Abstract
The question of whether renal replacement therapy should be applied in an intermittent or continuous mode to the patient with acute kidney injury has been the topic of several controlled studies and meta-analyses. Although continuous renal replacement therapy (CRRT) has a theoretical advantage due to offering the opportunity to remove excess fluid more gradually, none of the several outcome studies that have been undertaken in the meanwhile was able to demonstrate its superiority over intermittent renal replacement therapy (IRRT). In the present article, therefore, questions are raised regarding which are the specific advantages of each strategy, and which are the specific populations that might benefit from their application. Although several advantages have been attributed to CRRT - especially more hemodynamic stability allowing more adequate fluid removal, better recovery of renal function, and more efficient removal of small and large metabolites - none of these could be adequately proven in controlled trials. CRRT is claimed to be better tolerated in combined acute liver and kidney failure and in acute brain injury. IRRT is more practical, flexible and cost-effective, allows the clinician to discontinue or to minimize anticoagulation with bleeding risks, and removes small solutes such as potassium more efficiently in acute life-threatening conditions. Sustained low-efficiency daily dialysis is a hybrid therapy combining most of the advantages of both options.
Highlights
Few topics in nephrology have been the subject of so many randomized controlled trials (RCTs), meta-analyses and reviews than that of extracorporeal renal replacement in acute kidney injury (AKI)
continuous renal replacement therapy (CRRT) originally applied a simple concept without pumps or technology
Whereas solute removal with intermittent renal replacement therapy (IRRT) at the origin essentially made use of diffusion – that is, gradientrelated molecule shifts in a liquid milieu from higher to lower concentration gradients – CRRT started as a convective strategy, driven by removal of solute-containing ultrafiltrate through large pores and its replacement by substitution fluid
Summary
Few topics in nephrology have been the subject of so many randomized controlled trials (RCTs), meta-analyses and reviews than that of extracorporeal renal replacement in acute kidney injury (AKI). Small solute removal in acute life-threatening conditions in general the adequacy of IRRT and CRRT depends on the actual conditions under which the modalities are applied, IRRT has a more efficient immediate effect than CRRT when small water-soluble compounds are to be removed in an acute lifethreatening condition because of the high blood and dialysate flows that can be achieved, resulting in a superior clearance and mass transfer per time unit [49] This is highly relevant for severe hyperkalemia, especially in the initiation phase of AKI and in patients with rhabdomyolysis, in whom potassium release from the compressed and necrotized muscle may last for several days [50]. Abbreviations AKI, acute kidney injury; CRRT, continuous renal replacement therapy; ICU, intensive care unit; IL, interleukin; IRRT, intermittent renal replacement therapy; RCT, randomized controlled trial; SLEDD, sustained low-efficiency daily dialysis; TNF, tumor necrosis factor.
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