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?
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.
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:
- 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)
- Removal of dialysable toxins, i.e. ones which aren’t very lipophilic or protein-bound
- Ethylene glycol
- 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