hemodialysis

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hemodialysis

 [he″mo-di-al´ĭ-sis]
the use of principles of dialysis for removal of certain elements from the blood while it is being circulated outside the body in a hemodialyzer or through the peritoneal cavity (see peritoneal dialysis). The procedure is used to remove toxic wastes from the blood of a patient with acute or chronic renal failure. Called also dialysis, kidney dialysis, and renal dialysis. adj., adj hemodialyt´ic. 

Either the membrane lining the peritoneal cavity (in peritoneal dialysis) or a synthetic membrane (in extracorporeal hemodialysis) may be used as the dialyzing membrane. In the latter, the patient's blood is pumped from the arterial circulation through the hemodialyzer to the venous circulation. In the dialyzer, it flows past a cellulosic or synthetic semipermeable membrane while dialysate fluid flows past the other side of the membrane. Small molecules and ions diffuse through the membrane, passing from the side on which the concentration is higher to the side on which it is lower. The dialysate fluid contains no urea or creatinine, so that these constituents are removed at maximum rates. The concentrations of electrolytes are adjusted according to the needs of the patient. If the patient has hyperkalemia or hypernatremia, the excess ions of potassium or sodium are also removed. Other electrolytes are adjusted so that serum pH and electrolyte levels are not changed by the dialysis. Large molecules and blood cells cannot pass through the membrane and, therefore, stay in the blood.

Two commonly used accesses to the patient's vascular system are the external shunt and the internal arteriovenous (AV) fistula. An external shunt is usually indicated when dialysis must begin immediately. It requires two lengths of specially prepared tubing; one for insertion in a vein and the other in an artery, usually in the forearm. Between dialysis treatments, the tubes are joined by a connector. Although the external shunt has the advantage of being immediately available for use in an emergency, it has the potential of becoming infected or obstructed with clots, and, if the integrity of the system is disrupted, rapid and copious blood loss may occur.

The internal AV fistula is surgically created by anastomosing an artery to a vein; that is, the vein is arterialized or made into a large superficial vessel that is easily accessible by venipuncture. The fistula must heal gradually and become mature before a cannula can be inserted. When end-stage renal disease is inevitable, the fistula can be prepared months in advance for use when symptoms of uremia appear.
Patient Care. Hemodialysis treatments for chronic renal failure are usually done two to three times a week. The problems that a patient on hemodialysis may experience are fluid overload (hypervolemia), electrolyte imbalance, and alterations in blood components, leading to anemia or platelet abnormalities resulting in a tendency to bleed excessively. Another problem is infection, either of the access site and the blood or in the urinary or respiratory tract because of urinary or pulmonary stasis. Infection with human immunodeficiency virus is also a possibility since blood has not always been routinely screened for this virus and clients may have been infected. Precautions must be taken when handling any blood products or the dialysis equipment.

Patients who depend on hemodialysis to prolong their lives require extensive instruction in the care of their cannulae and access sites. Some individuals receive intensive training and are able to undergo hemodialysis at home. A partner must be trained in order to safely administer home hemodialysis. Follow up care, instruction, and evaluation by health care professionals are imperative to ensure patient safety.

Patients also must know about special precautions for avoiding the complications that accompany long-term hemodialysis. The purposes for prescribed medications should be explained, as well as side effects that should be reported. These drugs may include multivitamins, antacids, iron supplements, antihypertensives, digitalis, vasodilators, and antibiotics. Rigid dietary and fluid intake restrictions are particularly difficult for some patients and their families. Patient compliance can be a major challenge to caregivers who also must work with family members to help them deal with changes in sexual activities, role reversal, financial burdens, and encouragement of self-care and independence for the patient, balanced with as much support as necessary.

Additionally, caregivers should take time to examine their personal feelings and clarify their values in regard to patients' rights to treatment or refusal of it, and allowing patients to die with dignity.

Heparin is given before treatment is begun to patients who are to be treated by extracorporeal hemodialysis in order to prevent clotting of the blood during the procedure.
A hemodialysis circuit.

he·mo·di·al·y·sis

(hē'mō-dī-al'i-sis),
Dialysis of soluble substances and water from the blood by diffusion through a semipermeable membrane; separation of cellular elements and colloids from soluble substances is achieved by pore size in the membrane and rates of diffusion.

hemodialysis

/he·mo·di·al·y·sis/ (-di-al´ĭ-sis) removal of certain elements from the blood by virtue of the difference in rates of their diffusion through a semipermeable membrane while being circulated outside the body; the process involves both diffusion and ultrafiltration.

hemodialysis

(hē′mō-dī-ăl′ĭ-sĭs)
n. pl. hemodialy·ses (-sēz′)
A dialysis technique in which blood is removed from the body, filtered through a dialyzer that removes waste products and excess fluid, and then returned to the body.

