Michel Roulet

Copper Metabolism and Requirements in Total Parenteral Nutrition

Copper metabolism and requirements in patients receiving total parenteral nutrition were studied in 28 patients with gastrointestinal diseases. During each of the 3 wk of the study period, each of 24 patients received in their total parenteral nutrition solutions, a daily dose of copper amounting to 0.25 mg, 1.05 mg, or 1.85 mg, in a random order. The other 4 patients received a fixed daily dose of 1 mg throughout the 3 wk. Increased losses of copper through the gastrointestinal tract occurred in patients with diarrhea or high-output stomas or fistulas. Patients with abnormalities of liver excretory functions had decreases in gastrointestinal copper losses. Urinary copper excretion was twice that of normal subjects. Copper infused in excess of the requirements was retained and not excreted. Plasma copper did not reflect the copper balance and cannot be used as a guide for copper supplementation. Copper requirements were found to be 0.3 mg/day in patients with normal amounts of gastrointestinal excretion. In the presence of diarrhea or increased fluid loss through gastrointestinal stomas or fistulas, the copper requirements for total parenteral nutrition are 0.4--0.5 mg/day.

A controlled trial of the effect of parenteral nutritional support on patients with respiratory failure and sepsis.

Energy and protein metabolism was studied in 11 septic patients receiving ventilatory support while on three different intravenous regimens. They received 5% dextrose in water (D5W), and one of two different regimens of parenteral nutritional support (PNS); either amino acid and dextrose (PNA) or amino acid and dextrose and lipid (PNB). All patients were given D5W and PNS in random order. The energy intake was targetted to exceed by 50% the measured metabolic rate. On D5W the mean measured energy expenditure was only 15.2% above the expected energy expenditure (p<0.02). A respiratory quotient of 0.75 while on D5W showed that in the absence of PNS the major part of energy requirements came from fat oxidation. In addition, on D5W these patients were in negative nitrogen and protein (synthesis-catabolism) balance. With PNS the metabolic rate rose significantly (p<0.02). While on PNA, the CO2 production was significantly higher than with PNB, and despite receiving all non-protein energy as glucose, the patients continued to oxidise fat to meet about 30% of their energy requirements. Continued fat oxidation was found to be associated with insulin resistance and high catecholamine levels, suggesting a cause and effect relationship. PNS caused an increase in protein (synthesis - catabolism) and nitrogen balances, and reduced leucine oxidation. The fall in leucine oxidation was greater on PNB than on PNA. Protein and nitrogen balances, expressed per gram of amino acid infused, were significantly better with PNB than PNA. It was concluded that insulin resistance may make fat an efficient source of energy.