There was an article in a European newspaper several years ago that detailed the investigations into use of banned substances in the sport of cycling.
After a day of competition cycling a team would be chosen to be tested. The team doctor would always have several of the backup riders on the team set aside as non-drug users, so these guys would be sent to the testers first.
While they were testing those guys, the doctor and trainers had about 45 minutes to put IVs in the riders and flush the drugs out of their systems. Since they tested the guys in a serial fashion, they had time to do this.
The whole system is set up so that they can claim they are doing random testing but still give the teams time to take care of any evidence. It’s like most sports, there is a wink and a nod to testing for banned substances but there is little effort to actually stop it.
Highly unlikely given the fact that a typical kidney dialysis takes between 3 to 5 hours and a more thorough treatment takes 6 to 8 hours. And that's using highly sophisticated dialysis machines.
You can't "flush the drugs" out of someone's body via a 45 minute IV...In fact, a typical blood transfusion for one unit of blood takes over 1 1/2 hours.......and that's just to add blood, forget about cleansing all the blood in your body.