Treatment with renal replacement therapy

In the majority of patients with severe ARF, residual renal function is so limited that renal replacement therapy becomes necessary to avoid complications and provide optimal levels of physiological support. Renal replacement therapy is now available in the form of continuous hemofiltration, intermittent hemodialysis, or peritoneal dialysis.

All these therapies have advantages and disadvantages. However, the use of peritoneal dialysis for the dialytic treatment of severe ARF in the ICU in developed countries is now uncommon. This is because standard peritoneal dialysis is associated with limited urea clearances, a high risk of peritonitis (> 15 per cent), and limited ability to maintain volume control.

Intermittent hemodialysis remains the most common form of renal replacement therapy in American ICUs, but in Europe it has been partially superseded by continuous hemofiltration. In Australia, continuous hemofiltration has almost completely superseded intermittent hemodialysis.

Traditional indications for starting renal replacement therapy (urea level > 35 mmol/l, fluid overload, pericarditis or other clinically important uremic complications, hyperkalemia, and severe metabolic acidosis) apply poorly to the intensive care environment where a more aggressive approach is advisable ( Table 1). The emerging philosophy of renal replacement therapy aims at preventing metabolic and cardiovascular derangements (maintaining homeostasis) rather than having to treat them.

Table 1 Austin and Repatriation Medical Center criteria for the initiation of renal replacement therapy in critically ill patients

The maintenance of fluid homeostasis in critically ill patients who receive significant amounts of nutritional support, blood, blood products, multiple medications, and variable amounts of resuscitation fluids becomes difficult even with the frequent use of hemodialysis. The rapid intravascular fluid and solute shifts associated with its application are poorly tolerated by such critically ill patients, particularly if cardiac dysfunction is present or the blood pressure requires support with vasopressor drugs. Under these circumstances, continuous hemofiltration techniques provide steady control of fluid balance, full and steady control of uremia, and easy maintenance of homeostasis. These features make them more suited to the intensive care environment even though their probable superiority is only supported by retrospective data ( Bellomo,, and Mehta 1995 )

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