Total parenteral nutrition with the '3-litre bag': effect of fat emulsion on amino acid kinetics and nitrogen balance in patients with intestinal fistulae.

Three metabolically stable patients, receiving total parenteral nutrition as part of their management for post-surgical intestinal fistulae, were studied over a 16-d period in order to assess the effect of two different energy sources on protein metabolism. Nutrient intake was kept constant throughout except for the energy source: for half the time the patients received glucose alone, for the other half glucose plus fat emulsion (3:1 mixture). Amino acid metabolism, as indicated by rates of leucine turnover, was measured by constant infusion of [1-14C]-leucine for 24 h at the end of each of two 8-d periods. The rates of protein synthesis in the three patients (means of two measurements) were 5.15, 2.45 and 3.8 g/kg/d. No significant difference in nitrogen balance, plasma amino acid concentrations or amino acid kinetic rates could be detected whether energy was supplied as glucose alone or glucose plus fat. The extra expense of supplying energy as fat does not seem justified when total parenteral nutrition is given to stable patients for periods of up to 8 d.