Total and ionized calcium levels during open heart surgery with two different pump priming solutions

Changes of total (Ca) and ionized Ca-levels (Ca2+) were studied during open heart surgery in 18 patients. 9 patients (group A) had only crystalloid solutions as pump priming, the other 9 patients (group B) had 500 ml of citrated whole blood in the priming solution. For assessment of hemodilution hct and total plasma protein and plasma albumin were determined. Measurements were done preoperatively, before and after systemic heparinisation, during and after extracorporeal circulation (ECC) and on the first postoperative day.

1. Anticoagulation with 375 U/kg BW heparin had no effect on ionized calcium levels. 2. With onset of ECC (Ca) decreased by 30% in group A and by 20% in group B. (Ca2+), however, decreased by 20% in group A and by 35% in group B. The percentage of ionized calcium increased by 15% in group A whereas it decreased by the same amount in group B. This difference is contributed to the calcium binding effect of citrate added to pump priming in group B. Mechanisms of the relative increase of ionized calcium during ECC in group A, however, remain to be studied.