Getting cat pee out of mattress is beating me

Act fast if it's fresh - blot (don't rub) as much as you can with towels. Then spray with a mix of white vinegar and water, roughly half and half, and blot again. Once it's mostly dry, cover the spot with baking soda. Then mix hydrogen peroxide (the 3% stuff) with a few drops of dish soap and spray that over the soda till it fizzes. Leave it to dry fully, a good 8 hours or more, then hoover the powder up. Test the peroxide on a corner first, it can lighten some fabrics. If it still smells after that, an enzyme cleaner from a pet shop is what actually breaks the urine down. A mattress protector afterwards saves doing this again.