Palmitic acid kinetics in fasting, traumatized patients.

The contribution of free fatty acid oxidation to the elevation in energy expenditure after trauma has not been well characterized. Six control subjects and six traumatized patients were fasted for 48 hours and given a primed continuous infusion of (1-14C)palmitate to measure plasma palmitate and total free fatty acid kinetics. Traumatized patients had greater urinary nitrogen losses (20.8 vs. 9.3 g N per day) and a significantly greater ratio of measured to predicted resting energy expenditure (+36% vs. -6%) compared with controls. Individual and total plasma free fatty acid concentrations were similar for the two groups. The turnover and oxidation of plasma palmitate and total free fatty acids were not changed by multiple trauma. These results demonstrated that plasma free fatty acids and palmitate do not contribute to increased energy expenditure following trauma.

Evaluation of free fatty acid kinetics during TPN feeding of healthy rats.

Free fatty acid (FFA) kinetics were evaluated in TPN-fed healthy rats using a single fatty acid tracer. Rats were divided into three groups according to the nonprotein energetic substrate infused: glucose (A), monoacetoacetin-glucose (B), and lipid emulsion-glucose (C). Fat kinetics were measured by continuous infusion of [1-14C]palmitate. Total FFA and individual FFA concentrations were measured and turnover and oxidation were determined for the total pool of FFA and for palmitate. Groups A and B were similar in all parameters. Group C had increased total and individual FFA concentrations. Group C appeared to have decreased total plasma FFA turnover and unchanged oxidation compared to groups A and B. Palmitate appeared to have a 400% increase in oxidation and a 50% increase in turnover for rats in Group C when compared to Groups A and B. It is concluded that a single tracer does not accurately reflect plasma FFA during TPN using lipid emulsion.