Traveling overseas is a little dicey on dialysis. Medicare information says it does not pay for dialysis outside the US and its territories. Most patients who do hemodialysis must go to a clinic to get dialysis whereas peritoneal patients carry or have their supplies shipped to their home or travel destination, which is treated as a temporary "home," Once you start on PD, I'd suggest you talk with your home training nurse, social worker or clinic billing staff about whether they can bill for PD while you're gone and if not, how much it would cost for the time you'll be gone. I'd also suggest you ask Baxter what you can expect to pay to get the supplies in Spain. According to this document on Baxter's website, they have home delivery of PD supplies in Spain so it may be less costly than shipping from the US, but then there's the question of how Baxter would bill your clinic for the suppies.
I'd plan to carry on some PD supplies and medications with you in case there's a travel delay so you can avoid missing treatments. Take a signed prescription for the supplies with you and you might want to contact the airline beforehand so you don't run in to problems at the airport. You may want to check out this article on Home Dialysis Central about traveling, which discusses traveling with the cycler or the transportable HD machine.
It is important to have contact information for a dialysis clinic in Spain where you could go if you have a problem with your catheter or get peritonitis? I would suggest that you check with Baxter or your home training nurse about how to find a clinic. Ask for copies of medical records to take with you, including your PD prescription, labs, x-rays, medication list, etc. Your clinic will know what to give you since it's what they send for patients who travel on hemodialysis.