AOHS Foundations of Anatomy and Physiology II Lesson

AOHS Foundations of Anatomy and Physiology II Lesson 19 Hemodialysis Copyright © 2014‒ 2016 NAF. All rights reserved.

By the end of this presentation you will know: • What a hemodialysis machine does • How a hemodialysis machine mimics the function of the kidneys • What a hemodialysis machine can’t do that the kidneys can • How a patient is connected to a hemodialysis machine

Hemodialysis is the process of cleaning a patient’s blood with a machine During hemodialysis, a patient’s blood circulates outside of his or her body, through a filter that acts as an artificial kidney. The first hemodialysis was performed in 1924. A modern hemodialysis machine Dr. John Merrill, who later performed the first kidney transplant, shows a then new “artificial kidney” to a patient.

Inside the dialyzer are hollow parallel fibers made of a semipermeable membrane The dialyzer membrane allows ions, urea, and other waste products to pass through, but it retains blood cells and proteins. What part of the nephron does this membrane resemble?

Blood flows into the dialyzer from one direction, and dialysate flows in from the other Dialysate is a solution that resembles the liquid part of plasma. A dialysis professional can adjust the composition of the dialysate based on the patient’s specific needs. What would happen if the dialysate were just water?

As blood flows through the fibers, ions and waste products diffuse into the dialysate Ions and waste products diffuse across the fibers’ semipermeable membranes. This diffusion occurs because concentrations are higher in the blood than in the dialysate. What are some substances you would expect to find in the dialysate?

Hemodialysis patients use a surgically altered vein, or access, to provide blood for dialysis A surgeon will connect an artery to the vein that will be used for dialysis. This connection makes blood flow more quickly through the vein. The most common type of access is called a fistula, where the vein and artery are sewn together.

Before dialysis, needles are put into two points just past the fistula Blood goes from the arterial port to the dialyzer. Blood returns to the body via the venous port, which is always “upstream” from the arterial port.

During dialysis, blood passes through a circuit outside the body

Hemodialysis patients usually need treatments three times a week Each treatment takes three to four hours. Many patients go to a dialysis clinic, but others can do dialysis at home with a trained family member or friend.

Dialysis is effective, but it’s not without side effects and risks Dialysis patients are often on blood thinners. These drugs make dialysis easier but increase the risk of excessive bleeding. The access points where needles go into the vein can also easily become infected. Serious infection can spread to the blood. How serious are these risks compared to the benefits of dialysis?

Heart disease and diabetes are the cause of 75% of newly diagnosed kidney disease While dialysis is a substitute for your kidneys, no machine can match the efficiency and thoroughness of the real thing. All the things you do to fend off heart disease and diabetes will also lower your risk of kidney disease. What are some specific things you can do to lower your risk of kidney disease?