Disclosed herein are methods, systems and devices to monitor vascular volume status during renal replacement therapy utilizing at least one oximetry/photoplethysmography sensor. The methods, systems and devices provide an alternative to conventional vascular volume monitoring methods during renal replacement therapy while enabling reliable, non-invasive, and automatic monitoring of vascular volume to avert patient hypotension. The methods, systems and devices may be employed in the context of both inpatient and outpatient dialysis facilities and may also be incorporated into conventional hemodialysis and hemofiltration techniques and equipment.
