Calcium chloride and calcium gluceptate were compared in their ability to increase plasma ionized calcium concentrations ([Ca2+]). To correct a low ionized calcium concentration, each of 10 critically ml of a 10% solution, containing elemental calcium 27 mg ml-1) and calcium gluceptate (20 ml, containing elemental calcium 18 mg ml-1) over a 5-min period in randomized order approximately 6 h apart. [Ca2+] and haemodynamic variables (mean arterial pressure (MAP), mean right atrial pressure (RAP) and heart rate (HR)) were monitored for a 30-min period following completion of calcium infusion. Infusion of either calcium preparation was associated with similar increases in [Ca2+] (5 min after infusion of calcium chloride: 33 +/- 3.1%; calcium gluceptate: 32 +/- 4.3% (mean +/- SEM)) and the effects on MAP were similar for each solution (11.1 +/- 1.8% and 9.7 +/- 2.4%, respectively).