Intraoperative glucose administration influences respiratory quotient during paediatric anaesthesia

Background: Oxidation of carbohydrates and fat yields respiratory quotients (RQ) of 1.0 and 0.7 respectively. Maintained or increased blood glucose concentrations are usually seen during paediatric anaesthesia and surgery even without glucose administration. The aim of the present study tvas to evaluate whether an intraoperative glucose infusion influences the RQ as an indication of a different metabolic preference in comparison to a glucose-free fluid regime. Methods: Eighteen children between 0.5 and 24 months of age were studied during anaesthesia with controlled ventilation, oxygen in air,isoflurane, thiopentone, atracurium and fentanyl. Oxygen consumption and carbon dioxide production were measured using indirect calorimetry All children received Ringer acetate as needed; in addition, nine children were given glucose 10%, 3 ml kg(-1) h(-1), corresponding to 300 mg kg(-1) h(-1). Blood samples for analyses of glucose, lactate, free fatty acids and ketones were taken before and during surgery. Results: RQ was significantly higher in the children given glucose 0.92+/-0.08, compared to 0.81+/-0.06 in the children without glucose (P<0.01). Oxygen consumption tended to be higher, although not significantly so, in patients without glucose infusion. Energy expenditure was 1.70+/-0.29 kcal kg(-1) h(-1), without significant group differences. Higher blood glucose concentrations during surgery were found in the children given glucose. Conclusions: Our results indicate a higher glucose oxidation rate in patients given glucose during surgery.