The first and, at times, most challenging step in transradial catheterization is vascular access. Although superficial, the radial artery is small, averaging 2.4 mm to 2.6 mm in diameter, compared with 7 mm for the femoral artery. Neurology textbooks suggest that the two-point discrimination limit of our fingertips is 2 mm-4 mm, making accurate palpation and cannulation of the radial artery difficult. The radial artery may also be collapsible, calcified, mobile, or associated with anatomic anomalies or dilated radial veins. The rate of crossover from transradial to transfemoral catheterization is 5% to 10%, with 57% of crossovers as a result of failure to access the radial artery.
Real-time 2D ultrasound guidance has been shown to facilitate safe and more efficient vascular access in central veins and in the femoral artery. We describe below how to apply this technology to transradial catheterization.