Another recently identified factor associated with decreased serum albumin is hyperparathyroidism. A study by Tutal et al (Transplant Proc. 2006;38:2807-2812) of 127 hemodialysis patients looked at the effects of intact parathyroid hormone levels (iPTH) and CRP on laboratory values, including albumin and prealbumin, as well as rHuEPO requirements.
Patients with the highest iPTH (greater than 350 pg/mL) and CRP levels (greater than 8.5 mg/L) had the lowest albumin and prealbumin, as well as the highest rHuEPO requirement. Based on study results, the authors conclude that “hyperparathyroidism increases rHuEPO requirements and aggravates the negative effects of chronic inflammation in hemodialysis patients.”
In addition to inflammatory processes, metabolic acidosis has been associated with increased protein catabolism, oxidation of branched-chain amino acids, and decreased albumin synthesis in dialysis patients. Many studies have looked at the relationship of low serum bicarbonate and protein metabolism, including one by my colleagues and I (J Ren Nutr. 2003;13:205-211) examining the effects of increasing bicarbonate dose from 35 mmol/L to 39 mmol/L on nutrition-related outcomes in 248 maintenance hemodialysis patients.
Results of this six-month observational study showed serum bicarbonate was “inversely and significantly correlated with normalized protein catabolic rate (nPCR) at baseline and three months, and that nPCR decreased significantly from baseline at six months.” Although serum albumin did not change, we note that “study results support a mechanism for the loss of protein stores that is not closely linked to nutrition.”
The KDOQI clinical practice guidelines for nutrition in chronic renal failure (Am J Kidney Dis. 2000;35[6 Suppl 2]:S1-S140) note the importance of acid-base balance and recommend maintaining pre-dialysis serum bicarbonate levels at or above 22 mmol/L.
Adequate protein and calorie in-take remain essential components to improving outcomes for dialysis patients, and KDOQI nutrition guidelines recommend protein intake of 1.2 g/kg per day for clinically stable patients along with 30-35 kcal/kg per day.
KDOQI guidelines for CVD recognize that “the poor correlation documented between serum albumin and other nutritional parameters implies that non-nutritional factors may be more important in determining serum albumin levels than dietary intake and nutritional status per se in CKD patients.”