Open flow microperfusion-interstitial sampling of large molecules

In this study the open flow microperfusion technique was used to sample interstitial fluid from the subcutaneous adipose tissue of 6 healthy volunteers during a 6-h fast. The system is based on a perforated double lumen catheter which is perfused by isotonic, ionfree perfusate. The collected samples were analysed for substances of different molecular weight (sodium, potassium, glucose, lactate and albumin). The results indicate that all considered substances could be sampled and measured during the whole study period. The sodium, potassium and lactate concentrations did not change (p<0.05 versus basal level) during the study. However, a significant decrease (p<0.05 vs. basal level) of the glucose and the albumin concentration were observed 3 hours and 1.5 hours after insertion of the catheter, respectively. In this study it could be shown that sampling of molecules even with a high molecular weight like albumin is possible. The gradual but slow decline of the glucose and albumin concentration in the sampled perfusate might be caused by drainage through the relatively high perfused catheter (4 μl·min^-1)