The Effect on Energy and Nitrogen Metabolism by Continuous, Bolus, or Sequential Infusion of a Defined Total Parenteral Nutrition Formulation in Patients After Major Surgical Procedures

BACKGROUND: The role of IV infusion kinetics to explain nutrition efficiency was investigated in patients after major surgical procedures. METHODS: IV nutrition was provided as three different infusion kinetic regimens in a randomized fashion. All patients received nonprotein calories (100% of predicted preoperative REE, 60% D-glucose, 40% fat) and amino acid nitrogen (0.2 g N/d). Group A: Nutrition was provided by sequential infusion with combined fat and amino acids during daytime and glucose alone during nighttime ("sequential infusion"). Group B: Patients received 24-hour combined infusion with fat, amino acids, and glucose (all in one mixture) ("continuous infusion"). Group C: Nutrition was provided by bolus infusions during 1 hour followed by 2 hours without any infusion ("bolus infusion"). RESULTS: The daily energy balance was negative in all groups (-318 +/- 25 kcal/d, sequential infusion; -368 +/- 25 kcal/d continuous infusion; -292 +/- 20 kcal/d, bolus infusion). Significantly different excretion patterns of nitrogen in urine occurred among the groups despite an almost identical provision of nitrogen. Continuously infused patients retained nitrogen significantly better (-0.2 +/- 0.6 g/d) compared with sequentially (-3.4 +/- 1.0 g/d) and bolus-infused patients (-2.8 +/- 0.3 g/d) (p < .01), whereas their cumulative urinary glucose excretion was significantly larger. Continuously infused patients were in cumulative nitrogen balance during the entire postoperative period, whereas the other groups were in a significantly negative nitrogen balance. Urinary 3-methylhistidine excretion was similar in all groups. CONCLUSIONS: The breakdown of muscle proteins was not sensitive to alterations in nutrient and substrate supply. Thus improved nitrogen retention reflected entirely improved synthesis. "All-in-one" IV nutrition with prolonged infusion periods is at present the most favorable regimen considering both the nutritional efficiency and its metabolic load on the organism after major surgery.