Venous thromboembolism (VTE) remains a big problem for trauma professionals and the patients they take care of.  Every trauma center has some sort of VTE prophylaxis protocol for stratifying risk, prescribing mechanical or pharmacologic prophylaxis, and monitoring effectiveness.

This is all well and good for patients in the hospital. But what happens once they go home?  Who needs to continue chemoprophylaxis? For how long? And what product? These are all tough questions, and are not usually part of the protocol. It is an important issue, and I’d like to address the last question in this post.

Typically, patients who need ongoing chemical prophylaxis after trauma are sent home on a low molecular weight heparin product. This is usually enoxaparin. As you know, this drug has two possible dosing regimens for prophylaxis: 30 mg subq twice a day or 40 mg subq once a day.

Now, nobody likes to give themselves a shot, ever. But if one has the choice between once a day vs twice, I think it’s safe to say everyone would pick the single dose. But it just doesn’t seem right that 60 mg spread out over two doses is just as effective as 40 mg once a day. Unless, of course, we are radically overdosing on the twice a day regimen.

So is the one-a-day regimen as good as twice a day? There is older support in the orthopedic surgery literature that it is. However, general trauma patients are probably at higher risk than those old studies would suggest. The trauma group in Gainesville FL looked at this question. They had been using the once a day dose for years, then changed to twice daily administration. They performed a retrospective study of their experience.

Here are the factoids:

• The authors excluded the extremes of injury: patients admitted for < 2 days, or death within 2 days
• There were 409 patients in the once daily group and 278 patients with twice daily dosing
• About 3% of patients with once daily dosing developed VTE vs only 1% in the twice daily group
• Bleeding complications occurred in 1.8% of the once daily group vs 2.7% in the twice daily group
• Neither of these results was statistically significantly different

Bottom line: Although the authors try to imply that twice daily dosing “may be more effective” than once daily, they do admit that the statistics don’t show that. Unfortunately, the study design makes it nearly impossible to derive any firm results. It is a retrospective study designed long after the actual patient care, and does not take into account anything other than rudimentary risk stratification. 

My take on the topic is that it is unlikely that once daily dosing is as good as twice daily. Unfortunately, we just don’t have any literature to support that yet. Until we do, I recommend that you take a close look at your individual patient’s risk for VTE, and err on the side of giving enoxaparin twice daily until we know better.

Reference: Once- Versus Twice-Daily Enoxaparin for Venous Thromboembolism Prophylaxis in High-Risk Trauma Patients. J Intensive Care Med 26(2):111-115, 2011.