Does intravenous fat spare nitrogen in the injured rat?

The role of glucose versus fat as a source of energy in parenteral nutrition is controversial, particularly when administered after trauma, injury or in sepsis. In the present series of experiments, rats undergoing laparotomy and jugular vein cannulation were infused with hypertonic glucose or Intralipid with and without amino acids. The results demonstrate that the combination of amino acids and glucose has a better nitrogen-conserving ability than amino acids and fat, lasting at least 4 days after injury. However, when infused without amino acids, fat had the same nitrogen-conserving quality as glucose. The authors attribute the improved nitrogen-conserving quality of amino acids and glucose to the specific carbohydrate influence on amino acid metabolism, an action which is specific in both protein-free and protein-containing meals but has only very limited effect in the absence of simultaneously infused or fed amino acids. In the moderately to severely injured rat, a glucose calorie is significantly more effective in sparing nitrogen than a fat calorie.