Nitrogen and energy balance in depleted patients undergoing major gastrointestinal surgery: response to TPN

We studied energy and nitrogen balance during pre- and post-operative parental nutrition in 16 malnourished patients undergoing major abdominal surgery due to suspected gastrointestinal malignancy. The response to amino-acids alone (1.5g/kg; group AA) and energy alone (energy intake equal to pre-nutrition energy expenditure; group REE) was studied during the first day of pre- and post-operative nutrition. On the second day of parental nutrition both groups received amino-acids (1.5g/kg) and non-protein energy equal to pre-nutrition energy expenditure. Energy expenditure (EE) was increased both pre- and post-operatively (EE 112 +/- 15 and 121 +/- 14% of predicted, respectively). Nitrogen balance in group REE was more positive than in group AA on pre-operative day 2 (81.1 +/- 35.8 vs. 17.8 +/- 60.5 mg/kg; p < 0.05). N balance was better pre- than post-operatively on day 2 in both groups (17.8 +/- 60.5 vs. -49.6 +/- 49.2 mg/kg; group AA and 81.1 +/- 35.8 vs. 7.8 +/- 82.6 mg/kg; group REE; p < 0.05). Pre-operatively, administration of energy alone reduced EE (1489 +/- 301 vs. 1403 +/- 312 kcal/day; p < 0.05). We conclude that: 1) The patients were hypermetabolic both pre- and post-operatively. 2) Surgical trauma had a minor effect on EE. 3) Good nitrogen retention could be obtained both pre- and post-operatively at close to zero energy balance. 4) EE increased during the infusion of amino-acids more post-operatively than pre-operatively; non-protein energy at EE had no thermogenic effect. 5) Priming with energy improved nitrogen balance on the following day.