When healthy kidneys fail, serious complications arise: the body retains fluids and harmful wastes, blood pressure rises, and the body cannot make enough red blood cells. Hemodialysis is one treatment for kidney failure, in which a machine called a dialyzer, or filter, is used to clean the blood by filtering out wastes and extra fluids. It controls blood pressure and maintains the body's homeostasis, or proper balance of elements such as potassium sodium and chloride.