Yes, I agree. I work in Acute Hemo, and we neither access patients below 80 systolic nor return them below that... very rare to return one below 90. However, there are a handful of patients who are absolutely asymptomatic with systolics in the 70s... that's just where their 'normal' is (strange as it seems, and they make me nervous as hell). We take VS Q15min throughout treatments, and pay attention when the pressures start creeping down, but do not generally treat it unless a) it is in the 80s and/or b)they are symptomatic (lightheaded, cramping, decreased responsiveness, change in mental status, etc.) We are taught "treat the patient, not the number."
I also agree that our Nephrologists would not have bolused the patient with 2L NS... shoot, that's probably all the fluid they got off during the treatment, and now it's been put right back on -- far too quickly! --, threatening them with fluid overload and wet lungs, plus whatever other fluids they take in over the next 2 days until their next treatment. Which means the next treatment we have to try for MORE fluid, which will cause a more unstable blood pressure.
My suggestion would have been Albumin 25-50g given slowly, or Mannitol, which would encourage fluids to shift from the tissues into the vascular system. Had the patient been symptomatic, I would suggest reviewing the "dry weight" (ultrafiltration goal) because it may need to be changed due to change in actual body composition.
What we generally see in Dialysis is patients coming in with high blood pressures, which are gradually lowered throughout the treatment as we pull off fluid. After a period of time (hours after the treatment, when the person's fluids have shifted from the tissues to the vascular system quite normally on their own), you'll see the blood pressure rise again. Simple osmosis, nothing more, which is why the Albumin or Mannitol often work.
Sounds like there was an unfortunate breakdown in communication here...