Effect of exchange transfusion (ET) on serum ionized calcium (Ca++)

Abstract

The citrate in ACD blood is known to complex Ca++ and calcium gluconate is usually infused during ET to counteract this effect. We have measured Ca++ with a Ca++ selective electrode during ET with non-buffered ACD and heparinized blood and have studied the effect of administering 0.1g calcium gluconate per 100 ml ACD blood exchanged. Heparinized blood produces negligible changes in Ca++, whereas with ACD blood a profound fall in Ca++ occurs even when calcium gluconate is given. Values for Ca++ during ET and ACD blood and added calcium gluconate are much lower in premature than in full term infants (p < 0.001). Omitting calcium gluconate further lowers Ca++ levels in full term infants (p < 0.05). The injection of calcium gluconate produces a transient rise in Ca++ which is rapidly neutralized by the infused citrate. Cessation of ET produces a prompt return toward normal values. No relationship was shown between Ca++, total Ca and protein. In spite of frankly hypocalcemic levels of Ca++ (particularly in prematures) no clinical evidence of tetany was seen. Ca++ levels could not be correlated with the infant's clinical state during the ET. We conclude that in full term infants the use of calcium gluconate in ET using ACD blood exerts a small but significant effect on Ca++. The clinical significance of this observation requires further evaluation.