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Overview of Renal Replacement Therapy

by James I. McMillan, MD

Renal replacement therapy (RRT) replaces nonendocrine kidney function in patients with renal failure and is occasionally used for some forms of poisoning. Techniques include intermittent hemodialysis, continuous hemofiltration and hemodialysis, and peritoneal dialysis. All modalities exchange solute and remove fluid from the blood, using dialysis and filtration across permeable membranes.

RRT does not correct the endocrine abnormalities (decreased erythropoietin and 1,25-dihydroxyvitamin D 3 production) of renal failure. During dialysis, serum solute (eg, Na, Cl, K, HCO 3 , Ca, Mg, phosphate, urea, creatinine, uric acid) diffuses passively between fluid compartments down a concentration gradient (diffusive transport). During filtration, serum water passes between compartments down a hydrostatic pressure gradient, dragging solute with it (convective transport). The two processes are often used in combination (hemodiafiltration). Hemoperfusion is a rarely used technique that removes toxins by flowing blood over a bed of adsorbent material (usually a resin compound or charcoal).

Dialysis and filtration can be done intermittently or continuously. Continuous therapy is used exclusively for acute kidney injury. Continuous therapy is sometimes better tolerated than intermittent therapy in unstable patients because solute and water are removed more slowly. All forms of RRT except peritoneal dialysis require vascular access; continuous techniques require a direct arteriovenous or venovenous circuit.

The choice of technique depends on multiple factors, including the primary need (eg, solute or water removal or both), underlying indication (eg, acute or chronic kidney failure, poisoning), vascular access, hemodynamic stability, availability, local expertise, and patient preference and capability (eg, for home dialysis). Indications and Contraindications to Common Renal Replacement Therapies lists indications and contraindications for the common forms of RRT.

Indications and Contraindications to Common Renal Replacement Therapies

Renal Replacement Therapy

Indications

Contraindications

Hemodialysis

Renal insufficiency or failure (acute or chronic) with any of the following that cannot otherwise be controlled:

  • Fluid overload (including refractory heart failure)

  • Hyperkalemia

  • Hypercalcemia

  • Metabolic acidosis

  • Pericarditis

  • Uremic symptoms

  • GFR* < 10 mL/min/1.73 m 2 BSA (chronic kidney disease, no diabetes)

  • GFR* < 15 mL/min/1.73 m 2 BSA (chronic kidney disease, diabetes)

  • Some poisonings (see Poisoning)

Uncooperative or hemodynamically unstable patient

Peritoneal dialysis

Same indications as for hemodialysis (except for poisonings) in patients who

  • Have inadequate vascular access

    or

  • Prefer self-therapy

Absolute:

  • Loss of peritoneal function

  • Adhesions that limit dialysate flow

  • Recent abdominal wounds

  • Abdominal fistulas

  • Abdominal wall defects that prevent effective dialysis or increase infection risk (eg, irreparable inguinal or diaphragmatic hernia, bladder extrophy)

  • Patient’s condition not amenable to dialysis

Relative:

  • Abdominal wall infection

  • Frequent episodes of diverticulitis

  • Inability to tolerate large volumes of peritoneal dialysate

  • Inflammatory bowel disease

  • Ischemic colitis

  • Morbid obesity

  • Peritoneal leaks

  • Severe undernutrition

Hemoperfusion

Poisoning or toxicity (eg, due to barbiturates, many antidepressants, ethchlorvynol, meprobamate, paraquat, glutethimide, metals such as lithium and barium, or toxic doses of aminoglycosides or cardiovascular drugs)

Uncooperative or hemodynamically unstable patient

*For calculation of GFR, see GFR.

Care of patients requiring long-term RRT ideally involves a nephrologist, a psychiatrist, a social worker, a renal dietitian, dialysis nurses, a vascular surgeon (or other surgeon skilled in peritoneal dialysis catheter placement), and the transplant surgical team. Patient assessment should begin when end-stage renal failure is anticipated but before RRT is needed, so that care can be coordinated and patients can be educated about their options, evaluated for resources and needs, and have vascular access created.

Psychosocial evaluation is important because RRT makes patients socially and emotionally vulnerable. It interrupts routine work, school, and leisure activities; creates anger, frustration, tension, and guilt surrounding dependency; and alters body image because of reduced physical energy, loss of or change in sexual function, changed appearance due to access surgery, dialysis catheter placement, needle marks, bone disease, or other physical deterioration. Some patients react to these feelings by nonadherence or by being uncooperative with the treatment team. Personality traits that improve prognosis for successful long-term adjustment include adaptability, independence, self-control, tolerance for frustration, and optimism. Emotional stability, family encouragement, consistent treatment team support, and patient and family participation in decision making are also important. Programs that encourage patient independence and maximal resumption of former life interests are more successful in decreasing psychosocial problems.

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