Unless a friend or relative is trained and willing to fill in, then I don't think there is any other option than to go in-center. I know I wouldn't want my husband to have to go in-center if I had to be away but I also know that he'd be in good hands at the center he is assigned to as a backup, opposed to him getting dialysis at a hospital where they are complete strangers and we do not know their level of experience, skill or care. Hate to say it but I think any center may be better than dialysis in a hospital. (we've been there, done that...was awful).
NxStage is experimenting with in-center facilities where I hope a patient could go on occasion to spell their caregiver.