Anatomical Landmark vs. Ultrasound Identification of the Femoral Vein

Fast, accurate femoral vein identification is important for providing life-saving therapies via central venous access in the emergency department.

We aim to determine the accuracy of the anatomical landmark technique for finding the femoral vein vs. the ultrasound-guided technique. We hypothesize that the femoral vein location using anatomical landmarks is, on average, 10 mm or more away from the femoral vein location found using ultrasound.

A convenience sample was recruited from a large county emergency department and the femoral vein location was determined through both methods, with the location determined by ultrasound being considered the true location of the vein. The mean distance between the ultrasound-guided femoral vein location and the anatomical landmark estimates (defined as "delta") was measured. Data were transformed on a natural log scale and p-value for mean delta > hypothesized mean was reported. For exploratory subgroup analysis, p-value for a nonzero difference between subgroup delta means was reported.

A total of 87 patients consented to participate. The average delta was 14.29 mm, which was significantly higher than the hypothesized mean (p = 0.0038). Subgroup analysis suggested that the average delta in the body mass index (BMI) < 25 group was significantly lower than the average delta in the BMI ≥ 25 group (11.77 mm vs. 16.23 mm; p = 0.0157). Measurements made by researchers with hand length of < 205 mm were significantly different from those made by researchers with hand length of ≥ 205 mm (17.42 mm vs. 11.74 mm; p = 0.0020). However, the average delta between the anatomical landmark estimate and ultrasound-guided location in the BMI < 25 group and researcher hand length ≥ 205 mm group still exceeded 10 mm.

Therefore, the anatomical landmark technique is not accurate in identification of the femoral vein within 10 mm of the true location determined by ultrasound.