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Renal replacement therapy: Patient selection

Generally speaking, renal replacement therapy is necessary to prevent either fluid overload or endogenous poisoning.

Indications for starting renal replacement therapy:

  • Oliguria (urine output <200mL/12h)
  • Anuria/extreme oliguria (urine output <50mL/12h)
  • Hyperkalemia ([K]>6.5mEq/L)
  • Severe acidemia (pH<7.1)
  • Azotemia ([urea]>30mg/dL)
  • Clinically significant organ (especially pulmonary) edema
  • Uremic encephalopathy, pericarditis, or neuropathy/myopathy
  • Severe hypo- or hypernatremia ([Na]<115 or >160mEq/L)
  • Hyperthermia
  • Drug overdose with toxin that is able to be dialyzed

Modes of dialysis and ultrafiltration available:

  • Intermittent hemodialysis (acute renal failure patients, depending on how critically ill the patient is)
    • Most efficient because large amounts of fluid can be removed and electrolyte abnormalities can rapidly be corrected
    • Not appropriate in unstable patients, as 20-30% of patients undergoing hemodialysis will become hypotensive
    • In an unstable patient, the hypotension may not be tolerated and could cause further renal injury or disequilibrium syndrome from the large osmotic shifts
  • Peritoneal dialysis (chronis renal failure patients)
    • Simple and cost effective
    • Can cause infection, has poor clearance of solutes and uric acid
  • Continuous hemodiafiltration (acute renal failure in most ICU patients)
    • More effective urea clearance and controlled fluid removal
    • Beneficial in the critically ill patient, as these patients usually have intravascular hypovolemia secondary to decreased oncotic pressure from capillary leak, and this method allows for precise volume control, continuously.
    • Provides improved nutritional support
    • Safer in patients with cerebral injury or cardiovascular disorders, given the improved control of volume (prevent disequilibrium disorder or CHF, respectively)