Experimental hypercalcaemia and whole blood clotting

SYNOPSIS Experimental hypercalcaemia was induced in rats by (1) transplantation of the solid Walker 256 tumour, and (2) intraperitoneal injections of calcium gluconate. Whole blood clotting was studied by means of thromboelastography and whole blood clotting times in polystyrene and glass test tubes. At serum calcium levels between 10-3 and 115 m-equiv/l a slight delay in clot formation was found which was reversible by the addition ofEDTA to whole blood. Acute, calcium-gluconate-induced hypercalcaemia, however, leads to a significant shortening of the clotting time in the polystyrene tube and to a lesser degree in the glass tube. Maximal factor XII activation in vitro with ellagic acid levels the difference of clotting times again. From these experiments it is con-cluded that acute hypercalcaemia induces a hypercoagulable state, possibly by partial contact activation, and thus may favour thrombus formation in vivo. It is well established that the presence of calcium ions is essential during the course of the enzymatic cascade of blood coagulation. In vitro the calcium concentration may be reduced by at least one half before any defect in blood clotting is observe