MUSCLE PROTEIN-SYNTHESIS RATE DECREASES 24 HOURS AFTER ABDOMINAL-SURGERY IRRESPECTIVE OF TOTAL PARENTERAL-NUTRITION

Background: Muscle protein synthesis rate is known to decrease postope ratively as apart of the catabolic response to trauma Conventional tot al parenteral nutrition (TPN) in the postoperative period does not see m to counteract the decrease in protein synthesis. However, it is stil l unclear if ongoing TPN given continuously after surgery would inhibi t this fall in muscle protein synthesis. Methods: The rate of protein synthesis in skeletal muscle was determined before and 28 hours after open cholecystectomy, used as a standardized human model of trauma Pat ients (n = 14) were randomized to receive either TPN continuously thro ughout the postoperative period or saline as postoperative fluid thera py. The protein synthesis rate was calculated from the increase in enr ichment of labeled phenylalanine in protein after an IV flooding dose of [H-2(5)] phenylalanine, 45 mg/kg body weight. Results: The fraction al synthesis rate decreased by 31% from 1.74 +/- 0.13% to 1.15 +/- 0.1 0% per 24 hours in the saline group (p <.02) and by 23% from 1.59 +/- 0.10% to 1.22 +/- 0.07% per 24 hours in the group receiving TPN (p <.0 1), showing no significant difference between the two groups. Conclusi on: A continuous and ongoing infusion of conventional TPN started imme diately after surgery did not counteract the obligatory decline of mus cle protein synthesis, observed 24 hours postoperatively.