Dialysis

Dialysis is a means of preserving one's life. It is the act of an external machine performing the function of an internal organ. When the kidneys are no longer able to filter waste products from the body, concentrate urine, or preserve electrolytes (minerals in one's blood and body fluid that affect many important aspects of normal balance in the body), then an individual is said to be in kidney failure, or renal failure. Dialysis is a cure for renal failure for many individuals. There are two types of dialysis techniques: peritoneal dialysis and hemodialysis. Peritoneal dialysis works by circulating a solution through the fluids of the abdomen. Hemodialysis works by circulating one's blood through a special machine that contains special filters to remove waste products.

Renal failure occurs when the kidneys fail to excrete harmful waste products. This may occur suddenly, acutely, or over a period of time, chronically, which may eventually lead to or end-stage renal disease (ESRD), which is a complete dysfunction of the kidneys. The etiologies of the two disease process are vast ranging from hereditary disorders to lifestyle choices. Dialysis is a treatment modality typically used to treat chronic renal failure. Diabetes and hypertension are the two most common causes of chronic renal failure and ESRD.

Peritoneal dialysis involves the use of a catheter, a soft tube. The tube is used to fill the abdomen with a dialysis solution which contains dextrose, a sugar that will pull wastes and extra fluid from the blood into the abdominal cavity, where the solution is present. The dialysis solution and the waste products from the blood are then drained out of the body via the catheter. This process of filling the abdomen and then draining it is called an exchange and takes approximately 30 to 40 minutes. The process of allowing the solution to remain the abdomen is called the dwell time, which takes approximately four to six hours. A typical regimen consists of four exchanges a day each with a dwell time four to six hours.

Hemodialysis utilizes a dialysis machine. The patient's blood is sent to the machine through what is known as a vascular access. A vascular access is a means for blood to travel from the patient, to the machine, and back to the patient. An access is surgically constructed and consists of three different subtypes: primary AV fistula, synthetic AV graft (bridge graft), and a central venous catheter. A primary AV fistula is the preferred type of vascular access. A connection (fistula) is created between an artery (A) and a vein (V) usually in the lower arm under the skin. This allows the insertion of small needles into the fistula and the flow of blood to and from the machine. The second type of access is the synthetic AV graft, or bridge graft. This method is used when a patient's arteries or veins are not able to create a fistula. In this situation, a plastic tube, graft, is used to construct a connection between the artery and vein. This tube is placed under the skin and is used similarly to an AV fistula. The third type of access is a central venous catheter. This route is performed in a more acute setting, when dialysis must be done immediately and the patient is devoid of a fistula, a graft or if a patient presents with nonfunctioning AV fistulas or grafts. Access is accomplished through placing a tube into a large vein in the neck. After the blood is collected from the body, it undergoes transformations by the dialysis machine. The machine allows contact between the patient's blood and a solution called dialysate through a membrane, which is a special filter. On one side of the membrane is the dialysate and on the other is the patient's blood. The toxic substances present in the blood shift from the blood, where it is in high concentration, to the dialysate, where it is in lower concentration or not present. This equalizes the concentration of the various substances. This method is more efficient than the natural kidneys and thus treatment is only needed intermittently. A typical regimen would include three to four hour sessions, three times a week.

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