Uremic malnutrition is associated with increased risk of hospitalization and death in chronic hemodialysis (CHD) patients. Most nutritional intervention studies in CHD patients traditionally have used concentrations of serum albumin as the primary outcome measure and showed slight or no significant improvements. A recent study showed that intradialytic parenteral nutrition (IDPN) improves whole-body protein synthesis in CHD patients. On the basis of this observation, it was hypothesized that the anabolic effects of IDPN are associated with increases in the fractional synthetic rate of albumin, a direct estimate of acute changes in hepatic albumin synthesis. Seven CHD patients were studied during two hemodialysis (HD) sessions, with and without IDPN, using primed-constant infusion of (13C) leucine 2 h before, during, and 2 h after HD. Plasma enrichments of (13C) leucine and (13C) ketoisocaproate were examined to determine the fractional synthetic rate of albumin. The results indicate that administration of IDPN significantly improves the fractional synthetic rate of albumin during HD (16.2 +/- 1.5%/d versus 12.8 +/- 1.7%/d; P < 0.05) in CHD patients in parallel with significant improvements in whole-body protein synthesis (5.05 +/- 1.3 mg/kg fat-free mass/min versus 3.22 +/- 0.3 mg/kg fat-free mass/min; P < 0.05). IDPN is protein anabolic in the acute setting in CHD patients, as evidenced by significant concomitant increases in the fractional synthetic rate of albumin and whole-body protein synthesis.