The macroanionic activity of heparins in the presence of dextrose and calcium ion

The effect of dextrose on heparin was investigated using the heparin-azur A interaction as a measure of macroanionic activity. Dextrose solutions did not diminish heparin-azur A metachromasia but prior autoclaving of the dextrose solution resulted in a slight decrease. When calcium chloride was added to the dextrose (autoclaved or unautoclaved) there was a reduction which was greater than that caused by calcium ion in the absence of dextrose. The effects of calcium ion and dextrose acting together were each concentration - dependent. A low molecular weight fraction (8400) was more susceptible to the effects of calcium in the presence of dextrose than a fraction of mol. wt. 19 000, hence unfractionated heparins with different amounts of various fractions may respond differently to calcium in the presence of dextrose. This has not been considered in earlier studies of the anticoagulant activity of unfractionated heparins in dextrose infusion and could has contributed to reported discrepancies, particularly in view of the variety of test methods used. At present, it is not possible to predict from in vitro tests whether dextrose will modify the in vivo anticoagulant activity of heparin.