Bomholt T, Larsson S, Rix M, et al. - Given the management of fluid overload and anemia continues to be a challenge in patients receiving hemodialysis, and hypervolemia can be assessed employing a carbon monoxide (CO) rebreathing method by which blood volume (BV), plasma volume (PV), and red blood cell volumes (RBCV) can be ascertained, researchers investigated whether recurrent hypervolemia would cause hemoglobin (Hb) levels to be in the anemic range without a concurrent decrease in RBCV among patients receiving hemodialysis. Participants were 19 patients with type 2 diabetes who were on chronic hemodialysis. In participants, a CO rebreathing test was performed to determine BV, PV, and RBCV. The tests were carried out 20 minutes prior to dialysis start, and a comparison was performed between the measured intravascular volumes vs predicted normal intravascular volumes according to Nadler's equation. The CO rebreathing test represents a novel way to determine intravascular volumes in hemodialysis patients. Expanded predialysis BV was noted, relative to predicted intravascular volumes, in the majority with high PV as the main reason. Between the measured and predicted volumes, there was no overall variation in RBCV. Based on predialysis Hb levels, all but one patient was identified as anemic, but only 9 were found to be in the anemic range according to the measured RBCV, suggesting Hb dilution.