Metabolic stress during hypoglycaemia clamp assessed by microdialysis

Aim. Microdialysis allows the biochemical analysis of interstitial fluids as a bedside procedure. This technique is of interest to evaluate the glucose dependant metabolism in hypoglycaemic patients. It was the aim to perform subcutaneous and blood microdialysis during hypoglycaemic clamp experiments in 12 healthy young men to reveal basis data for critical care microdialysis practice. Methods. The hyperinsulinaemic clamp was induced with a continuous infusion of 1.5 mU min^-1kg^-1 insulin (H-insulin, Hoechst, Frankfurt, Germany). A 20% dextrose solution simultaneously was infused at a variable rate to control blood glucose levels. For hypoglycaemia blood glucose levels were reduced to 40 mg/dL for a 30 min period. Glucose, lactate, pyruvate and glycerol concentrations were semicontinuously measured. Results. The absolute concentrations of glucose and glycerol in blood vs subcutaneous microdialysate were significant different during observation. Until the end of hypoglycaemia, glucose concentration in both compartments, declined in parallel, followed by an increase thereafter. During the clamp the subcutaneous glycerol increased threefold, where- as blood glycerol rose with a delay of 15 min and increased only twofold. After the clamp in both compartments glycerol values normalized. The lactate- pyruvate- ratio persisted in normal range throughout the examination. Conclusion. In our experiment subcutaneous lipolysis increased faster and more profound than blood microdialysis. We propose the microdialysis technique as an additional monitoring tool in hypoglycaemia patients.