Initially, crystalloid and colloid solutions may be used, but when replacement of blood lost reaches 40 per cent of the patient's blood volume, transfusion of red cells is required. Red cell concentrates may be used initially, but whole blood is preferable after the first 4 units of an anticipated massive transfusion, as some coagulation factors and proteins which may contribute towards normal hemostasis and colloid osmotic pressure are present in the plasma of whole blood.
Once the need for a massive transfusion is established, blood samples should be taken for compatibility testing (cross-matching) and also for baseline hemoglobin, platelet, coagulation, and biochemical measurements (T§.b!e,3). Normally, the patient's ABO and RhD group are determined, a red cell antibody screen is carried out, and the patient's blood is tested for compatibility with the donor's red cells. If blood is needed more urgently and the patient's ABO and RhD group are already known, ABO- and RhD-compatible blood can be issued without waiting for compatibility testing. If the patient's ABO and RhD group and antibody status are not known, then O RhD-negative blood may be given until the patient's group is determined. Switching to ABO- and RhD-compatible blood should be done as soon as possible for two reasons: first to avoid unnecessary use of O RhD-negative red cells, and second to minimize the volume of group O plasma in whole blood transfused to a group A, B, or AB patient as group O plasma contains anti-A and anti-B antibodies. Up to 10 units of group O whole blood can be given before the anti-A and anti-B antibodies present will cause significant problems with subsequent red cells of the patient's own ABO group.
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