Plasma Volume, Albumin, and Fluid Status in Peritoneal Dialysis Patients

Background and objectives: Peritoneal dialysis (PD) patients may be overhydrated especially when inflammation is present. We hypothesized that patients with a plasma albumin below the median value would have measurable overhydration without a proportional increase in plasma volume (PV). Design, setting, participants, & measurements: We investigated a cross-sectional sample of 46 prevalent PD patients powered to detect a proportional increase in PV associated with whole body overhydration and hypoalbuminemia. PV was determined from I-125-labeled albumin dilution, absolute total body water from D dilution (TBWD), and relative hydration from multifrequency bioimpedance analysis (BIA; Xitron 4200) expressed as the extracellular water (ECW):TBWBIA ratio. Results: Whereas patients with plasma albumin below the median (31.4 g/dl) were overhydrated as determined both by BIA alone (ECW:TBWBIA 0.49 versus 0.47, P < 0.036) and the difference between estimated TBWBIA and measured TBWD (3.55 versus 0.94 L, P = 0.012), corrected PV was not different (1463 versus 1482 ml/m(2), NS). Mean PV was not different from predicted, and its variance did not correlate with any other clinical measures. Multivariate analysis showed that the only independent predictor of whole body overhydration was reduced plasma albumin. Conclusions: Hypoalbuminemia is an important determinant of tissue overhydration in PD patients. This overhydration is not associated with an increased plasma volume. Attempts to normalize the ECW:TBW ratio in hypoalbuminemic, inflamed PD patients may lead to hypovolemia and loss of residual renal function. Clin J Am Soc Nephrol 5: 1463-1470, 2010. doi: 10.2215/CJN.09411209