Question

Blood stored in citrate-phosphate-dextrose is better for hypoxic patients than acidic-citrate-dextrose because?

• A. It has less P₅₀
• B. It is less acidic
• C. The fall in 2, 3 DPG is less
• D. None of the above

Answer 1

The Correct Option is C

Frame it around oxygen delivery. A hypoxic patient needs transfused blood that actually releases oxygen to tissues, and that ability depends on 2,3-DPG keeping the dissociation curve shifted right (high P50). Stored blood loses 2,3-DPG over time, so the question is which anticoagulant protects it better. CPD, with its phosphate buffer and higher pH, blunts the fall in 2,3-DPG compared with the more acidic ACD, so option (c) is the answer.
Because ACD is acidic, glycolysis and 2,3-DPG synthesis are suppressed more, the curve shifts left, and the transfused blood clings to its oxygen instead of giving it up. CPD preserves 2,3-DPG, keeps P50 closer to normal, and supports better tissue oxygenation, which matters most after cardiac surgery or in any hypoxic state. Option (a) is the opposite of what you want, and although option (b) is factually true, the mechanistic reason the examiner wants is the smaller fall in 2,3-DPG.
Ref: Stored blood transfusion physiology.