There are so many new fibers out there that are formulated for just such accidents. Have you visited a carpet store yet? They will be able to direct you to a carpet that would be best for your situation.

When we recarpeted three years ago, we bought a good padding that had Arm & Hammer pet stain protection on the bottom to keep the pet stains from hitting the subfloor and it also blocks any odors that might already be there. That made a difference at the time--- with our old caret, our old dog had a habit of doing everything anywhere, and Allen was picking up on the habit. The padding blocked all of the old smells, and Allen has never had an "accident" anywhere the new carpet was laid down.