Ms. Wang is a 33-year-old female who just underwent a left mastectomy. As the attending is leaving the room she stops to ask if you know how to write “the normal postoperative orders for DVT prophylaxis.”
1. Why is DVT prophylaxis indicated in this patient?
2. What kind of DVT prophylaxis would you write for?
Deep venous thrombosis is frighteningly prevalent, especially in some pelvic and oncological surgical subgroups—approaching 50% of patients in some studies. While the data are less robust, an NIH consensus development panel has established the logical link between DVT and pulmonary embolism.
When deciding whether to write a patient for standing postoperative DVT prophylaxis, you should think about the patient’s risk profile. The most commonly encountered high-risk populations include those with cancer, patients who are not ambulatory, trauma patients, pregnant women, those with a history of a hypercoaguable disorder, and those who are older (increasing risk after age 40). The risk of DVT, however, must be balanced against the risk of bleeding, and the risk of side effects, as well as patient discomfort with multiple subcutaneous injections per day. Furthermore, patients who are at risk of a major bleeding complication (eg, neurosurgical patients) are usually not started on prophylaxis in the immediate postoperative period.
In summary, if the patient is low risk (and especially if the patient is expected to be ambulatory), then DVT prophylaxis is not necessary. If, on the other hand, the patient is at moderate or high risk for DVT, then the patient should always be written for DVT prophylaxis.
The Cochrane database has examined intermittent pneumatic leg compression and pharmacologic prophylaxis individually and together. Interestingly, pneumatic compression works by diminishing venous stasis, but also works because it promotes fibrinolysis (so you can even put the leg squeezers on the arms). The Cochrane review concludes that pneumatic compression plus pharmacologic prophylaxis (2500 U heparin 2 hours preoperatively and 12 hours postoperatively) is more effective than either strategy alone. Surprisingly, multiple studies report no increase in bleeding with this regimen.
While heparin is the oldest agent, it has a significant risk of causing heparin-induced thrombocytopenia (HIT) (2.6% in one meta-analysis). This contrasts with low-molecular-weight heparin (eg, enoxaparin or dalteparin) with a 10-fold decreased incidence of HIT in a population that consisted mostly of postoperative orthopedic patients. So, in general, it is better to use enoxaparin when you can—but you need to know, of course, when you cannot. There are only two common reasons that you might choose heparin. First, low-molecular-weight heparin is cleared renally, and so it can accumulate and lead to bleeding if given to a patient with renal insufficiency. Second, the half-life of low-molecular-weight heparin is longer than that of heparin and it cannot be easily reversed—both of which mean that heparin is preferred when the risk ...
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