Jude, we just watched Top Copy Saturday night on IRC, and the same thing bugged me, too. However, the writer tried to cover it with a couple of things: when Clark was on the phone with his parents, he refused to go to the hospital because "the needles would break on [his] skin." So even though he was losing his powers, he retained his invulnerability, so dialysis wasn't an option.
Nan Smith did an excellent job of showing what the doctors could have done to help Superman, but I wonder how much good purges, etc. would have done 12 to 16 hours after ingesting the poison. Someone who knows more about it can probably point out how wrong I am, but I was under the impression that anything he swallowed would already be in the bloodstream by that point. It would have been more logical for his invulnerability to have failed so the doctors could have helped him with dialysis, if nothing else. But the emotional point of that scene was that Lois saved him when no one else could.
Personally, I think it would have been better to have the doctor mention that they'd tried all the purges, etc., but that the kryptonite was already in his bloodstream, so they weren't able to wash it out. If he had mentioned that they still couldn't pierce Sman's skin in order to cleanse his blood, the medical system wouldn't have sounded quite so ineffectual. On the other hand, there probably wasn't time for that within the 45 minutes of the show, so I'll imagine that that is what the doctor was telling L&S before the start of that particular scene.
