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)