Extend the skin insertion site Using the scalpel, make a small stab incision (< 5 mm) into the skin insertion site, avoiding contact with the guidewire, to enlarge the site and allow it to accommodate the larger diameter of the femoral arterial catheter. Place the catheter Advance the catheter over the guidewire to the skin surface: Hold the guidewire fixed at the skin surface, thread the catheter tip over the distal end of the guidewire, and slide the catheter down to the skin surface.