The relationship between serum albumin and hydration status in hemodialysis patients

Abstract

Objective: A decreased serum albumin level predicts poor survival in end-stage renal failure. Hypoalbuminemia is multifactorial and related to poor nutrition, inflammation, and comorbid disease. Overhydration is also common in renal replacement therapy patients, and hemodilution may also contribute to a low serum albumin level.

Design: Crosssectional observational study.

Setting: Outpatient hemodialysis unit of a district general hospital.

Subjects: We investigated the relationship of serum albumin to C-reactive protein (CRP) and hydration state in 49 unselected hemodialysis patients (28 men).

Methods: Patients were assessed predialysis and postdialysis at their clinical dry weight. Extracellular fluid volume (Vecf) and total body water (Vtbw) were estimated by whole-body bioelectric impedance. Vecf was expressed as a percentage of Vtbw (Vecf%Vtbw). Predialysis CRP, predialysis and postdialysis serum albumin, and body weight were measured. Normalized protein catabolic rate (nPCR) and KT/V urea were calculated.

Results: Predialysis and postdialysis serum albumin levels were 36.9 g/L (95% CI, 35.7 and 38.1) and 41.4 g/L (95% CI, 39.7 and 43.3), respectively (P <.0001). Mean weight change was 2.0 +/- 1.2 kg. Predialysis and postdialysis serum albumin levels were negatively correlated with CRP (before: r = -0.393, P <.005; after: r = -0.445, P =.001) and positively with nPCR (before: r = 0.336, P =.018; after: r = 0.353, P =.013). Predialysis serum albumin level correlated with predialysis Vecf%Vtbw (r = -0.384, P =.006) and postdialysis serum albumin level with postdialysis Vecf%Vtbw (r = -0.654, P <.0001). In multivariate analysis, predialysis albumin was dependent on nPCR (P =.04), CRP (P <.0001), and predialysis Vecf%Vtbw (P =.002), and postdialysis albumin was dependent on nPCR (P =.01), CRP (P =.002), and postdialysis Vecf%Vtbw (both P <.0001). The increase in albumin was strongly correlated with both change in actual weight (r = -0.651, P <.0001) and change in Vecf%Vtbw (r = -0.684, P <.0001).

Conclusion: In unselected hemodialysis patients, serum albumin level is dependent on nPCR, CRP, and extracellular fluid volume. This relationship persists after dialysis, suggesting that many patients remain fluid overloaded at their postdialysis dry weight.