Total parenteral nutrition (TPN) after
trauma and
sepsis has two major goals. One is the reduction of enhanced
protein catabolism; the second is the avoidance of enhancement of whole-body
glucose turnover.
Glucose and
xylitol differ in their quantitative utilization rate after
trauma and
sepsis. Maximal
glucose utilization is reduced during such states, while the utilization of
xylitol is more than doubled. In order to investigate whether these differences are associated with beneficial effects with regard to whole-body
glucose turnover rate of gluconeogenesis and
protein sparing, we conducted two studies using animal models and two clinical studies. METHODS. For the determination of
glucose and
protein turnover, radioactive and stable
isotope techniques were applied. In an animal model a primed constant infusion of 3-H-6-glucose, 14-C-1-alanine and 13-C-3-alanine and 14-C-U-acetate was used to determine total
glucose appearance, gluconeogenesis from 3-C-precursors and
alanine flux. In the human studies hepatic
glucose production was determined by using a primed constant infusion of 6.6-D-2-glucose and
urea synthesis rate was determined by a primed constant infusion of 2-N-15-urea. RESULTS. In the first rat model we were able to show that hypocaloric
xylitol compared to
glucose significantly reduced whole-body
glucose turnover from 1741 +/- 232 mumol/h during
glucose infusion to 449 +/- 49 mumol/h during
xylitol infusion and gluconeogenesis from C-3 carbons form 382 +/- 24 mumol/h during
glucose infusion to 155 +/- 39 mumol/h during
xylitol infusion after a
burn trauma. In a second septic rat model the exchange of
glucose calories by
xylitol in a proportion of 1:1 was associated with a significantly ameliorated N-balance from +144 +/- 90 mgN/kg
body weight per day during
glucose infusion to +699 +/- 80 mgN/kg
body weight per day during
glucose-
xylitol infusion and a reduced 3-methyl-histidine excretion from 7.14 +/- 0.61 mumol/kg body wt. per day during
glucose infusion to 4.10 +/- 0.56 mumol/kg per day during
glucose-
xylitol infusion, respectively. In two studies with
surgical intensive care patients we were able to confirm the
nitrogen-sparing properties of
xylitol infusion, together with
amino acids during hypocaloric feeding or during TPN with a
glucose/
xylitol mixture in a proportion of 1:1. From a basal
urea production rate of 9.2 +/- 1.6 mumol/kg min.
xylitol led to a significant reduction with 6.4 +/- 1.5 mumol/kg per min. Hepatic
glucose production was significantly reduced during
xylitol infusion from basal 4.8 +/- 0.6 mg/kg per min to 3.1 +/- 0.7 mg/kg per min, respectively. Equicaloric
glucose in a dosage of 3 g/kg per day had no effect. During TPN
glucose/
xylitol, in a proportion of 1:1 at a total dosage of 0.24 g/kg per h, significantly reduced whole-body
glucose turnover, endogenous
glucose production and
lactate concentrations compared to an isocaloric
glucose infusion. DISCUSSION. In animal as well as in human studies hypocaloric
xylitol as well as a
glucose-
xylitol mixture were more efficient in preserving body
protein than
glucose alone. Whole-body
glucose turnover was significantly reduced during hypocaloric
xylitol or
glucose-
xylitol infusion compared to isocaloric
glucose infusion. During the acute phase after
trauma we therefore recommend a
carbohydrate supplementation of 3 g/kg body wt. per day using
xylitol. During long-term TPN, a
glucose-
xylitol mixture in a proportion of 1:1 in a dosage of 3 g/kg body wt. per day each is recommended as energy source, together with
amino acids and, if necessary,
lipids.