Whole Body Protein Turnover, Synthesis, and Breakdown in Patients Receiving Total Parenteral Nutrition before and after Recovery from Surgical Stress

This study was conducted to understand further the mechanisms underlying the loss of body nitrogen after trauma. Six patients who underwent abdominal surgery and six for control were studied. The measurement of whole body protein turnover was made on the 3rd and 10th postoperative day during total parenteral nutrition with constant infusion of [ 15 N]glycine according to Picou and Taylor‐Roberts. The measurement was also made on six control patients during total parenteral nutrition in the nonstressed state. The rates of whole body protein turnover, synthesis, and breakdown were calculated from the plateau 15 N enrichment of urinary total N, which was analyzed with a mass spectrometer. The values were compared with control by Student's t‐test, and the changes in the individual patients were examined by a paired t‐test. Immediately after the operation, whole body protein turnover and breakdown were significantly elevated (p < 0.05 and <0.02, respectively), and decreased with the improvement of N balance after recovery from stress by 0.95 ± 0.21 and 0.61 ± 0.13 g. protein/kg.day, respectively. The changes in whole body protein turnover and breakdown were statistically significant (p < 0.005 and <0.005, respectively). However, no tendency of alteration in whole body protein synthesis was found throughout the study. It is concluded that protein turnover rate increases in surgical stress, and that the increased protein catabolism rather than the alteration in synthesis could account for the postoperative nitrogen losses. (Journal of Parenteral and Enteral Nutrition 9 :452–455, 1985)