Have you soaked your feet in epsom salts?

Magnesium is the mineral that dilates blood vessels.

I had a patient with black hands from severe scleroderma. She had tried every drug out there to dilate her vessels with no results. She responded within a week to daily soaks with magnesium in tepid water. So I decided she needed oral, and added 800 IU of natural Vit E. And her fingers stopped being black, and the doctor stopped the warning about amputation etc.

There is another way to dilate blood vessels. I am using it now, myself, because my feet get really cold in the winter.
You can read about it here: Do not do this if you are taking drugs now for blood pressure, without supervision by your doctor. Do not use these supplements if you use nitroglycerine or other nitrates.
http://www.drignarro.com/

I think if both of these interventions fail, then you can decide about PN affecting the circulation.