Deep venous thrombosis is a common concern in trauma care. Most trauma centers have well defined protocols for prophylaxis and surveillance. Ongoing use of pharmacologic thromboprophylaxis (PTP) in patients with traumatic brain injury (TBI), or in patients who need surgical procedures is controversial.  We have all experienced some form of “prophylaxis interruptus”, where our orthopedic or neurosurgical colleagues want us to forego or interrupt ongoing administration of heparin products. Does this create new problems?

A trial was conducted at two Denver trauma centers, trying to clarify the optimal administration of PTP in patients with stable TBI. One cohort received PTP, the other did not (either not indicated, short stay, or already on blood thinners). The group receiving PTP was also stratified into those who received it continuously and those who had interruptions in treatment.

They found that the incidence of DVT and PE was similar for patients receiving PTP vs those not receiving it. The two groups were very different, though, because the ones who did not receive it had less severe injuries and were more likely to be ambulating by discharge.  The most interesting finding was that being started on PTP and then interrupting it increased the incidence of DVT fourfold.

What is it about prophylaxis interruptus that is so risky? First, there were only 480 patients in this study, so statistical anomalies could be present. Could it be that the conditions (TBI) and operations that cause it to be interrupted greatly increase the risk? Unfortunately this study can’t answer those questions.

The bottom line: DVT and its prophylaxis is still a muddy concept. What we really need to do is to find out if PTP is really necessary in all the patients in whom we are using it. It would also be helpful if we knew how harmful it really is in patients with significant bleeding in their head, or in patients who need to undergo surgery. One alternative, if this paper pans out, is to begin with mechanical prophylaxis until cleared by neurosurgery and all operations are completed. For now, it’s not yet appropriate to change your existing practice and procedures.

Reference: Interrupted pharmocologic prophylaxis increases venous thromboembolism in traumatic brain injury. J Trauma 70(1):19-26, 2011.The term “prophylaxis interruptus” was coined by Tom Esposito in his discussion of this paper.