This can to be the reason itself for a surgical procedure in an emergency setting due to gastroenteral bleeding, rectus abdominis hematoma, psoas muscle hematoma, or can complicate the recovery of a surgical procedure. The question is, shall we prefer: thrombosis prophylaxis or hemorrhagic prevention?
This is a very important question.
There is a major push to implement DVT prophylaxis in the US. This is motivated by the so-called SCIP Core Measure Set implemented by The Joint Commission, the primary accrediting organization for hospitals.
http://tinyurl.com/bglktx2
It has been my personal experience that I have an increase in bleeding-related complications with DVT prophylaxis according to these guidelines. These include difficulties with intraoperative hemostasis, wound hematomas, and, rarely, bleeding requiring re-operation.
I have asked my colleagues informally about this and the result is universally similar. It is interesting that the SCIP Core Measure Set does not include identifying and reporting anticoagulant-related complications. The argument is usually that bleeding complications are rarely fatal and easily treated while pulmonary embolism is more likely fatal. I suppose internists all agree that bleeding is easily treated. Just call the surgeon!
Still, we need to collect all relevant data when experiments like this are imposed on a very large population.
It appears to me that the SCIP Core Measure Set is weighted toward a one-size-fits-all standard of measures that are very easy to quantify. Perhaps that is one reason why early data does not show differences in outcome between patients that meet SCIP Core Measures and those that do not. (There are other factors influencing these data as well.)
You also referenced patients coming in with ongoing anti-platelet and anticoagulant therapy. I do not know of any simple answer. It is always a trade-off between the urgency of surgery, the risk of bleeding, and the indication for the anti-platelet or anticoagulant therapy.