General Articles Hematology

Haemostasis


Haemostasis

Mechanism : 1. Immediate response : Vasoconst. + plat. Plug.
2. Secondary : Fibrin deposition .

Stage 1 : Pre‐injury :
. Vascular endoth. Produce subs. Prevent adhesion of plat. & WBC to
vessel wall (NO2 , prostocyclin)

Stage 2 : Early Haemostasis :
. Plat. Adher. & coagulaltion activation → Thrombin

Stage 3 : Fibrin clot formation .

Stage 4 : Limiting clot formation by natural anticoagulants (antithrombin , TFPI
, protein C & S ).

Stage 5 : Fibrinolysis . Plasmin degrades fibrin → vessel recanalisation & tissue
repair .

Clotting Factors : Half life
I. Fibrinogen 4‐5 days
II. Thrombin 3 days
III. Tissue F. —-
IV. Ca++ —-
V. Labile F. 12-13 h
VI. No longer used —-
VII. Proconvertin 4-7 h
VIII. AHF 8-10 h
IX. Christmas F 1 day
X. Stuart power F 2 days
XI. Plasma Thromboplastin antecedent 2-3 days
XII. Hagman F 1 day
XIII. Fibrin stabilisig F. 8 days

All produce by the liver , FV also by plat. & endoth. Cells .
VIT. K dependent factors II VII IX X (inhibited by WARFARIN)



Blood Coagulation :

1. Extrinsic pathway : initiated by F VII interacting with Tissue Factor.
2. Intrinsic pathway : initiated after exposure of subendoth. Collagen after vessel
damage . XII XI IX VIII

Definition of hemostasis

Platelets :

. Formed in Bone marrow from Megakaryocytes.
. Thrombopoiten (liver) stimulate formation & Maturation of plat.
. Circulate in Bl. For 8‐10 days before destroyed in RES.
. 30% pooled in spleen.
. Discoid 2‐4 Mm diameter.
. Invaginated surface Memb. to form Canaliculi.

Screening tests for bleeding disorders:

1. Plat. Count (normal = 150‐400 X 109 /L
2. Bleeding time (normal < 8 min.) prolonged in thrombocytopenia, abn. Plat. F, VWD,
vasc. & con. T dis.
3. Prothrombin time (PT) : assess extrinsic pathway (normal 9‐12 s). F II, V, VII, X
4. Partial thromboplastin time (PTT) : assess intrinsic pathway (normal 26‐36 s). F II, V,
VIII, IX, X, XI, XII, sever fibrinogen def. heparin, inhibitors
5. Prolonged PT & PTT = common pathway (X, V, II & I) , or > one factor def.
6. Fibrinogen conc. (normal 1.5‐4 g/L) hypofibr. e.g. liver dis. DIC.
7. Mixing tests with normal plasma differentiate between coag. Factor def. &
presence of inhibitors (the prolonged time does not correct).
8. plat. Functions tests.

Bleeding Disorders : suspect if
  1.  Multiple sites
  2. Spontaneous
  3.  Prolonged

1. Vascular purpura

  • a. Hereditary : Defective collagen .
  • b. Acquired : Immune, Inflammatory .

2. Platelets defects : Quantity, Quality

3. Coagulation defects :

  • Reduced synthesis of Fs
  • Abnormal Fs
  • Destruction (DIC)
  • Inhibitors

4. Fibrinolytic defects :

  • e.g. Excessive fibrinolysis following therepeutic thrombolysis.
Clinical assessment

1. Site of bleeding

  • Ms, Joints, Retrop , indicate coagulation defect.
    Purpura, Epistaxis, G.I.T., Menorrhagia, indicate low plat, plat. F. defect,
    WWD.
  • Recurrent in single site – local abn.

2. Duration : Acq. Or Cong.

3. Precipitating Fs : Spont. , or traumatic.

4. Surgery, Exo, Tonsilectomy, Circumcision.

Immediate : Pri. Haemostasis
Delayed : Coag. def.

5. F.H. : Absence does not exclude hereditary dis.

6. Drugs .

Differentiation bet. Plat. dis & Coagul. dis
Plat dis. Coagul. dis.
Sex F > M M > F
Age 20‐40 y childhood
Onset Immediate Delayed
Type Mucocut Deep Ts.
Local pr. Effective Not
Ex. ITP Haemophilia
Causes of thrombocytopenia :
  • 1. Reduced production : Bone marrow dis.
    Aplastic Anaemia, Leukemia, Cytotexics
    B12 Folic ac. def.
  • 2. Increased Consumption :
    ITP , DIC, TTP .
Non Thrombocytopenic purpura
  • 1. Senile
  • 2. Factitious
  • 3. H. S. P.
  • 4. Vasculitis
  • 5. Paraproteinaemia
  • 6. Steroids .
Idiopathic Thrombocytopenic Purpura (ITP)
  • Aetiology : Auto Abs against plat. gy g p Memb. Glucoprotein Ilb / IIIa leads to
    premature removal by RES. May be assoc. with CTD, HIV, Pregnancy,
    Drugs.
  • Clinical : Depends on degree of thrombocytopenia.
    Spont. Bl. < 20 X 109 / L
    < 10 X 109 / L – Risk of I.C. Bleeding
    Higher count : Easy Bruising. Epistaxis, Menorrhagia
    > 50 X 109 / L – accidental.
    F > M
    Preceeding Viral inf. – unusual.
    CTD at presentation or later
    Splenomegally – Unusual.
  • Lab. : BI. Film – reduced plat.
    B. M. – Incr. or normal Megakaryocytes.
    Plat. Abs ‐ positive
  • D.D. : Acute leulcemia, Apl. An., DIC, SLE.
Management of ITP :
  • . Stable, plat > 30 X 109 / L 10 – No treatment, except with Surgery or Biopsy
  • . Spont. Bleeding – Prednisolone 1 mg / kg / day ( suppress Ab. Prod. and
    inhibit phago. ) count will increase to normal or less in 2‐4 weeks, then reduce
    does gradually.
  • . Relapse – Reintroduce Steroids
  • . Immunoglobulin i.v. (Block Ab receptor on RES) + steroids in severe
    haemostatic Failure
  • . Anti‐D i.v. (Bind RBC and saturate Ab. Receptors in Rh + ve (+ spleen)
  • . Persistent or life threatening Bleeding needs plat. Transfusion
  • . 2 Relapses or Pri. Refractory needs splenectomy.
    70% complete remission.
    20‐25% ‐ improvement
    5‐10% require further treat. e.g. low dose steroids, Immunosup. (Rituximab,
    Ciclosporin)

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