Intensive care patients are at high risk to develop deep venous thrombosis and pulmonary embolism. Despite anticoagulation with heparin 7% of ICU patients suffer from this serious complication. Optimal regimens for prevention of VTE have been established in medical patients only and are not known for ICU patients.

It was therefore the aim of this study to compare the bioavailability of a low molecular weight heparin in ICU patients and in medical patients. Furthermore, we looked wether a 50% dose increase resulted in better bioavailability of this drug.

Background: The optimal dose regimen of low molecular weight heparins (LMWH) for thromboprophylaxis in critically ill patients is unknown.

Objectives: We performed a prospective, randomized study to determine anti-Xa activities following subcutaneous administration of 5000 IU or 7500 IU dalteparin for thromboprophylaxis in ICU patients compared with medical patients receiving the standard dose of 5000 IU.

Patients and Methods: Twenty-five ICU patients received 7500 IU (group 1) and 29 ICU patients received 5000 IU dalteparin subcutaneously (group 2) for thromboprophylaxis. Twenty-nine medical patients receiving 5000 IU dalteparin served as control group (group 3).

Inclusion Criteria:

• Requirement for prophylactic anticoagulation, patient age ³19 years, creatinine clearance within normal range, prothrombin time >30% and thrombocyte counts >100 G/l.

Exclusion Criteria:

• Estimated time of admission less than 24 hours, full anticoagulation, renal failure, history of heparin-induced thrombocytopenia, hereditary or acquired coagulation disorders.