Ionized calcium in exchange transfusion with THAM-buffered ACD blood

In 20 exchange transfusions with THAM-buffered ACD blood 5 ml. of 2% calcium gluconate (8 mg. elemental calcium) was injected after each 100 ml. of blood exchanged. Plasma ionized calcium decreased significantly during the procedure, although after each injection of calcium gluconate, levels returned briefly to normal. Ten minutes after the end of exchange ionized calcium had returned to pre-exchange levels and remained there until at least 30 mins. postexchange.

Total calcium also increased significantly. Short periods of extreme hypercalcemia (between 7 and 8 mEq./l.) were noted after each injection of calcium gluconate.

The amount of calcium gluconate was insufficient to counteract the calcium-chelating effect of citrate. If no heparinized blood is available we suggest adding heparin and calcium chloride to THAM-buffered ACD blood to avoid the repeated sudden fluctuations between low and high calcium ion activity.