Ionized calcium monitoring during liver transplantation.

Ionized calcium concentration was measured in five patients undergoing liver transplantation. Varying degrees of decreased ionized calcium were observed in all cases and can be attributed to the chelation of calcium by the citrate added during blood transfusions, the inability of the patient to metabolize citrate by the liver during the anahepatic phase of the transplant, and hemodilution of the blood volume with the perfusion prime during venovenous bypass. Calcium chloride was administered when necessary as guided by ionized calcium measurements to restore concentrations to levels that maintain adequate cardiac output. Because of the serious hemodynamic consequences of severe hypocalcemia, regular monitoring of ionized calcium concentration is necessary during this procedure. Total calcium levels are not reliable for this because they do not reflect the extent of anion binding.