Question

When blood is taken out, anticoagulants like oxalate/sodium citrate can be added to prevent blood clotting. These anticoagulants work by

• A. Preventing action of blood clotting factor III
• B. Preventing action of heparin
• C. Preventing action of blood clotting factor IV
• D. Promoting the action of heparin

Answer 1

Answer: (C)

Preventing action of blood clotting factor IV

A) Anticoagulants like sodium citrate depress prothrombin (prothrombin is blood clotting factor II) activity by precipitating ionized calcium (calcium aids in clotting). Blood clotting factor III is tissue thromboplastin (tissue factor) which is not affected here.

B) Heparin is an anticoagulant by itself.
C) Ionised calcium ${Ca}^{++}$ is blood clotting factor IV. Its action is prevented by anticoagulants like oxalate/sodium citrate.

D) These anticoagulants do not promote the action of heparin.

So the correct answer is 'Preventing action of blood clotting factor IV'.