Haemodialysis: From Basics to Bedside

Chronic kidney disease is a progressive loss of renal function that may lead to kidney failure. Kidney transplantation is the gold standard of kidney replacement therapy. Haemodialysis and peritoneal dialysis remain the alternative replacement therapies, where haemodialysis is the predominant dialysis modality globally. Haemodialysis is a supportive therapy that purifies blood from accumulated uremic toxins, removing excess fluids, and maintaining electrolytes and acid-base balance. It's usually conducted over 4 hours three times per week in a hospital-based unit, but it can also be performed in satellite units or at home. There are three combined physiological mechanisms in performing haemodialysis therapy. These are diffusion, ultrafiltration, and convection. Performing haemodialysis requires haemodialysis machine, dialyzer (membrane or filter), fistula needles, blood lines, buffers and electrolytes, vascular access, and treated water. Conventional haemodialysis is performed by using low-flux or high-flux dialyzers. This modality of dialysis, though supportive, has limited capacity in clearing large-size uremic toxins, which have been associated with inflammation, atherosclerosis and vascular calcifications, as well as poor quality of life and increased risk of morbidity and mortality. Recent haemodialysis modalities are empowered with effective convection to remove larger molecules. These advanced modalities include online haemodiafiltration and expanded haemodialysis, both of which are safe, efficient, and have been associated with increased survival rate and improved quality of life. This article reviews the basic physiological principles of conventional haemodialysis, its components, prescription, dialysis adequacy, anticoagulation, anticoagulation sparing strategies, and medications prescription. It also reviews the advanced haemodialysis modalities and compares their clinical outcomes with conventional haemodialysis.