The Effect of Heparin on Ionized Calcium Level and Blood Pressure

Heparin binds ionized calcium in vitro and possesses vasodilating properties when given as an intravenous bolus. In order to evaluate in vivo effects of heparin, 30 patients undergoing open heart surgery, were divided in two groups. 300 IU/kg bolus heparin was given intravenously to 20 patients in group I. Important decreases occurred in mean arterial pressure and ionized calcium levels in this group. 125 mg calcium chloride was given to 10 patients in group 2 just before bolus heparin administration. Ionized calcium levels become elevated in this group: there was no change in mean arterial pressure. These data suggest that slow injection of heparin would be beneficial in patients with low ionized calcium levels before cardiopulmonary bypass, especially in risky patients.