Bellomo, in his chapter for Oh's Manual, lists the following "modern" indications for dialysis in the ICU:

  • Oliguria (less than 200ml in 12 hours)
  • Anuria (0-50ml in 12 hours)
  • Urea over 35 mmol/L
  • Creatinine over 400mmol/L
  • Potassium over 6.5mmol/L
  • Refractory pulmonary oedema
  • Metabolic acidosis with pH less than 7.10
  • Hypernatremia over 160mmol/L
  • Hyponatremia under 110 mmol/L
  • Temperature over 40°C
  • Complications of uraemia: encephalopathy, pericarditis, myopathy or neuropathy
  • Overdose with a dialysable toxin

It is possible to expand upon this list, but it would be impossible to improve upon its brevity, which is the quality of greatest worth to the time-poor exam candidate.

One should probably internalise this table, given how likely Bellomo is to have written many of the renal questions in the exam.

ADQI recommendations for the commencement of dialysis

Renal Indications
      • Oliguria with volume overload
      • Oliguria is relative; urine output may be high and still inadequate in clearing the fluid.
      • Uremia with symptoms
      • Hyperkalemia ( K+ over 6.0)
      • Metabolic acidosis due to renal failure (pH < 7.2)
Non-renal Indications
      • Removal of dialysable toxins, i.e. ones which aren’t very lipophilic or protein-bound
        • Lithium
        • Methanol
        • Ethylene glycol
        • Salicylates
        • Theophylline
        • Valproate
        • Pretty much any drug with a volume of distribution less than 0.5L/kg

          If a toxin is equally well cleared by hemodialysis and hemoperfusion, then hemodialysis is preferred, because it will also correct any underlying acid-base disturbance.

      • Removal of contrast agent
        • More relevant with old-school high-osmolar contrast
      • Clearance of cytokines to decrease severity of sepsis
        • Still controversial. May be of use in patients with renal failure and sepsis.
        • No evidence that it helps in patients with sepsis who don’t have renal failure.
      • Control of body temperature
        • An extracorporeal circuit can help control hypo or hyperthermia which is resistant to other methods of control.
      • Control of otherwise uncontrollable electrolytes
        • Hypercalcemia refractory to pamidronate, for one example.

When to start dialysis

For people looking after patients longitudinally, the greater skill is knowing when to start the maintenance dialysis early, and knowing when one can safely wait. The timing of RRT is a matter of some debate. The IDEAL trial of 2010 compared early and late starters, and concluded that there was no mortality difference. This influenced some changes to the original 2002 European guidelines.

The indications for maintenance dialysis according to these changes are as follows:

  • Start when the GFR has fallen to below 15ml/min
  • Definitely start before the GFR falls to below 6ml/min
  • Symptomatic uremia
  • Inability to control fluid balance
  • Inability to control blood pressure
  • Progressive deterioration in nutritional status
  • Diabetics may benefit from an earlier start
 
Renal Indications
      • Oliguria with volume overload
      • Oliguria is relative; urine output may be high and still inadequate in clearing the fluid.
      • Uremia with symptoms
      • Hyperkalemia ( K+ over 6.0)
      • Metabolic acidosis due to renal failure (pH < 7.2)
Non-renal Indications
      • Removal of dialysable toxins, i.e. ones which aren’t very lipophilic or protein-bound
        • Lithium
        • Methanol
        • Ethylene glycol
        • Salicylates
        • Theophylline
        • Valproate
        • Pretty much any drug with a volume of distribution less than 0.5L/kg

          If a toxin is equally well cleared by hemodialysis and hemoperfusion, then hemodialysis is preferred, because it will also correct any underlying acid-base disturbance.

      • Removal of contrast agent
        • More relevant with old-school high-osmolar contrast
      • Clearance of cytokines to decrease severity of sepsis
        • Still controversial. May be of use in patients with renal failure and sepsis.
        • No evidence that it helps in patients with sepsis who don’t have renal failure.
      • Control of body temperature
        • An extracorporeal circuit can help control hypo or hyperthermia which is resistant to other methods of control.
      • Control of otherwise uncontrollable electrolytes
        • Hypercalcemia refractory to pamidronate, for one example.

When to start renal replacement therapy?

Here, we have consensus failure. No agreement exists. A large task force couldn’t come up with anything more coherent than “start dialysis when the kidney failure is symptomatic”.

      • Let the RIFLE criteria be your guide: treatment to start somewhere between I and F
      • Stage I = urine output < 0.5ml/hr for over 12 hrs; serum creatinine has doubled from baseline
      • Stage F = urine output < 0.5ml/hr for over 12 hrs; serum creatinine has tripled from baseline

 The reason being, at stage F you end up with 3 to 10 times increased mortality among ICU patients.   

  •  

When to STOP renal replacement therapy?

  • Once again, no consensus exists.
  • Let us say, when the indication for CRRT has resolved; its similar to the criteria for extubation.
  • One large study used creatinine clearance of 12-20ml/min once urine volume is above 30ml/hr.

References

For a definitive treatment of all of this, you ought to pay homage to the gigantic and all-encompassing "Critical Care Nephrology" by Ronco Bellomo and Kellum (2009).

The Gambro and Fresenius websites have also been an excellent source of information.