Short-term effects of an intravenous infusion of a nutrient solution containing amino acids, glucose and insulin on leucine turnover and amino acid metabolism in patients with liver failure

Tolerance to an intravenous nutrient infusion containing amino acids, glucose and insulin was assessed in 12 adult patients with clinical and biochemical evidence of liver failure. In six individuals, fasting plasma amino acid patterns and turnover rates were measured by a constant intravenous infusion of [1-14C]leucine tracer. In the remaining patients the same measurements were made after a 10 h intravenous infusion of a 'standard' commercial mixture of amino acids (3.4 g/h), dextrose (20 g/h) and insulin (1.6 units/h). On the second day, conditions were crossed over and measurements were repeated. With the exception of glycine, the infusion of the amino acid-containing solution failed to significantly increase plasma amino acid content. Plasma leucine flux measurements indicated that the explanation involved a reduction in input of amino acids derived from the breakdown of body proteins rather than an increased uptake of amino acids into protein; i.e., the rate of liberation of leucine from protein decreased by an average of 2.4 mmol/h (P less than 0.05) whilst intake only added 1.6 mmol/h. No consistent changes in encephalopathy were observed. In conclusion, the infusion of the amino acid solution together with glucose and insulin resulted in improved nutritional intake and had no deleterious short-term effects on encephalopathy. However, judging from the plasma amino acid concentrations, the composition of the commercial mixture could be improved by reducing the glycine content.