Rationale: No published randomized trials have compared low molecular weight heparin (LMWH) to unfractionated heparin (UFH) for thromboprophylaxis in medical-surgical ICU patients.
Objectives: A) Our Feasibility Objectives were to assess: 1) timely enrollment and complete, blinded study drug administration, 2) LMWH bioaccumulation in renal insufficiency, 3) twice weekly leg ultrasounds, and 4) recruitment rates for a future trial. B) Our Clinical Objectives were to assess 1) the effectiveness of LMWH vs UFH by estimating DVT, and pulmonary embolism (PE) rates, and 2) the safety of LMWH vs UFH regarding bleeding, thrombocytopenia and HIT.
Methods: In this prospective randomized stratified concealed blinded multicenter trial, we included patients ≥18 with expected ICU stay ≥72h. We excluded trauma, orthopaedic, cardiac, or neurosurgery, severe hypertension, DVT, PE or hemorrhage within 3 mos, INR >2ULN, PTT >2ULN, platelets <100 x109/L, creatinine clearance <30ml/min, therapeutic anticoagulation, >2 doses of heparin, and palliative care patients. By centralized telephone randomization, we allocated patients to dalteparin 5,000 IU QD SC or UFH 5,000 IU BID SC. All clinicians caring for patients were blinded except the pharmacist. Bilateral leg compression ultrasounds were performed within 48h of ICU admission, twice weekly, on suspicion of DVT, and 7 days post ICU discharge.
Results: A) Feasibility Objectives: 1) Timely, complete study drug administration occurred for >99% of scheduled doses; every dose was blinded. 2) No LWMH bioaccumulation was observed as measured by anti-Xa levels when creatinine clearance decreased to <30 ml/min. 3) Ultrasounds were performed without exception. 4) Estimated recruitment for a future trial is 4–5 patients/month/center. B) Clinical Objectives: 1) Effectiveness: Among 128 patients, 11 (8.6 %) had DVT, 2 (1.6 %) had PE. 2) Safety: 6 (4.7 %) had clinically important bleeds, 23 (18 %) had minor bleeds, 4 (3.1%) developed a platelet count <50 x109/L, and 2 (0.8%) had HIT diagnosed by serotonin release assay.
Conclusions: DVT rates remain high in medical-surgical ICU patients despite universal heparin thromboprophylaxis. This pilot study suggests that a randomized clinical trial comparing LMWH vs UFH feasible. An adequately powered trial is needed to achieve the clinical objectives.