hemodialysis

[hē′mōdī·al′isis, hem′-]
Etymology: Gk, haima + dia, apart, lysis, loosening
a procedure in which impurities or wastes are removed from the blood, used in treating patients with renal failure and various toxic conditions. The patient's blood is shunted from the body through a machine for diffusion and ultrafiltration and then returned to the patient's circulation. Hemodialysis requires access to the patient's bloodstream, a mechanism for the transport of the blood to and from the dialyzer, and a dialyzer. Also spelled haemodialysis. See arteriovenous fistula, external shunt.
method Access may be achieved by an external shunt or an arteriovenous fistula. The external shunt is constructed by inserting two cannulas through the skin into a large vein and a large artery. When hemodialysis is not being performed, the cannulas are joined, allowing the blood to flow from artery to vein. When hemodialysis is being performed, the cannulas are separated, allowing the arterial blood to flow to the dialyzer and the dialyzed blood to return from the dialyzer to the circulation through the cannula in the vein. An arteriovenous fistula is created by the anastomosis of a large vein to an artery. Large-bore needles are threaded into superficial vessels enlarged by the increased flow caused by the fistula. Various dialyzers may be used. Hemodialysis takes from 3 to 8 hours depending on the patient's condition, weight, and laboratory values and may be necessary daily in acute conditions or two to three times a week in chronic renal failure.
interventions A decrease in blood flow through the shunt may cause clotting. Therefore any factor that may result in a slowing of the flow should be avoided. Some of these factors are systemic hypotension, infection of the shunt or fistula, compression of the shunt or fistula, thrombophlebitis, and prolonged inflation of a blood pressure cuff. Infection is prevented in the area around an external shunt by placing a sterile dressing over the shunt and changing the dressing daily. Before the procedure is begun, the patient is told how long it will take, what pain or discomfort may be expected, what will be felt afterward, what food or activity will be allowed during the procedure, and whether family or friends may be present during treatment. Headache, nausea, and muscle cramps are common, especially during the procedure and for a few hours afterward. The patient usually feels best on the day after hemodialysis. Rest, an antiemetic, and a mild analgesic may make the procedure more comfortable. Most patients need emotional support and some physical assistance during hemodialysis. The physical status of the patient is monitored frequently throughout. Blood pressure, pulse, and blood tests for electrolyte and acid-base balance are performed. Normal saline solution may be administered to counteract hypotension that results from rapid removal of fluid from the intravascular compartment. The patient is weighed before and after the treatment to determine the amount of fluid lost during the procedure. An anticoagulant is usually given to prevent coagulation of the blood in the dialyzer, cannulas, or catheters. To prevent hemorrhage, protamine sulfate may be administered after the procedure to reverse the effect of the anticoagulant. Any treatment that causes tissue trauma, such as dental extraction, venipuncture, or intramuscular injection, is not recommended during or immediately after dialysis.
outcome criteria Infection and clotting of the shunt and erosion of the skin around the shunt are frequent complications with an external shunt; therefore the method that uses an arteriovenous fistula is more common. The discomfort before, during, and just after dialysis; the prolonged time of relative immobility during the procedure; and the dietary restrictions necessary in renal insufficiency all cause considerable stress in the patient. Adjustments in the patterns of daily life are necessary and require the assistance of professionals with experience and training.
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Hemodialysis

hemodialysis

 Nephrology A therapeutic procedure for removing low-molecular-weight toxins by allowing the blood to flow past a semipermeable membrane where the toxins diffuse away from the blood down a concentration gradient, either via an external AV shunt, or a surgically-placed AV fistula; hemodialysis is used in renal failure to ↓ BUN, creatinine, hyperkalemia and correct metabolic acidosis; prolonged dialysis results in a poor quality of life–anemia, infections, myalgia, peripheral neuropathy, cerebral edema, acute MI, aluminum toxicity, ergo renal transplants are always preferred to long-term hemodialysis Complications Pyogenic reactions due to gram-negative endotoxemia, with chills, fever, hypotension, nausea and myalgia, ↓ NK cell activity, ↓ serum calcitriol. See Dialysis dementia. Cf Hemapheresis.

he·mo·di·al·y·sis

(hē'mō-dī-al'i-sis)
Separation of soluble substances and water from the blood by diffusion through a semipermeable membrane; separation of cellular elements and colloids from soluble substances is achieved by pore size in the membrane and rates of diffusion.
Synonym(s): haemodialysis.

Hemodialysis

A method of mechanically cleansing the blood outside of the body, in order to remove various substances that would normally be cleared by the kidneys. Hemodialysis is used when an individual is in relative, or complete, kidney failure.

hemodialysis,

n mechanical process for removing waste products and impurities from the blood. Blood is drawn out and filtered through a dialysis machine and then reinfused. Often used in patients suffering from renal failure as well as other toxic blood conditions.
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Hemodialysis.

he·mo·di·al·y·sis

(hē'mō-dī-al'i-sis)
Dialysis of soluble substances and water from blood by diffusion through a semipermeable membrane.
Synonym(s): haemodialysis.

hemodialysis (hē´mōdīal´isis),

n a procedure in which impurities or wastes are removed from the blood. The patient's blood is shunted from the body through a machine for diffusion and ultrafiltration and returned to the patient's circulation. This procedure is used in treating renal failure and various toxic conditions. Without this, toxic wastes build up in the blood and tissues and cannot be filtered out by the ailing kidneys. This condition is known as uremia, which means “urine in the blood.” Eventually, this waste buildup leads to death. Dental treatment should occur within 24 hours of hemodialysis. See also kidney failure.

hemodialysis

removal of certain elements from the blood by virtue of difference in rates of their diffusion through a semipermeable membrane while the blood is being circulated outside the body. The procedure is used to remove toxic wastes from the blood of a patient with acute or chronic renal failure. See also kidney.
References in periodicals archive ?
The majority of my nursing career has been focused in nephrology nursing with the adult population--and has encompassed experiences in hemodialysis, home dialysis, peritoneal dialysis, and continuous therapies in the intensive care setting.
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