The SONOCLOT Analyzer (S1; Sienco, Inc. Boulder, CO USA, Model DP-2951) is used to perform kaolin-based activated clotting time as routine monitor of heparin therapy in patients undergoing cardiac operations. In addition, the device allows the assessment of the patient's coagulation status by a glass-bead activated test. Recently, a new SONOCLOT analyzer (S2) has been developed. As part of the routine management using S1, tests are also performed on S2. Results are entered into the cardiac surgery data base of all cardiac surgery patients and analyzed.

The SONOCLOT Analyzer (S1; Sienco, Inc. Boulder, CO USA, Model DP-2951) is used to routinely perform kaolin-based activated clotting time (kACT) as monitor of heparin therapy in patients undergoing cardiac operations on cardiopulmonary bypass.

Apart from kACT, the device allows the assessment of the patient's coagulation status by a glass-bead activated test (gbACT+, depicting also clot rate = CR and platelet function = PF). Recently, a new SONOCLOT analyzer (S2) has been developed. Although the S2 shares the technical fundamentals with the S1, the redesign of the device may result in performance changes of kACT and gbACT.

Routine management in cardiac surgery patients is guided using S1 and addition, tests are run on S2. Data are entered into the the cardiac surgery data base and S1 and S2 performance is compared by Bland-Altman analysis and % error calculation in order to establish new reference values.

Inclusion Criteria:

• all consecutive cardiac surgery patients

Exclusion Criteria:

• none

1 year