Abstract
STUDY OBJECTIVES 1) To develop an in vitro system to simulate the kinetics of ionized calcium in mixed venous blood during rapid transfusion of fresh frozen plasma (FFP) and 2) to use the in vitro data to estimate the effect of the transfusion rate relative to cardiac output (CO) on ionized calcium. DESIGN Experimental study. SETTING Research laboratory of an academic hospital. MEASUREMENTS Citrated FFP was mixed with compatible heparinized whole blood at various volume ratios in vitro to simulate the mixed venous blood obtained at various flow ratios of FFP transfusion to the recipient's venous system in vivo. Ionized calcium was measured after each mixture. MAIN RESULTS Mixing FFP and whole blood at volume ratios of 0:100, 5:95, 10:90, and 15:85 yielded ionized calcium levels (mean ± SD, mmol/L) of 1.23, 0.81 ± 0.02, 0.54 ± 0.08, and 0.34 ± 0.02, respectively. The 50% reduction in ionized calcium occurred at a volume ratio of 7:93. CONCLUSIONS An instantaneous 50% reduction in ionized calcium occurs in vitro at a proportion equivalent to a transfusion rate of FFP representing 7% of CO.
