Continuous tissue monitoring is enabled through the insertion of small Microdialysis catheters. A physiological salt solution is slowly constantly pumped through a semipermeable membrane and the solution is equilibrated with the surrounding tissue fluid.
The Microdialysis Catheter mimics a blood capillary. Substances from the extracellular fluid of the tissue diffuse across the membrane of the catheter into the perfusion fluid inside the catheter.
The main design resembles a concentric tube where the perfusion fluid enters through the space between an inner tube and the outer dialysis membrane; the perfusion fluid flows to its distal end and exits in the tube, It is between the inner tube and the mebrane where the “dialysis” takes place, i.e. the diffusion of molecules between the extra cellular fluid and the perfusion fluid.
Substances from the extracellular fluid diffuse through the membrane of the microdialysis catheter into the space between the inner tubing and the outer dialysis membrane, enter into the inner tube. The “microdialysate” is then collected in a microvial to be analyzed.
Microdialysis offers the opportunity to sample tissue chemistry with high accuracy and without taking any blood. The dialysate is extracted into small vials for bedside or laboratory analysis.
