Perioperative metabolism in children. Studies of maintenance fluids, carbohydrate and fat metabolism during anaesthesia and cardiopulmonary bypass

Abstract

Perioperative fluid therapy is a cornerstone in paediatric anaesthesia. The high metabolic rate may make young children more susceptible for interrupted energy supply during surgery. Effects on glucose and fat metabolism related to perioperative fluid combinations with and without glucose and lipids during and after surgery were therefore studied using repeated blood samplings, arteriovenous differences and indirect calorimetry. Fluid with and without glucose was given to neonates (n=14) during major surgery. Glucose concentrations in blood were comparable regardless of fluid therapy. Without glucose increased free fatty acids and 3-hydroxybutyrate concentrations were seen. Hypoglycaemia and high 3-hydroxybutyrate concentrations occurred in an 11h old neonate after interruption of the preoperative glucose supply. When lipids were given in addition to glucose to neonates (n=12) immediately after major neonatal surgery, increased concentrations of triglycerides, free fatty acids and 3-hydroxybutyrate were found during 4-8 hours. Perioperative glucose concentrations were measured in infants and children (n=40) with four combinations of intra- and postoperative fluids mimicking possible clinical routines during minor surgery. No hypoglycaemia occurred. Glucose-containing fluid resulted in elevated glucose concentrations of short duration. In order to calculate RQ during infant surgery (n=18) VO2 and VCO2 were measured. RQ was lower without glucose administration, indicating less glucose oxidation. With glucose supply, a tendency to lower VO2 was seen. Infants and children (n=17), given fluid only as a blood-containing prime solution during hypothermic cardiac surgery, were studied with body and brain arteriovenous differences. The arterial glucose and lactate concentrations were influenced by the prime solution. Lactate elimination concomitant with glucose production and increased arterial ketone concentrations concomitant with increased cerebral arteriovenous ketone differences were found during rewarming.Conclusions: Glucose concentrations are maintained during paediatric surgery. Glucose administration results in increased glucose concentrations and higher glucose oxidation. Glucose interruption may cause hypoglycaemia in neonates. Without intraoperative glucose supply neonates mobilise fat. Immediate postoperative lipid administration to neonates is well tolerated. Glucose formed from gluconeogenesis and ketones from endogenously released fat are used as substrates by the brain during cardiac surgery with minimal glucose supply.