Deep Vein Thrombosis (scanning tutor)

Introduction

Although not one of the original six American College of Emergency Physicians indicated exams, evaluation for deep vein thrombosis (DVT) is one of the most useful exams for critical care physicians. There are approximately 250,000 new diagnoses of DVT per year and 50,000 deaths from thromboembolic disease annually (1,2). The estimated rate of propagation from DVT to pulmonary embolism ranges from 10% to 50% (1,2). Because the incidence of DVT is so high and because this disease is so prevalent in critical and acute care settings, the ability to rule in or rule out DVT at the bedside is a particularly powerful tool. The simplified compression technique described in this chapter evaluates for DVT at two anatomic sites of the lower extremity venous system. This protocol has been evaluated in multiple randomized controlled studies and has become a well-accepted protocol used for decision making in conjunction with clinical pre-test probability assessments (3–12)

Focused Questions for DVT Ultrasound
The questions for DVT ultrasound are as follows:

1. Does the common femoral vein fully compress?
2. Does the popliteal vein fully compress?

Anatomy
The anatomy of the lower extremity should be reviewed so the DVT compression ultrasound exam can be done properly. The ileac vein becomes the common femoral vein (CFV) as it leaves the pelvis. The most proximal tributary of the CFV is the greater saphenous vein (GSV) (Figure A). The common femoral then splits into the superficial and deep femoral in the proximal thigh – both of these vessels are part of the deep venous system despite their names. At the knee, the superficial femoral becomes the popliteal vein running in the posterior fossa of the knee joint and is joined by its tributaries, the tibial vein and peroneal vein . It is not surprising that clots, as shown by venography studies, seem to cluster at the branch points of the venous system. One common explanation is that the increased turbulent flow at these branch points produces increased wear and tear on the vessel walls, thus making these areas predisposed to clot formation. Data from these venography studies support the use of the simplified compression
technique because identification of clot in the popliteal vein or CFVshould identify any DVTs dentified by venography ; there were no cases in these initial studies where a DVT did not involve the popliteal vein, CFV, or both.



Proximal venous system. Courtesy of Dr. Manual Colon, Hospital of the University of Puerto
Rico, Carolina, Puerto Rico.