Thrombin Generation after Abrupt Cessation versus Weaning over 8 hours of Continuous Infusion of Unfractionated Heparin in ICU-patients after Discontinuation of Continuous Venovenous Hemofiltration.

Background:

The F1K-MC-EVBR-trial (Xigris and Prophylactic hEparin in Severe Sepsis: XPRESS) study demonstrated that adult patients with severe sepsis receiving drotrecogin alfa (activated) with concomitant heparin treatment had an absolute 28 day mortality reduction of 3.6% compared to treatment with drotrecogin alfa (activated) combined with placebo. Evaluation of subgroups showed that patients receiving heparin at baseline who are assigned to treatment with placebo have a higher 28-day mortality (35.6%) and a higher incidence of venous thromboembolism (VTE) and other serious (thrombotic) adverse events than patients receiving heparin at baseline assigned to study treatment with heparin (26.9%). Patients who did not receive heparin previous to study enrollment performed similar to the latter group (placebo 28.9%, study-heparin 29.5%) [unpublished data]. A possible explanation for this difference in mortality and (thrombotic) adverse events could be that thrombin generation is increased as a result of discontinuing heparin treatment.




Our hypothesis is that rebound thrombin generation occurs in ICU-patients after abrupt cessation of heparin treatment in terms of elevation of coagulation-markers and reduction fibrinolysis-markers. IV weaning of heparin reduces this rebound thrombin generation.




Objective:

The objective op this study is to investigate whether thrombin generation is increased after abrupt cessation of intravenous unfractionated heparin (UFH) after discontinuation of CVVH. We further want to establish if there is a difference in thrombin generation after abrupt cessation of heparin versus intravenous weaning over a period of 8 hours.




Study design:

Prospective, randomized placebo-controlled, double blind study.




Study polulation:

Patients scheduled to stop treatment with CVVH because they no longer require it. (physicians discretion/local protocol).




Intervention:

One group of patients will start treatment with placebo simultaneous to stopping of CVVH at infusion rate similar to previous UFH infusion. Placebo will be stopped after 8 hours.

In the other group of patients UFH infusion will be reduced to 50% from the previous infusion rate. After 4 hours the infusion rate will be reduced again by 50% (25% of original infusion rate) and discontinued 4 hours later. Blood samples will be taken at specific intervals to evaluate thrombin generation.




Study parameters:

Markers of coagulation and fibrinolysis: aPTT, anti-Xa, factor VII/VIIa, TF, TFPI-antigen, TFPI activity, protein C / activated protein C, prothrombine fragment 1.2, TATc, ETP (Endogenous Thrombin Potential), Fibrin monomers, soluble thrombomodulin, PAPc, PAI.

Our hypothesis is that rebound thrombin generation occurs in ICU-patients after abrupt cessation of heparin treatment in terms of elevation of coagulation-markers and reduction fibrinolysis-markers; IV-weaning of heparin reduces this rebound thrombin generation.

N/A

Therapeutic protocol:

Prophylactic LMWH will not be given within 24 hours of discontinuation of CVVH. Patients are treated with help of standard guidelines effective in our units. The full medical treatment will be under the discretion of the supervising staff-intensivists who are not directly involved in the study.



Study protocol:

Randomization will take place using sealed envelopes:

1. In 10 patients UFH infusion will be stopped simultaneous to stopping of CVVH.

2. In 10 patients UFH infusion will be reduced to 50% from the previous infusion rate. After 4 hours the infusion rate will be reduced again by 50% (25% of original infusion rate) and discontinued 4 hours later.
Blood samples will be taken at specific intervals (see below) to evaluate thrombin generation.