CRRT临床应用治疗简介【培训课件】.ppt

* As mentioned earlier, replacement fluids may be administered pre or post filter. Pre-filter replacement fluids are often referred to as “pre-dilutional” fluids. Pre-dilution fluids are used to dilute the blood prior to entering the filter so that the blood HCT is lower. The benefit of pre-dilution is the prevention of hemoconcentration and reduction of filter clotting. Hemoconcentration occurs when too much plasma water is removed from the blood causing it to “thicken” and clot. In order to maintain precise fluid balance, the amount of pre-dilution replacement fluid is removed from the EC circuit by ultrafiltration. Therefore some of the replacement fluid is immediately removed. The question becomes then, how much is removed? It is difficult to say. Some people say 10-15%. The more fluid replacement infused and removed, the better the convective clearance of small and middle molecules. * Post dilution fluid replacement ensures that the patient receives the total electrolyte/buffer concentration contained in the fluid. As with Pre-dilution administration of replacement solution, the volume of fluid used is what drives the convective clearance. The benefits received from pre-dilution replacement are not present with post-dilution replacement. Therefore there may be a need to increase anticoagulation to prevent filter clotting. A benefit that post-dilution replacement fluid does offer is that the effluent (UF) chemistries truly reflect the plasma solute losses and thus filter efficiencies. The UF vs. plasma chemistry value is an important measure of filter efficiency. (Discuss FUN/BUN ratios if desired.) * In the schematic we can see how solutes travel from the high concentration of the blood side into the low concentration of the dialysate side. Dialysate prescription is adjusted to preserve necessary components and remove unwanted metabolites. Note that dialysate flow is established counter-current to the blood flow. This serves to increase effecti