Will the needle or i.V. Hurt during the upper extremity CT scan with dye?

It shouldn't. Once the IV is in, injecting fluid into your veins shouldn't hurt, as there are no pain receptions inside your vessels. In some cases the IV can "blow out" or infiltrate and the fluid will go around the vessel and not into the vein. This can hurt and cause other complications. Elderly patients with fragile veins are the most at risk for IV infiltration.