What are the advantages of a F-70NR over a F-8 ?

Its better for phosphorous and B2M clearance.

Anyone know the composition of the two dialyzers?

Nick,

They are both made of the same material (polysulfone) but manufacturing process is different which gives them different clearance characteristics.

The F-70 NR can be considered a High Flux Dialyzer with A very larger surface area and a high UFR. I have expereinced trouble with this when a patients with low goal weights and long run times cause machine low TMP alarms. The end result is a continuosly howling machine that patient care staff interprets as machine related. Also there is a danger of Backfiltration. I eventually dumpe the F-70 For an F-80M. This had a much lower UFR but practically the same clearances as the F-70.
If its a question of a good Non reusable dialyzer stick to F-7's whitch have closer clearances to the F_8 as your main, all purpose dialyzer, and use the F-70 sparingly.

pbdtech,

Let me guess, you use Althin machines? We have the exact same problem with the TMP alarms. The basic software for the machines was written before high-flux dialyzers were widely used. We have addressed this issue with Baxter on numerous occations, requesting that they re-write the software so that high-flux dialyzers can be used without getting these alarms. Their responce is basically that they will think about it (which means don't hold your breath).