[Limits of the extensive use of glucose as infusion carbohydrate in parenteral nutrition].

The limiting factors for parenteral nutrition with glucose are indicated by the metabolic states of the patients. The rate of glucose utilization is mainly restricted by the degree of insulin resistance which may be localized at the receptor (down regulation, tyrosine kinase?) or at the postreceptor (mediators? Randle-mechanism) level. Usually, clear data about the rate of glucose production in the liver and glucose utilization in the peripheral organs are lacking, and therefore the glucose infusion rate cannot be calculated individually. The glucose infusion rate is usually adapted by monitoring the glucose and insulin levels in the patients; furthermore, insulin-resistant states may be detected by these parameters. As glucose is a main energy source in parenteral nutrition, up to 500 mg glucose/kg B.W./h may be infused in addition to a recommended amount of amino acids and lipid emulsions. Permanent infusion of glucose (over 24 h) is metabolically not adequate, since permanent hyperglycemia and hyperinsulinemia may lead to lipid deposition in the liver. In insulin-resistant states with hyperglycemia glucose infusion rates are limited and should be carefully adapted. Under these circumstances, glucose may be partly replaced by xylitol and sorbitol. Still unanswered is the question of whether the limited glucose utilization rate should be increased by therapeutic interventions. The elimination of insulin-resistant states should be useful in the postaggression syndrome. This therapeutic regimen would also promote protein and lipid synthesis. Since insulin is a main anabolic hormone, its optimal action should be restored as soon as possible.