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Schematic of semipermeable membrane during hemodialysis, where blood is red, dialysing fluid is blue, and the membrane is yellow. Kidney dialysis (from Greek διάλυσις, dialysis, 'dissolution'; from διά, dia, 'through', and λύσις, lysis, 'loosening or splitting') is the process of removing excess water, solutes, and toxins from the blood in people whose kidneys can no longer ...
Hemodialysis, also spelled haemodialysis, or simply dialysis, is a process of filtering the blood of a person whose kidneys are not working normally. This type of dialysis achieves the extracorporeal removal of waste products such as creatinine and urea and free water from the blood when the kidneys are in a state of kidney failure .
This primarily occurs through maintenance of the extracellular fluid compartment, the size of which depends on the plasma sodium concentration. Renin is the first in a series of important chemical messengers that make up the renin–angiotensin system .
Dialysis may be instituted when approximately 85%–90% of kidney function is lost, as indicated by a glomerular filtration rate (GFR) of less than 15. Dialysis removes metabolic waste products as well as excess water and sodium (thereby contributing to regulating blood pressure); and maintains many chemical levels within the body.
Glomerular filtration rate (GFR) is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. [4] Central to the physiologic maintenance of GFR is the differential basal tone of the afferent (input) and efferent (output) arterioles (see diagram).
Catheter access, sometimes called a CVC (central venous catheter), consists of a plastic catheter with two lumens (or occasionally two separate catheters) which is inserted into a large vein (usually the vena cava, via the internal jugular vein or the femoral vein) to allow large flows of blood to be withdrawn from one lumen, to enter the dialysis circuit, and to be returned via the other lumen.
Treatment of chronic failure may include hemodialysis, peritoneal dialysis, or a kidney transplant. [2] Hemodialysis uses a machine to filter the blood outside the body. [2] In peritoneal dialysis specific fluid is placed into the abdominal cavity and then drained, with this process being repeated multiple times per day. [2]
Hemodialysis catheters are large diameter catheters (up to 16 French or 5.3mm) capable of flow rates of 200–300 ml/min, which is necessary to maintain the high flow rates of hemodialysis. There are two channels: one is used to carry the patient's blood to the dialysis machine, while the other is used to return blood back to the patient.