Why would you subject somebody to having their entire blood volume sucked out of their body and dragged though a fine filter? This is a favoured subject of the examiners. Previous questions on this topic include Question 16 from the second paper of 2011, Question 8 from the second paper of 2005, Question 6 from the second paper of 2003 and Question 2b from the second paper of 2001. Bellomo, in his chapter for Oh's Manual, lists the following "modern" indications for dialysis in the ICU:
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.
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.
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:
This is even less clear-cut. In many cases, it is possible to delay dialysis and make a series of medical and biochemical adjustments, with a resulting recovery of renal function. In a proportion of patients, RRT may be avoided altogether. The patients with the lower severity of illness may get away with just diuretics and medical management. This issues is explored in greater depth in the chaptert on the timing of renal replacement therapy.