The Dialyzer
There are three essential components to hemodialysis: the dialyzer, the composition and delivery of the dialysate, and The dialyzer consists of a plastic device with the facility to perfuse blood and dialysate compartments at ve surface area of modern dialysis membranes in adult patients is usually in the range of 1.5-2.0 m2. The hollow use in the
Recent advances have led to the development of many different types of membrane material. Broadly, there are four ca membranes: cellulose, substituted cellulose, cellulosynthetic, and synthetic. Over the past three decades, there has bee cellulose-derived to synthetic membranes, because the latter are more "biocompatible." Bioincompatibility is generally d membrane to activate the complement cascade. Cellulosic membranes are bioincompatible because of the presence of f membrane surface. In contrast, with the substituted cellulose membranes (e.g., cellulose acetate) or the cellulosyntheti groups are chemically bound to either acetate or tertiary amino groups, resulting in limited complement activation. Syn polysulfone, polymethylmethacrylate, and polyacrylonitrile membranes, are even more biocompatible because of the ab groups. Polysulfone membranes are now used in >60% of the dialysis treatments in the United States. Reprocessing and reuse of hemodialyzers are often employed for patients on maintenance hemodialysis in the United St manufacturing costs for disposable dialyzers have declined, more and more outpatient dialysis facilities are no longer re most centers employing reuse, only the dialyzer unit is reprocessed and reused, whereas in the developing world blood reused. The reprocessing procedure can be either manual or automated. It consists of the sequential rinsing of the bloo compartments with water, a chemical cleansing step with reverse ultrafiltration from the dialysate to the blood compart patency of the dialyzer, and, finally, disinfection of the dialyzer. Formaldehyde, peracetic acid-hydrogen peroxide, gluta all been used as reprocessing agents.
Dialysate
The potassium concentration of dialysate may be varied from 0 to 4 mmol/L depending on the predialysis plasma potass usual dialysate calcium concentration in U.S. hemodialysis centers is 1.25 mmol/L (2.5 meq/L), although modification m settings (e.g., higher dialysate calcium concentrations may be used in patients with hypocalcemia associated with secon or following parathyroidectomy). The usual dialysate sodium concentration is 140 mmol/L. Lower dialysate sodium conc with a higher frequency of hypotension, cramping, nausea, vomiting, fatigue, and dizziness. In patients who frequently their dialysis run, "sodium modeling" to counterbalance urea-related osmolar gradients is often used. When sodium mod concentration is gradually lowered from the range of 145-155 meq/L to isotonic concentrations (140 meq/L) near the e treatment, typically declining either in steps or in a linear or exponential fashion. Because patients are exposed to appro during each dialysis treatment, water used for the dialysate is subjected to filtration, softening, deionization, and, ultim During the reverse osmosis process, water is forced through a semipermeable membrane at very high pressure to remo contaminants and >90% of dissolved ions.
Blood Delivery System
The blood delivery system is composed of the extracorporeal circuit in the dialysis machine and the dialysis access. The of a blood pump, dialysis solution delivery system, and various safety monitors. The blood pump moves blood from the dialyzer, and back to the patient. The blood flow rate may range from 250-500 mL/min, depending largely on the type vascular access. Negative hydrostatic pressure on the dialysate side can be manipulated to achieve desirable fluid remo Dialysis membranes have different ultrafiltration coefficients (i.e., mL removed/min per mmHg) so that along with hydro removal can be varied. The dialysis solution delivery system dilutes the concentrated dialysate with water and monitors conductivity, and flow of dialysate.
