Serum albumin concentration in dialysis patients: why does it remain resistant to therapy?

Serum albumin, transferrin, and prealbumin levels decrease as glomerular filtration rate (GFR) declines, even prior to the start of dialysis. The levels of these serum proteins are also associated with creatinine levels and lean body mass. Lean body mass also decreases with advancing renal failure. While all of these measures are regarded as reflections of nutritional status, each are strongly associated with any of several indicators of inflammation: positive acute-phase proteins or the cytokines that regulate their synthesis rate, in both longitudinal and cross-sectional studies. Inflammation in turn is associated with comorbid conditions, cardiovascular disease, chronic infections, age, and vascular access type. Additionally, dialysis patients are subjected to oxidative stress and exposure of blood to foreign antigens in the dialysis process that also potentially contribute to inflammation. In otherwise healthy individuals reduced protein and calorie intake does not cause hypoalbuminemia since albumin fractional catabolic rate (FCR) and resting energy expenditure (REE) normally decrease in response. The simultaneous occurrence of decreased protein intake and inflammation prevent these homeostatic compensations to reduced nitrogen and energy intake from occurring, resulting in decreasing albumin, transferrin, and prealbumin levels and loss of muscle mass. Nutritional intake may also be challenged as a result of renal failure associated with anorexia, gastroparesis, and socioeconomic factors, which may all cause nutritional intake to be sufficiently marginal so that the combined effects of inflammation and decrease protein intake are expressed as decreased visceral and somatic protein stores.