These questions have been debated for years. Unfortunately, nephrologists often will not enforce any standard on their colleagues. However, no patient should ever be dialyzed without being examined first by a nephrologist or ordering physician with dialysis privileges. A nephrologsit can not bill for any acute treatment for which she/he is not present at least sometime during the treatment - night or day.
You should always recheck a K+ level before dialysis, if any K+ lowering drug was administered. Yes, the K+ will shift into and out of the cell, but the immediate level dictates the dialysate concentration for the treatment. K+ levels can be rechecked during the treatment.
The line/catheter should be in place and X-ray read, before the nurse is required to come to the hospital. But the nurse needs to be less than 30 or 60 minutes away from the hospital, if on call - whatever the time is for Emergent dialysis.