FRUCTOSE VS GLUCOSE IN TOTAL PARENTERAL-N UTRITION OF CRITICALLY ILL PATIENTS

Parenteral nutrition required following surgery or injury should not o nly meet post-aggression caloric requirements but also match the speci fic metabolic needs so as not to worsen the metabolic disruptions alre ady present in this situation. The primary objective of parenteral nut rition is body protein maintenance or restoration by reduction of prot ein catabolism or promotion of protein synthesis or both. Whether all parenteral energy donors, i.e., glucose, fructose, other polyols, and lipid emulsions, are equally capable of achieving this objective conti nues to be a controversial issue. The objective of the present study w as to answer the following questions: (1) Do glucose and fructose diff er in their effects on the metabolic changes seen following surgery or injury, the changes in glucose metabolism in particular? (2) Can the observation of poorer glucose utilization in the presence of lipids be confirmed in ICU patients? Patients, materials and methods. A prospec tive, randomized clinical trial has been conducted in 20 aseptic surgi cal ICU patients to generate an objective database along these lines b y performing a detailed analysis of the metabolic responses to differe nt parenteral nutrition protocols. The effects of a glucose solution lipid emulsion regimen vs fructose solution + lipid emulsion regimen on a number of carbohydrate and lipid metabolism variables were evalua ted for an isocaloric (carbohydrates: 0.25 g/kg body weight/h; lipids: 0.166 g/kg body weight/h) and isonitrogenous (amino acids: 0.0625 g/k g body weight/h) total nutrient supply over a 10-h study period. Resul ts. A significantly smaller rise in blood glucose concentrations (incr ease from baseline: glucose + lipids P < 0.001 vs fructose + lipids n. s.) suggested that fructose had a small effect, if any at all, on gluc ose metabolism. Serum insulin activity showed significant differences as a function of carbohydrate regimen, i.e. infusion of fructose inste ad of glucose produced a less pronounced increase in insulin activity (increase from baseline: glucose + lipids P < 0.001 vs fructose/lipids P < 0.01). Impairment of glucose utilization by concomitant administr ation of lipids was observed neither in patients who first received gl ucose nor in those who first received fructose. Conclusions. As demons trated, parenteral fructose, unlike parenteral glucose, has a signific antly less adverse impact than glucose on the glucose balance, which i s disrupted initially in the post-aggression state. In addition, the l ess pronounced increase in insulin activity during fructose infusion t han during glucose infusion can be assumed to facilitate mobilization of endogenous lipid stores and lipid oxidation. Earlier workers pointe d out that any rise in free fatty acid and ketone body concentrations in the serum produces inhibition of muscular glucose uptake and oxidat ion, and of glycolysis. These findings were recorded in a rat model an d could not be confirmed in our post-aggression state patients receivi ng lipid doses commensurate with the usual clinical infusion rates. Th e serious complications that can result from hereditary fructose intol erance are completely avoidable if a cartful patient history is taken before the first parenteral use of fructose. If the patient or family members and close friends, are simply asked whether he/she can tolerat e fruit and sweet dishes, hereditary fructose intolerance can be ruled out beyond all reasonable doubt. Only in the extremely rare situation s in which it is not possible to question either the patient or any si gnificant other, a test dose will have to be administered to exclude f ructose intolerance. The benefits of fructose-specific metabolic effec ts reported in the literature and corroborated by the results of our o wn study suggest that fructose is an important nutrient that contribut es to metabolic stabilization, especially in the post-aggression phase and in septic patients. Hyperglycaemic states are largely prevented, and fewer patients require exogenous insulin, thus avoiding the freque ntly underestimated risk of hypoglycaemic states.