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Heparinization of samples for plasma ionized calcium measurement
1Department of Anesthesiology, University of Utah Medical Center, Salt Lake City.
Maintenance of normal plasma ionized calcium concentration forms part of the management of the critically ill patient; it is, therefore, important to measure accurately plasma ionized calcium. We have compared the ionized calcium concentration of blood samples heparinized with a carefully measured amount of heparin with that of blood samples heparinized in the conventional fashion. The amount of heparin in the deadspace of a syringe was demonstrated to artifactually lower the plasma ionized calcium concentration. Samples for plasma ionized calcium measurement should be heparinized with a measured quantity of heparin, since the conventional technique introduces an unknown and probably excessive quantity of heparin into the syringe deadspace.
Maintenance of normal plasma ionized calcium concentration forms part of the management of the critically ill patient; it is, therefore, important to measure accurately plasma ionized calcium. We have compared the ionized calcium concentration of blood samples heparinized with a carefully measured amount of heparin with that of blood samples heparinized in the conventional fashion. The amount of heparin in the deadspace of a syringe was demonstrated to artifactually lower the plasma ionized calcium concentration. Samples for plasma ionized calcium measurement should be heparinized with a measured quantity of heparin, since the conventional technique introduces an unknown and probably excessive quantity of heparin into the syringe deadspace.