Insufficient Effect of Total Parenteral Nutrition to Improve Protein Balance in Peripheral Tissues of Surgical Patients

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Abstract
Previous studies have indicated that unstressed and malnourished patients do not necessarily obtain amino acid balance across peripheral tissues during total parenteral nutrition (TPN) treatment, indicating treatment inefficiency. Therefore, the aim of this study was to evaluate to what extent (prevalence) insufficient therapeutic amino acid balance occurs in surgical patients receiving TPN for standard medical reasons. Thirty-two patients treated in an ordinary surgical ward (n = 17) or in the intensive care unit (ICU) (n = 15) were examined. The arteriovenous balance across the leg of amino acids, glucose, glycerol, lactate, and oxygen was measured in relationship to plasma levels of insulin. All patients had been receiving TPN for at least 7 days before the investigation. All measurements were performed when amino acids had been infused for at least 4 hours and thus expected to support the resynthesis of lean body mass. Patients treated in the ICU and the surgical ward were in positive whole-body energy balance (+1127 ± 121 and +917 ± 123 kcal, respectively). Glucose uptake and oxygen consumption across the leg were similar in both patient groups. Glycerol release was not different from zero balance, indicating that inhibition of lipolysis across the leg during feeding and lactate was normally released in both groups. However, approximately 50% of the patients treated in the ordinary ward and 80% to 100% of the patients in the ICU remained in negative amino acid balance across the leg as judged from significant release of either methionine, tyrosine, or phenylalanine despite concomitant infusion of amino acids (~0.3 g of N per kilogram per day) and nonprotein calories. The results confirm previous results demonstrating that conventional TPN as used in many hospitals does not support efficiently the resynthesis of lean body mass in a considerable number of surgical patients. The reason for this is unknown, but it may be due to both the underlying disease and to less than optimal nutrition. (Journal of Parenteral Enteral Nutrition 15:669-675, 1991)