Splanchnic substrate balance in malnourished patients during parenteral nutrition

Twenty-four-hour values for splanchnic substrate balance, O2 consumption, and CO2 production were estimated in nutritionally depleted patients, once while receiving 5% dextrose (D5W) and again after 6 or more days of glucose-based total parenteral nutrition (TPN). Nitrogen balance and whole body gas exchange were also measured. The majority of protein loss during D5W administration and the net protein synthesis during TPN occurred in the periphery. Increases in whole body and splanchnic O2 consumption occurred with TPN administration, but in both cases the splanchnic region accounted for 20% of whole body O2 consumption. Uptake of substrates by the splanchnic region was sufficient to meet splanchnic energy requirements. During TPN infusion uptake by the splanchnic region accounted for 60% of amino acids infused, whereas peripheral uptake accounted for 40%. Splanchnic uptake of glucose accounted for 20% of the glucose infused during TPN. During TPN the splanchnic region took up more glucose and amino acids than was required for energy needs and protein synthesis. It was assumed that the remainder of this substrate was used for lipogenesis. The splanchnic region accounted for 50 +/- 19% of whole body lipogenesis.