Abstract
Free fatty acid (FFA) and energy metabolism were studied in six severely burned humans after an 8-hr fast, after 1 hr of total parenteral nutrition, and after 72 hr of uninterrupted total parenteral nutrition. Caloric intake was twice the predicted basal metabolic rate, with 5 mg kg-1 min -1 of glucose, 2.5 g kg-1 day-1 of amino acid and the remainder of calories supplied as a fat emulsion. 1,2-13C-palmitate bound to albumin was continuously infused in order to quantitate FFA turnover and oxidation. Endogenous FFA turnover and oxidation were markedly suppressed by parenteral feeding, presumably due to increased insulin release. A modest recovery occurred in the initial suppression of FFA oxidation after 72 hr, but not in FFA turnover. Fat oxidation provided about one-quarter of the energy released during parenteral feeding, with endogenous FFA oxidation as the major component. This was roughly equivalent to the percentage of calories supplied as fat. This work indicates that the direct oxidation of a lipid emulsion contributes only a small amount of the energy released in the setting of the severely traumatized human receiving total parenteral nutrition but serves mainly to preserve endogenous fat stores. (Journal of Parenteral and Enteral Nutrition
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