HEPARIN - LITERATURE REVIEW

Heparin, is a natural anticoagulant in the body found in the liver (from the Greek word” hepar” meaning  liver)  and may also  be within basophils and mast cells. Heparin is also called anti thromboplastin or antithrombin (Schalms;  2006)  Heparin is isolated from either porcine intestine or form beef  lung where it is bound to histamine and stored in the mast cell granules, when heparin is  isolated, the  purification leads to a heterogeneous mixture of molecules it is an acidic polysaccharide with side groups, either  sulpates or N-acetyl  groups  attached to
individuals  sugar  group. The sulfate groups are extremely important in the anticoagulant activity by binding to antithrombin III (at III) enhancing the rate of thrombin –Antithrombin III complex formation by 1,000 to 10,000 fold. (platelet inhibitors, com/review article).  
Heparin is available in a liquid or dry form as sodium, calcium, ammonium and lithium salts, each of these will interfere with determination of their   respective ions in the plasma.

Mode of action; it interferes with the formation and / or activity of
thrombin and the activity of clotting factors IX, X, XI, XII. (Schalms; 2006).
Lithium or sodium  salt   of pheparin at a concentration  of  10  20ul per ml of blood is a commonly used anticoagulant for chemistry, gas analysis and emergency tests. It does not alter the size of the red cells, and it is recommended when it is important to reduce to a minimum the chance of  lysis  occurring after blood has been drawn. It is thus the best anticoagulant for osmotic fragility test and is suitable for immuniphenotyping (Dacie and Lewis; 2008).
However, heparin is not suitable for blood counts because it often induces platelet and leucocyte clumping (Van and Simmons; 1995, Salzamin and Rosenberg; 1980, and Hirsh and Levine; 1992).

Disadvantages of Heparin Anticoagulant,
1.      It causes clumping of leucocytes
2.      It interferes with the staining of leucocytes
3.      It is the most expensive of anticoagulants
4.      Blood will clot within  8-12  hours because clotting is only delayed but not prevented
5.      It is not suitable for agglutination tests, coagulation studies  (prothrombin time tests or plasma  fibrinogen  determination )
6.      It may interfere with some automated biochemical analyses of  plasma (Schalms; 2006). 

In a study carried out  by Mahony  and  Fergusm;  1992 they found that heparin and other calcium -  chelating  anticoagulants have differing effects on platelets but no consensus was reached.
Platelets tends to Clump in samples collected into  low molecular weight   heparin (LMWH) precluding its use as  an  anticoagulant cited from (Am Jvet Res, 2001) . This was contrary to  what (Nwafia et al  2003) got  in  their study, they  concluded from their study that  there  is  minimal loss of platelet   in blood   stored in heparin  when compared to other  anticoagulants used in their  study   and  said heparin  have  sparing effect on  platelets (Nwafia et al,  2003).
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