Argatroban is a parenteral direct Thrombininhibitor used for anticoagulation in patients suffering from heparin induced thrombocytopenia (HIT). There is increasing evidence suggesting that the activated partial thromboplastine time (aPTT), which is recommended for dosage monitoring, correlates poorly with serum argatroban concentration in critically ill patients. Therefore it may be badly suited to determine the correct dosing. Ecarin based tests have been proven to be effective in determining effects of direct thrombin inhibitors. The investigators now plan to evaluate a novel, rotational thrombelastometric, ecarin based bedside test for its ability to measure the effect of argatroban in critically ill patients. So far an excellent correlation of a similar test could be shown in spiked plasma of healthy adults. According to the manufacturer the ECA-Test is able to detect direct thrombininhibitors. However to our knowledge neither the ECA-Test nor other ecarin-based thrombelastometric tests have been studied in critically ill patients treated with argatroban. The investigators therefore seek to investigate the correlation of the ECA-Test (ClotPro®) with the serum argatroban concentration.

Inclusion Criteria:

• Continuous infusion of Argatroban in routine clinical use according to local standard of care
• Expected length of stay at ICU > 4 days
• 18 years

Exclusion Criteria:

• Heparin infusion in the last fourhours

All patients at the Intensive Care Unit who receive a continuous infusion of argatroban are eligible for inclusion.