital fossa and raise the pressure to 100 mm Hg (or midway between systolic & diastolic if systolic pressure <100) for 5 - 7' minutes- deflation '3 minutes later count the number of petichea in area of 3 cm diameter, 1 cm below the cubital fossa Normally up 10 if more than 20, means platelets or capillary wall defect

HEMOSTASIS

4) Other tests only done if there is a prolonged bleeding

time with normal platelet count - Measurement of capillary resistance - Measurement of Willebrand factor - Platelets function tests (Adhesiveness,

Aggregation)- other tests for platelets (clot retraction, ↓

prothrombin consumption).

HEMOSTASIS

Coagulation of Blood

Def :- represent the conversion of fibrinogen (soluble protein) to fibrin (insoluble) meshwork which occludes the point or vessel rupture.

HEMOSTASIS

First Step :Activation of factor X

BY One of 2 systems:

I-urgent system II-delayed system(Extrinsic system.) (Intrinsic system.)

HEMOSTASIS

systems of coagulation I-urgent system. II-delayed systemExtrinsic system. Intrinsic system.12-20'' (seconds) 4-8' (minutes)In vivo only. In vivo & in vitroDue to tissue damage. due to contact with foreign surface

↓ ↓ Tissue factor activation of contact system ↓ ↓

X < ------------------------------------IX a < ---------------- IX↓Xa↓

2- prothrombin thrombin

3-fibrinogen Fibrin

HEMOSTASIS

EXTRINSIC SYSTEM

FACTORS NICESSORY ARE:Factor XTissue factor and Factor VII

Tissue F.

VIIa VII Xa X

Blood vessel

HEMOSTASIS

INTRINSIC SYSTEM

Necessary factors: - XII (Hageman factor)

- Contact system XI Kallikrene kininogene

- F. IX- F. VIII - F. X- Ca. ++- phospholipids of the platelet’s membrane

HEMOSTASIS

Contact System: Foreign surface

|--------------------------------------------------| Kalierne XII kininogene

Fragmentation XIIa

XI XIa

Rest of intrinsic pathway

IX

HEMOSTASIS

Rest of intrinsic pathway IX

Platelets Ca ++

IXa

X VIIIa

VIIIXa

II IIa

HEMOSTASIS

Second Step: of Coagulation

Thrombin Formation: (IIa)

Factors needed:

- prothrombin (II) Ca++ platelets - Xa II V Ca++

- V (acceleririe) Xa

- phospholipids - Ca + + IIa

HEMOSTASIS

3rd Step :Fibrin Formation

Fibrin Formation:-------------------------

IIa XIII XIIIa

(Fibrinogen) -------------------- Ia (Soluble fibrin)

Insoluble Fibrin

HEMOSTASIS

Physiological anticoagulants

• 1- Serine protease inhibitors :inhibit the coagulation cascade.

• 2-Neutralizers of activated coagulation factors (components of protein C system)

HEMOSTASIS

1-Serine protease inhibitors:

• 1-Antithrombin (III).

• 2-Heparin and heparin like substance.

• 3-Alpha 1 antitypsin.

• 4-Alpha 2 macroglobulin

HEMOSTASIS

2-Neutralizers of activated coagulation factors :

(components of protein C system)

• 1-Protein C: synthesized in the liver, vit. K dependant, activated by thrombin.

• 2-Thrombomodulin.• 3-Protein S and C4b-binding protein.

HEMOSTASIS

Fibrinolysis

is the process wherein a fibrin clot, the product of coagulation, is broken down.Its main enzyme plasmin cuts the fibrin mesh at various places, leading to the production of circulating fragments that are cleared by other proteases or by the kidney and liver

HEMOSTASIS

HEMOSTASIS

Measurement

When plasmin breaks down fibrin, a number of soluble parts are produced. These are called fibrin degradation products (FDPs). FDPs compete with thrombin, and so slow down the conversion of fibrinogen to fibrin (and thus slows down clot formation).

Exploration of the coagulation

(I) whole blood clotting time

Normally 4-10 minutes

Generally ---> N. in platelets defects.

↑ = coagulation defect

But not very sensitive: - only +ve when blood coagulation is very defective

HEMOSTASISHEMOSTA fibrinolysis (Hyperfibrinolysis), SIS

(2) One stage prothrombin time:

general exploration or the extrinsic pathway (Quick time)

N : 16-18 sec.

