Bedside ultrasonography detects significant femoral vessel overlap: implications for central venous cannulation

Objective: Our goal was to gain a better understanding of the femoral vessel anatomy as it relates to central venous cannulation. The primary objective of this study was to use bedside ultrasonography to determine the amount of exposed femoral vein at three sites corresponding to surface anatomy of the landmark-based procedure. Methods: This cross-sectional study enrolled a random sample of 180 adult patients presenting to a large urban academic emergency department. Subjects underwent standardized ultrasonography to identify and measure the depth and diameter of the femoral vessels and amount of exposed femoral vein at the level of the inguinal ligament (0 cm) 2 cm and 4 cm below. Repeated measures analysis of variance was used to determine significant relationships between vessel measurements and distance from the inguinal ligament. Results: The median age was 44.5 (range 19-90) years; 101 patients were male. The mean (+/- SD) percentage of exposed vein at the inguinal ligament was 83% (+/- 21). This decreased significantly (p < 0.01) with increasing distance from the inguinal ligament: 65% (+/- 25) at 2 cm and 56% (+/- 30) at 4 cm. At every distance away from the inguinal ligament, there were some subjects with no vein exposed. Conclusion: This study demonstrates significant overlap of the femoral vessels at sites where landmark-based femoral vein cannulation is often attempted. Our results suggest that ultrasound guidance would be beneficial as femoral vein cannulation may be difficult or impossible in certain individuals owing to anatomic variations.