Plasma ionic calcium levels following injection of chloride, gluconate, and gluceptate salts of calcium.

The ionic equivalency of three calcium salts was tested in 15 patients undergoing cardiac surgery with extracorporeal circulation. Of the three salts tested (chloride, gluconate, gluceptate), only calcium chloride showed a reproducible and highly significant relationship between the increase in total calcium and the increase in ionic calcium. It is suggested that extracorporeal circulation may be one clinical situation in which use of a calcium electrode may be of major value. The marked distortion of plasma proteins and pH, the addition of large amounts of citrate, and the differences between various calcium salts indicate that it is probably not possible to predict ionic calcium with assurance and that direct measurement may be necessary for optimal therapy.