When there is an access problem affecting clearance, does it always show up in the arterial and venous pressures first?

No .One reason could be recirculation.Have your clinic do a recirculation test to see if this is the problem.

Please define recirculation.

ACCESS RECIRCULATION is the measurement of the % of the whole blood that returns directly from the venous port to the arterial port without first passing through the heart and other vascular spaces of the body.Significant recirculation reduces the effectiveness of the Dialysis therapy. Hope this helps

Yes thanks. So then what causes recirculation, are there any telltale signs when recirc. is the problem, should anything else be ruled out (i.e high conductivity alarm keeps going off) before going to a procedure to check the access? What is that procedure called and what does it involve?

If the conductivity alarm keeps shutting the machine off on a day when your labs are being drawn, obviously it will affect your lab results-- and you should make sure your doctor is aware that it could be a machine problem before he/she sends you for a fistulagram.