FIGURE 131.22 Femoral artery and vein When using ultrasound dynamically, a one- or two-person approach can be used The two-person technique may be easier for the inexperienced ultrasound user In this scenario, one person is responsible for holding the probe and keeping the vein centered on the screen The proceduralist can then focus his or her attention on the patient, the site of puncture, and the ultrasound screen, without having to hold the probe In the one-person approach, the proceduralist holds the probe in the nondominant hand and inserts the needle with the dominant hand This requires more technical skill, but ultimately allows for improved awareness regarding needle tip location and more fine-tuned adjustments As the procedure begins, the vein is reidentified and centered in the screen In the dynamic technique, the transverse view is commonly used because it allows visualization of not only the intended vein, but also the nearby arteries and nerves in cross section (Fig 131.22 ) This short-axis approach is more successful for the novice user and should be the method of choice for beginners Alternatively, the vasculature can be identified in the longitudinal plane The long-axis approach is more difficult and requires greater skill; however, for the experienced sonographer, this view offers the advantage of visualizing the vein (and thus needle and catheter) along its entire course of cannulation ( Video 131.24 )