Surgery Fluid, Electrolyte and Nutrition fa24f3d0 Massive blood transfusion is defined as: A Whole blood volume in 24 hours B Half blood volume in 24 hours C 40% blood volume in 24 hours D 60% blood volume in 24 hours High-Yield Explanation Massive transfusion is defined, in adults, as replacement of whole blood volume in 24 hours or >50% of blood volume in 4 hours.