Changes in red blood cell size and red cell fragmentation during hemodialysis

Introduction: Intradialytic hypotension remains the commonest complication for outpatient hemodialysis. The majority of relative blood volume (RBV) monitoring techniques monitor changes in hematocrit. As hematocrit can potentially be affected by changes in red cell size and hemolysis we studied the change in red blood cell size (MCV) during dialysis and hemolysis. Methods: MCV was prospectively measured in 176 stable regular adult hemodialysis outpatients (56% male, 27.8% diabetic, mean age 59.5 +/- 16.2 years) dialyzing against a range of dialysate sodiums (136-145 mmol/L), with cooled dialysate (35-36 degrees C), containing 1 g/L glucose, with constant ultrafiltration profiles. Red cell fragmentation was studied in 41 of the cohort. Results: Logistical regression analysis showed that the absolute change in MCV was related to the change in hematocrit (F=4.92, beta=0.111, p=0.031), and inversely with red cell shrinkage associated with predialysis osmolality (F=5.06, beta=0.83, p=0.029), and dialysate sodium (F=4.7, beta=0.34, p=0.035). There was no significant increase in red cell fragments during the dialysis sessions. Conclusions: Indirect assessment of RBV based upon the relative change in hematocrit, depends not only upon the change in plasma water and red blood cell numbers, but also upon MCV. Changes in MCV may theoretically lead to potential effects on RBV measurements.