Dalteparin vs. unfractionated heparin for ICU DVT prophylaxis (PROTECT Trial)
Dalteparin is a low-molecular weight heparin that, unlike enoxaparin, is safe for people with renal failure. Among 3,746 ICU patients in 6 countries, followed until hospital discharge, there was no difference in the rate of proximal deep venous thrombosis (5.1% vs 5.8%, 1' endpoint) between once-daily dalteparin and twice-daily UFH, as detected by twice-weekly ultrasounds. There were less pulmonary emboli in the dalteparin group (2' endpoint; 1.3% vs. 2.3%, p=0.01; number needed to treat with dalteparin to prevent one PE = 100). Each LWMH may have unique properties and efficacies in different patient populations, and this trial does not answer the question of dalteparin's performance compared to other LMWHs, nor against q8hr UFH. (n=3,746). NEJM 2011;364:1305-1314.
Observations: Fully 80-90% of DVTs were clinically silent; i.e., detected only because of surveillance ultrasonography. Patients were much more prone to clots while in the ICU than on the medical floor. Of the 205 proximal DVTs, 182 occurred in the ICU, 23 on the ward; of 67 PEs, 47 occurred in the ICU. Only 13 of the 67 patients with a PE (19%) had a simultaneous proximal DVT. HIT was rare: less than 0.5% among all patients.
Check out Scott Aberegg's great blog post on the PROTECT trial on his Medical Evidence Blog, on how pulmonologists are patsies compared to cardiologists when going for "success" in clinical trial design.