Kidney international. Supplement
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Review
Is there a role for continuous renal replacement therapies in patients with liver and renal failure?
Continuous renal replacement therapy (CRRT) has now been in use for more than a decade in the management of patients with combined renal and hepatic failure. CRRT remains the treatment of choice in this group of critically ill patients because of improved cardiovascular and intracranial stability when compared with conventional intermittent hemofiltration and/or dialysis and effective solute clearances when compared with forms of peritoneal dialysis. ⋯ Whether continuous dialysis or hemofiltration is the mode of treatment choice remains unanswered, with greater amino acid and ammonia losses during dialysis, whereas hemofiltration leads to increased middle molecule and cytokine removal when compared with dialysis, the latter mainly caused by membrane adsorption. Whether the improved cardiovascular stability observed during these techniques is due to the removal of inflammatory mediators or is related to cooling as a consequence of the technique remains to be determined.
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There are many controversial results about the influence of acute renal failure (ARF) and renal replacement therapy (RRT) on patient outcome in intensive care units. This retrospective study compared demographics. severity, course, and prognosis of ARF during 36 months (period 1, 1991 through 1993; 128 cases) and 18 months (period 2, 1994 through 1995; 141 cases). Compared with period 1, during period 2 there was a markedly increased incidence of ARF. ⋯ Mortality in patients treated with CRRT was in period 1 and in period 2 higher than mortality in patients treated with intermittent RRT, but these results are biased by a preferred use of CRRT in severely ill patients with an unstable circulatory system. These data suggest that the early onset of RRT reduces the mortality of intensive care unit patients with ARF independent of underlying diseases. An influence of the method of RRT, sex, and age on outcome of patients with ARF could not be proven.
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Suppressed ex vivo endotoxin (ET)-induced production of the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), in isolated mononuclear cells (PBMCs) is associated with fatal outcome in severe sepsis. PBMCs from surviving patients, but not those from nonsurviving patients, recover their capacity to produce normal amounts of TNF-alpha. We tested the influence of two modalities of continuous renal replacement therapy (CRRT) on ex vivo-induced whole-blood production of TNF-alpha and inhibitory TNF-soluble receptor type I (TNFsRI) in 12 patients with acute renal failure and sepsis (APACHE II score 22 to 30). ⋯ These data suggest that high-volume CHFD is superior to standard CVVH in removing a suppressing factor of proinflammatory cytokine production. As CVVH only transiently improves TNF-alpha production, it is most likely that the putative suppressing factor is removed because of saturable membrane adsorption in CVVH. In CHFD, there is a combination of adsorption and detectable diffusion into the dialysate. It remains to be shown whether a further increase in the volume of dialysate per day is able to not only improve but normalize the cytokine response and improve outcome in septic patients with acute renal failure.
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While the use of hemofiltration to treat septic shock has potential benefits, the existing studies are difficult to compare because of their variety of inclusion criteria. The concept is to remove the various mediators of severe sepsis and septic shock, such as cytokines and eicosanoids, so that acute renal failure and the resultant multi-organ failure and possible death can be delayed or prevented. The dilemmas include: (a) hemofiltration cannot distinguish between these pro-inflammatory mediators as they are of similar molecular weights, and thus it is difficult to determine which one or combination should be eliminated for the best hemodynamics; (b) timing of the hemofiltration to remove a particular cytokine may make a difference in patient outcome; (c) the most efficacious convection rate of ultrafiltration has not been determined yet; (d) since these mediators quickly saturate the membrane, it should be frequently changed, and thus biocompatibility, availability and costs are added issues; (e) the choice of buffer is different according to the diagnosis of these critically ill patients. Before designing clinical trials, further experimentation is necessary to explore these problems.
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The anemia of renal failure is caused by the lack of sufficient quantities of endogenous erythropoietin. With the availability of recombinant human erythropoietin (rHuEPO), however, it has become apparent that to achieve a given target, hematocrit requires proper management of iron replacement, as well as the administration of rHuEPO. ⋯ Blood loss is less of a problem in patients on peritoneal dialysis, but poor iron intake and increased demand for iron are also seen, the latter in patients receiving rHuEPO. It is essential, therefore, for renal health professionals to understand iron metabolism in dialysis patients in order to properly balance the therapy of renal anemia with rHuEPO and supplemental iron.