Background: Analyses of the distribution and elimination of glucose 2.5% solutions can be used to suggest combinations of infusion rates and infusion times which yield a predetermined plasma glucose level and degree of plasma dilution during surgery.
Methods: Twelve patients aged between 27 and 51 (mean 40) underwent laparoscopic cholecystectomy. An i.v. infusion of 1.4 litres of glucose 2.5% over 60 min was started when surgery began. A volume kinetic model was fitted to measurements of the plasma glucose concentration and the degree of haemodilution. Nomograms were constructed based on the kinetic results.
Results: The volume of distribution for the glucose and infused fluid and the plasma insulin levels were similar to the ones recorded in previous volunteer studies, but 50-70% lower values were obtained for the clearance of glucose (mean 0.21 litres min(-1)), endogenous glucose production (1.1 mmol min(-1)) and the elimination rate constant for the infused fluid (median 37 ml min(-1)). Urinary excretion was markedly depressed and amounted to 9% of the infused fluid volume 4 h after starting surgery. To prevent hyperglycaemia, nomograms suggested that the infusion should be directed towards a "target" glucose concentration and then slowed down in a controlled way. At steady state, the infused fluid maintains a 3.5% plasma dilution for each mmol that plasma glucose remains above baseline.
Conclusion: Metabolic changes warrant careful balancing of infusion rates of glucose 2.5% during laparoscopic cholecystectomy, which is facilitated by a nomogram. Volume expansion from the infused fluid volume should be recognized.