Continuous renal replacement therapies: an update

Continuous renal replacement modalities have found widespread use and acceptance over the last decade. The various modalities differ in the kind of access (arteriovenous v venovenous); in the application of convective clearance (continuous hemofiltration), diffusive clearance (continuous hemodialysis), or a combination of both (continuous hemodiafiltration); and in the location where the replacement fluid enters the circuit (predilution v postdilution). Continuous therapies incorporate several advantages, such as improved hemodynamic stability, the possibility for unlimited alimentation, optimal fluid balance, and gradual urea removal without fluctuations. However, it has not yet been shown whether these advantages have a significant impact on outcome and prognosis, the ultimate measure of treatment efficiency. Major disadvantages of continuous therapies are the ongoing necessity for continuous anticoagulation, immobilization of the patient, and possible side effects from lactate-containing replacement fluid or dialysate. Continuous renal replacement procedures have certainly made the management of critically ill patients easier. In particular, oligoanuric patients with diuretic resistant volume overload and hemodynamically unstable patients with acute renal failure and concomitant sepsis or multiorgan failure appear to benefit most from continuous treatment. The role of continuous hemofiltration as a method of removing serum cytokines in septic patients without renal failure is still controversial and needs further clinical assessment. Due to slow efficacy, continuous renal replacement is indicated only in rare circumstances for intoxication; this therapy also is of rather limited use in severe hyperkalemia or acidosis. Noncritically ill patients with uncomplicated renal failure (eg, due to the use of dye or antibiotics) should be treated with intermittent hemodialysis or peritoneal dialysis. Furthermore, intermittent hemodialysis is preferable in patients with hemorrhagic diathesis because it can be easily performed without anticoagulants.