In their article on low-dose heparin thromboembolism prophylaxis, Owings and Blaisdell1 cited decreased levels of antithrombin III in severely injured patients as a reason for the failure of therapy with low-dose heparin. If this hypothesis holds true, then increasing the dose of unfractionated heparin, which would counteract the reduced bioavailability, or administering a product with predictable bioavailability such as low-molecular-weight heparin (LMWH) should be equally efficacious.
The authors mention that the primary problem with the use of LMWH is the inability to document the effect of a given dose except through measurement of ex vivo antifactor Xa activity. Clinical evidence is mounting that LMWH is an option for thromboembolism prophylaxis in high-risk patients without routine laboratory study monitoring.2 The antifactor IIa and Xa response differs with LMWH preparations. Therefore, these preparations should be evaluated individually for clinical efficacy.
The conclusions drawn in this literature review are not consistent
Hughes KM, Gonzalez LS. Low-Dose Heparin Thromboembolism Prophylaxis. Arch Surg. 1997;132(6):681. doi:10.1001/archsurg.1997.01430300123024