Dialysis Technology

History and Development of Dialysis Technology

• Dialysis is a process where blood is separated from a crystalloid solution by a semipermeable membrane, allowing solute transport by diffusion from a higher to a lower concentration.
• Thomas Graham's 1854 paper "Osmotic Force" described separating substances using a semipermeable membrane and the direct relation between solute molecular weight and diffusion rate.
• John Jacob Abel's 1913 dialysis procedure used a collodion membrane and an anticoagulant derived from leech heads to prevent clotting.
• The first clinical dialysis procedure was performed by George Haas in 1924, and he made significant progress with the addition of a blood pump and the use of heparin as an anticoagulant.
• Willem Kolff, after World War II, built an artificial kidney using regenerated cellulose membrane and developed the rotating drum kidney; he dialyzed 15 patients between 1943 and 1944, with one surviving.
• Leonard Skeggs and Jack Leonards developed the flat plate dialyzer in 1947, which reduced blood volume and increased membrane surface area.
• Richard Stewart began the development of the hollow fiber dialyzer in 1956, which provided high-efficacy solute transport, low priming volume, and low resistance to blood flow.
• The hollow fiber dialyzer became commercially available in 1970 and is the most widely used type of dialyzer and ultrafiltrator currently.
• Ultrafiltration is achieved through the filtration of water across a semipermeable membrane using a hydrostatic pressure gradient, creating a solute concentration gradient between the blood and the ultrafiltrate side of the membrane.
• A semipermeable membrane has microscopic holes that only allow water and small molecular weight solutes to pass, resulting in a concentration of blood cells and large molecules on one side and water and small molecules on the other.
• Ultrafiltration removes plasma water or ultrafiltrate from the blood using a microporous membrane material commonly manufactured in a hollow fiber configuration.
• The process of ultrafiltration, also known as hemoconcentration, is based on the movement of water and solutes across a semipermeable membrane, equalizing concentrations in a process called convection.

Ultrafiltration and Hemoconcentration in Cardiopulmonary Bypass (CPB)

• Ultrafiltration during CPB is primarily used to remove excess water, concentrate cellular elements and proteins in the blood, and maintain the patient's plasma concentration of diffusible solutes.
• Continuous ultrafiltration during rewarming on CPB has been hypothesized to attenuate the inflammatory response, particularly during the peak of cytokine and complement levels.
• A balanced electrolyte solution can replace ultrafiltrate during rewarming to enable continuous ultrafiltration, potentially reducing the inflammatory response.
• Z-Buf, a form of ultrafiltration, has been used to correct hyperkalemia, particularly during cardiopulmonary bypass.
• Potassium loads during CPB, originating from potassium-based cardioplegia and red blood cells, can be effectively managed through ultrafiltration and replacement with a low-potassium solution.
• Z-Buf has also been used to correct severe electrolyte and acid-base disturbances in adults undergoing cardiac surgery, offering rapid corrections and the ability to select the concentration of diffusible solutes in the replacement fluid.
• Modified Ultrafiltration (MUF) has been described for pediatric patients, concentrating residual circuit blood for transfusion without the risk of hypervolemia, but requiring the patient to remain cannulated post-CPB.
• MUF can transfer nearly all circuit contents to the patient while the circuit remains primed with crystalloid solution, but protamine administration is contraindicated during MUF.
• Ultrafiltration can effectively remove direct thrombin inhibitors like bivalirudin, especially in patients with heparin-induced thrombocytopenia (HIT), a complication of heparin administration.
• Ultrafiltration can address challenges in managing hemodilution, electrolyte levels, and fluid shifts associated with the systemic inflammatory response during CPB.
• Z-Buf, when combined with MUF, has shown improved post-CPB outcomes and reduced levels of inflammatory mediators, demonstrating its potential clinical benefits.
• Ultrafiltration and dialysis, while serving similar functions in managing patient volume and electrolyte imbalances, have differences in efficiency in removing middle-molecule uremic solutes.