Why continuous Therapies? Continuous therapies closely mimic the GFR of native kidneys Large amounts of fluid and waste products removed over time Tolerated well by hemodynamically unstable patients.
Hemodialysis is for non-functioning kidneys in patients with fairly good health CRRT is for saving kidney function in patients with very poor health
CRRT Treatment Goals Maintain fluid, electrolyte & acid/base balances Prevent further damage to kidney tissue Promote healing and total renal recovery Allow other supportive measures; nutritional support
Access Internal Jugular Vein – Lower risk of complication Simplicity of catheter insertion Subclavian Vein – Higher risk of pneumo/hemothorax Associated with central venous stenosis Femoral Vein – Optimal site for immobilized patient Easiest site for infection Increased chance for infection
Filter clotting is the Achilles' heel of CRRT and causes hours of lost therapy. Heparin is often used and is effective but is not always feasible and requires monitoring of the ACT. Regional citrate anticoagulation minimizes the major complication of bleeding associated with heparin, but it requires monitoring of ionized calcium and calcium replacement. Pre-filter replacement fluid tends to dilute the blood entering the circuit and enhances filter longevity but decreases the efficiency of the process because of less filtrate available Filter Clotting
Constant pressure across the membrane causes a layer of protein to form over the membrane reducing its efficacy. This process is termed concentration polarization. Inflammatory mediators in septic patients adhere to the filter membrane also and contribute to clogging of the filter. Filter Clogging
Filter Pressure Drop is the change of pressure from blood entering the filter to that leaving the filter. It is a calculated value used to determine pressure conditions inside the hollow fibers of the filter. It will slowly rise with filter use as the hollow fibers become filled with microscopic clots. The amount and rate of increase determines the activation of the “filter is clotting alarm”.
Trans Membrane Pressure (TMP) is the pressure exerted on the filter membrane during operation of the PRISMA System. It reflects the pressure difference between the fluid and blood compartments of the filter. The permeability of the membrane decreases due to protein coating on the blood side of the membrane and adsorption of certain solutes. These processes cause clogging of the filter which causes the TMP to rise. The amount of increase and the rate of TMP increase contribute to the “Filter is Clotting” alarm.