Changes in serum calcium fractions and citrate concentrations during massive blood transfusions and cardiopulmonary bypass.

Total serum calcium, its fractions and serum citrate concentrations were measured in children receiving massive blood transfusion for scoliosis surgery, and in other children undergoing open heart surgery with cardiopulmonary bypass. During scoliosis surgery, although up to 100% of blood volume was replaced, and no additional calcium salts were infused, serum ionized calcium concentration remained within normal limits, provided that infusion rates of blood did not exceed 30 ml kg-1 h-1. During cardiopulmonary bypass, in which citrate-containing blood priming solutions were used, serum ionized calcium concentrations decreased markedly during perfusion associated with extremely high serum citrate concentrations. Serum ionized calcium concentrations returned to normal by the end of bypass, but serum citrate concentrations remained five times the normal concentration 5 h after bypass.