Ultrasonographic investigation of the effect of reverse Trendelenburg on the cross-sectional area of the femoral vein.

Emergency physicians often obtain central venous access via the femoral vein in critically ill patients or patients with difficult peripheral access due to chronic intravenous drug use. Previous studies using two-dimensional ultrasonography have demonstrated that the Trendelenburg position increases the cross-sectional area of the internal jugular vein. This study is designed to determine the effect of the Reverse Trendelenburg position on femoral vein dimensions using bedside ED ultrasonography. A prospective, non-randomized observational study was conducted that enrolled subjects at an urban Level I Trauma Center and an affiliated School of Medicine over a 2-month period. Informed consent was obtained from 52 adult subjects with no history of deep venous thrombosis or vascular surgery in the lower limbs. Using two-dimensional ultrasound with a 7.5-MHz linear transducer, femoral vein cross-sectional areas on the right and left sides were measured with subjects supine, and in approximately 15 degrees reverse Trendelenburg. The data was analyzed using a two-tailed Student's t test. The mean cross-sectional area of the femoral vein with subjects supine was 0.85 cm(2) (SD +/- 0.41 cm(2)), and 1.22 cm(2) (SD +/- 0.51 cm(2)) with subjects in reverse Trendelenberg. The cross-sectional area of the femoral vein increased significantly (p < 0.001) with the reverse Trendelenburg position [55.2% +/- 9.1% (95% CI)]. In conclusion, a significant increase in femoral vein cross-sectional area can be achieved with the reverse Trendelenburg position. This maneuver may increase the rate of successful femoral vein catheterization.