Impact of Sonoclot hemostasis analysis after cardiopulmonary bypass on postoperative hemorrhage in cardiac surgery

Purpose: The Sonoclot Analyzer provides a functional test of whole blood coagulation by measuring the viscous property of the blood sample. In this study, we used a modified Sonoclot assay, using cuvettes with a glass bead activator containing heparinase, and compared the Sonoclot data before and after cardiopulmonary bypass (CPB) to assess the usefulness in predicting postoperative hemorrhage. Methods: In 41 cardiac surgery patients, Sonoclot data were obtained immediately after heparin administration (pre-bypass) and just before protamine administration (post-bypass). Excessive bleeding was defined as chest tube drainage greater than 2 ml·kg^-1 ·h^-1 in 1 h during the first 4 h after surgery. Results: There were no significant differences in Sonoclot values before and after CPB in patients with acceptable bleeding (n = 29). In patients with excessive bleeding (n = 12), Sonoclot variables reflecting fibrin formation (activated clotting time [ACT], rate of fibrin formation [clot rate], and peak clot signal) were preserved after CPB; however, the variables reflecting platelet-fibrin interaction (time to peak, peak angle, and clot retraction rate) were significantly different from their respective pre-bypass values. Sonoclot analysis showed impairment of clot maturation after CPB in patients with excessive postoperative bleeding. Conclusion: Our results suggest that abnormal postoperative hemorrhage can be predicted by Sonoclot analysis with a new glass bead-activated heparinase test performed after CPB.