•addition of tissue thromboplastin+

•ca++ to decalcified plasma ---> measure the time till coagulation occur.

• Affected by factors VII, X, V, II & fiboinogen (only severe defect)

HEMOSTASIS

(3) partial thromboplastin time (PTT)

or CKT(cephaline koalin time)

General exploration of the intrinsic pathway

clotting time of recalcified plasma in the presence of phospholipid (cephaline), while koalin powder for activation of Hageman factor'. Affected by factors XII, XI, IX, VIII, X, II

HEMOSTASIS

(4) Thrombin time

detect the defects in the conversion of fibrinogen ---> fibrin

Measured by addition of thrombin to citrated patients plasma

If polonged • Abnormalities of fibornogen

(hypo or hyper or dysfibrinogenemia)• Heparin• Presence of some abnormal proteinswhich inhibits the

polymerisation of monomers of fibrin. (e.g myeloma protein•

HEMOSTASIS

(5) Deficiency of F XIII (fibrin stabilizing factor ) detected by noting the solubility of fibrin in 5M urea or 1% monochloroacetic acid (can't dissolve fibrin in the presence of factor XIII).In congenital defect of f. XIII ---> dissolution of the clot in <10.

(6) Assay for each cogulation factor is available

HEMOSTASIS

(7) Detection of coagulation inhibitors:

1-Inhibitors for a specific factor (especially F. VIII) usually ---> severe hemorrhage2-Inhibitors against platelets or tissue

phospholipids ---> prolongation of tests of coagulation (Quick or CKT) e.g L.E

but usually no hemorrhagic manifestations3- if there is ↑of Quick test or CKT or thrombine:-50% of normal plasma + 50% of patient plasma(incubation at 370c for I hour) repeat the test If become normal ---> factor defectif no correction ---> presence of inhibitors.

HEMOSTASIS

PRACTICAL INVESTIGATION OF HEMOSTATIC TROUBLE

B.T

Platelets count

Quick test

CKT

Thrombin time

Dosage of fibrinogen

HEMOSTASIS

PRACTICAL INVESTIGATION OF HEMOSTATIC TROUBLE

I- B.T↑, platelets ↓( ↓80.000; mm3)

Thrombocytopenia

2- B.T↑, platelets normal

Qualitative platelets abnormalities Willebrand diseasecongenital or acquired

platelet factor tests dosage of factor VIII

HEMOSTASIS

PRACTICAL INVESTIGATION OF HEMOSTATIC TROUBLE

3- ↑Quick + ↑CKT Other tests are N

Acquired defect of several defect of factor common for factors (II, VII, X,V) 2 pathways ex. X or V or

II

4- Quick N., ↑ CKT: either:I- Hemophilia Aor B.2- Rarely ---> defect of one factor of the contact system

(XII, or XI or others)

HEMOSTASIS

PRACTICAL INVESTIGATION OF HEMOSTATIC TROUBLE

5- Quick ↑, CKT N

isolated defect of factor VII

in 3, 4..5 dosage of the factors with suspected deficiency, also search for inhibitors. Ex:

- ↑ Quick, normal dosage of factors---> hyperfibriongenemia which inhibit the test

- ↑Quick +↑CKT + no F. defect --->? Inhibitors, e.g. antiphospholipides.

HEMOSTASIS

PRACTICAL INVESTIGATION OF HEMOSTATIC TROUBLE

6-↑T.T either:* heparine in the blood or in the tube. Here T.T

can be corrected by adding eithera-toluidine blueb-Reptilase time (incomplete thrombin not

sensitive to heparin and not inhibited by antithrombin III).

* If (a-b also defective) ---> troubles of fibrin polymerisation :either due to abnormal fibrin (dysfibrinogenimia) or inhibition e.g by ---> myeloma protein or F.D.P.

HEMOSTASIS

PRACTICAL INVESTIGATION OF HEMOSTATIC TROUBLE

7- ↓fibrinogen * congenital afibrinogenimia or

hypofibrinogenimia• Acquired hypofibrinogenimia e.g.liver

cirrhosis.• consumption of fibrinogen: e.g. D.I.V.C,

fibrinolysis

HEMOSTASIS

8-All tests ate Normal:

* Capillary fragility (usually only ecchymoses ) ---> measurement of cap.fragility.

* deficient factor XIII

* no hemostatic troubles.

PRACTICAL INVESTIGATION OF HEMOSTATIC TROUBLE

HEMOSTASIS

Thank You

HEMOSTASIS