Microdialysis of the interstitial water space in human skin in vivo: quantitative measurement of cutaneous glucose concentrations

The purpose of this study was to evaluate the usefulness of a microdialysis technique for measurement of substances in the interstitial water space in intact human skin. Glucose was selected to validate the method. The cutaneous glucose concentration was measured by microdialysis and compared to that in venous blood. Single dialysis fibers (length 20 mm, 2,000 Da molecular weight cutoff) were glued to nylon tubings and inserted in forearm skin by means of a fine needle. Dialysis fibers were inserted in duplicate. Seven subjects were investigated after an overnight fast. Intradermal position of the dialysis probes was established by C-mode ultrasound scanning. The implantation trauma lasted 90-135 min as measured by laser Doppler flowmetry. Each dialysis fiber was calibrated in vivo by perfusing it with four to five different glucose concentrations. The perfusion rate was 3 microliters/min. Regression analysis of the calibration curves yielded the relative in vivo recovery of glucose. The skin glucose concentration was calculated as that particular perfusate glucose concentration that resulted in no net glucose transport across the dialysis membrane. Correlation coefficient of the regression lines was 0.93 +/- 0.03 (mean +/- SEM). After the injection trauma had vanished, recovery was 20.5 +/- 0.7%. Coefficient of variation (CV) on recovery was 10.9%. The cutaneous glucose concentration was 99.1 +/- 1.8% of the glucose concentration in venous plasma water (CV 4.1%). These findings suggest that the microdialysis technique accurately and precisely can reflect biochemical events in the interstitial water space in human skin in vivo.