Hawaii has a 6 month to a year waiting list at its dialysis centers. Plan early.
We actually emailed the dialysis centre in Kauai on October 8th for our trip starting January 12th. It was no problem at all. We had to change our dates about three weeks ago and again, it was no problem.
I should say that we're Canadians so maybe that has something to do with it. We're paying their "tourist rate" which might be more than they can charge Americans - don't know how that works.
Actually, it's harder for us here in Canada to travel within Canada. We switched our trip from the interior of B.C. to Palm Springs in April becuase there was no way he could get in for scheduled dialysis.