154 mEq/L sodium bicarbonate solution, administered intravenously at 3 mL/kg/hr for 1 hour before cardiac angiography, followed by an infusion of 1 mL/kg/hr during and out to 6 hours after cardiac angiography, or 154 mEq/L sodium chloride solution (0.9% normal saline), administered intravenously at 1 mL/kg/hr for 8 12 hours before cardiac angiography, followed by an infusion of 1 mL/kg/hr during and out to 8-12 hours after cardiac angiography