From 1977.....
*** bq p. 53 Jehovah’s Witnesses and the Question of Blood ***
Will a transfusion immediately enhance the blood’s oxygen-carrying capacity?
Many persons believe that it will, but a recent editorial in Anaesthesia made this significant point: “It is worth remembering also that the haemoglobin of stored, citrated red cells is not fully available for the transfer of oxygen to the tissues for some 24 hours after transfusion . . . [...]
I worked in a blood bank during my younger years, and I am also a cell biologist, and i certify that this statement by the WT is absolute bullshit. You all can check that online. Hypothetically, the only limiting factor would be low temperature, but the blood is warmed before transfusion. The standard anticoagulant is citrate and it has no effect whatsoever on gas transfer.