Description
Usually, additional medications to imitate kidney functions are needed for dialysis patients. Phosphate binders and erythropoiesis-stimulating substances fall under this category. Any medications a patient is taking should be evaluated because many medications rely on the kidneys for clearance and excretion. Due to the possibility of accumulation, the effects of dialysis are more substantial for medications used over an extended period of time; medications administered as a single or loading dosage hardly ever require adjustment.
Summary Listen
- Dialysis, derived from the Greek word meaning "dissolution," involves the movement of molecules across a semi-permeable membrane. Hemodialysis specifically refers to this process when it occurs in contact with blood using an artificial membrane. Thomas Graham first demonstrated solute movement across a semi-permeable membrane, while Avil and Rontri performed the first dialysis on dogs. The first human hemodialysis was performed by Dr. Haas, though it faced complications. Dr. John Paul created the first working dialysis machine, and Albert Kittley developed an improved model.
- To perform dialysis, an access point is required. Kittney's introduced the Schindler shunt, a metallic shunt placed between the radial artery and cephalic vein. Kimino and Bessia developed the Cimino-Brescia fistula, which is the surgical joining of an artery and vein. Indications for dialysis can be emergent, such as hyperkalemia or metabolic acidosis, or non-emergent, like persistent nausea or anorexia.
- The principles of dialysis include diffusion, convection, and ultrafiltration. Diffusion involves solute movement from high to low concentration. Convection involves solute movement due to fluid flow across the membrane. Ultrafiltration involves the removal of water. Hemofiltration, an advanced form of dialysis, utilizes convection to remove larger molecules. In peritoneal dialysis, osmosis is used via a catheter placed in the stomach, which then fills the peritoneum with a high dextrose concentration fluid.
- A hemodialysis machine comprises the dialysis solution, tubing for blood and solution transport, and a machine to power and monitor the process. Blood is drawn from an artery (or arterial port of a dialysis catheter) and returned to a vein (or venous port). The machine includes safety mechanisms such as pressure monitors and heparin injection. Dialyzers consist of hollow fibers with blood flowing in one compartment and dialysate flowing in the opposite direction, creating a counter-current flow.
- Dialysis membranes have evolved from cellulose-based to semi-synthetic cellulose, and now to synthetic polymers like polysulfone. Water used for dialysate must be highly pure, adhering to specific guidelines. A water treatment system includes backflow preventers, filters, water softeners, and reverse osmosis. Regular water quality testing is essential to prevent contamination and ensure patient safety.
- Adequacy of dialysis is assessed using parameters like urea reduction rate (URR) and Kt/V. The target URR is typically 65-70% for a single session, while the target Kt/V is 1.2 or greater for multiple sessions. A dialysis prescription includes factors like treatment duration, frequency, access type, membrane type, blood flow rates, dialysate flow rates, fluid removal volume, dialysate composition, and anti-coagulant dosage.
- Alternative dialysis methods include slow low-efficiency dialysis (SLED), used in hemodynamically unstable patients, and hemofiltration. Hemofiltration removes both small and middle molecules, potentially improving outcomes. Aquapheresis involves the removal of fluid only, and is often used for cardiac patients.
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About the Speakers
Dr Satyanarayana Garre
MBBS, MD, DNB( Nephrology) Apollo hospitals Hyderabad
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