The Effect of Intravenous Nutrition in Patients Undergoing Abdominal Surgery

1. Goals The overall goal of perioperative nutrition support is to abolish protein wasting and to promote anabolic processes by directing amino acids into protein synthesis rather than oxidation. Protein repletion and enhancement of anabolism appear to be particularly important in cancer patients who enter major abdominal surgery in a catabolic state.

2. Objectives The objectives of this research program are

   • to examine whether the anabolic effects of hypocaloric nutrition depend on the degree of catabolism before the operation and thus identify patients who benefit the most from perioperative nutrition support (study I)
   • to investigate whether excluding glucose from hypocaloric nutrition, i.e. infusing an isonitrogenous amount of amino acids without glucose avoids hyperglycemia and, thus, accentuates the patient's anabolic response to feeding (study II).

In order to confirm the validity of our assumptions we will perform two consecutive studies in two distinct patient populations. For the assessment of the patients' catabolic state and obtaining insight into the biochemical mechanisms, whereby the effects of nutrition are mediated, stable isotope tracer kinetics will be applied. Using primed continuous infusions of L-[1-13C]leucine and [6,6-2H2]glucose we will quantitate the whole body dynamics of protein and glucose metabolism, i.e. protein breakdown, amino acid oxidation, protein synthesis, glucose production and glucose uptake before and after surgery. A positive protein balance (difference between protein synthesis and protein breakdown) will be used as an indicator of anabolism. Anabolic processes at the organ level (liver, muscle), i.e. fractional synthesis rates of the acute phase proteins albumin and fibrinogen and muscle protein synthesis will be determined using L-[2H5]phenylalanine infusions. Skeletal muscle protein catabolism will be characterized by measuring the mRNA expression of ubiquitin and two of its key ligases in muscle (MAFbx/atrogen-1 and MuRF-1).