Calcium Ion Activity During Rapid Exchange Transfusion with Citrated Blood

Measurement of ionized calcium levels by the technic of Soulier during massive transfusion of ACD blood supplemented with various quantities of calcium led to the apparently erroneous conclusion that ionized calcium levels would rise in the recipient when each unit was supplemented with 0.6 g CaCl2, the quantity which restores normal ionized calcium levels in vitro. Measurement of ionized calcium activity with the Orion electrode indicates that this ratio of CaCl2 will maintain an approximately normal ionized calcium level in dog recipients if it is infused simultaneously with the blood. Based on this information, it appears reasonable to assume that heparinized ACD blood, recalcified with 0.6 g CaCl2 per unit, may be used to prime the extracorporeal circuit for open heart surgery with the confidence that it will not alter the ionized calcium activity of the patient's blood. Addition of calcium to the circulation following administration of ACD blood causes a sharp rise and then a fall in the recipient's level of ionized calcium. Further studies in a variety of situations are required before final guidelines can be formulated for supplementation of ACD blood with calcium in massive transfusion.