Question 2b

Highest mark
?
Pass rate
?
Other SAQs in this topic:
Other SAQs in this paper:

A seventy-six (76)  year  old  man  is  admitted  to  the  ICU  following  a  laparotomy  for  faecal peritonitis.  He has developed Multiple System Organ Failure over two days, requiring ventilatory and inotropic support.   He is oliguric, increasingly acidotic, uraemic and has a rising serum creatinine.

(b)       What would be your indication for renal dialysis in this man?

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College Answer

In this man, indications for renal replacement therapy/dialysis would include:
Uncontrolled electrolyte disturbances (eg. hyperkalaemia, hypernatraemia); uncontrolled metabolic acidosis (pH criteria depend on ventilatory response); uraemia (traditionally > 35 mmol/L, or ? creatinine  >  0.6  mmol/L);  complications  of  uraemia  (eg.  encephalopathy,  pericarditis);  fluid overload unresponsive to diuretics. Some units would consider early intervention (unproven) with specific techniques to minimise the inflammatory response to sepsis.

Discussion

This question closely resembles Question 8 from the second paper of 2005; "Outline  the clinical scenarios  in which you would consider  instituting dialysis in the critically ill.". In order to simplify revision, I reproduce the answer below:

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 or lactate (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 bishosphonates

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