No Superiority for Dialysis Treatments in Acute Renal FailureEDMONTON, Alberta, Feb. 19 -- With acute renal failure, intermittent dialysis and continuous renal replacement both lead to the same end, according to a systematic review.
Action Points
* Explain to interested patients that for patients with acute renal failure, no difference in survival was found for two types of renal replacement therapy (four hours every-other-day versus continuous therapy).
* For stable patients, the researchers suggested that every-other-day, four-hour treatment might be sufficient.
There was also no indication that either method was superior for reducing the need for chronic dialysis, implying end-stage renal disease, in survivors, Marcello Tonelli, M.D., of the University of Alberta, and colleagues in the Alberta Kidney Disease Network, reported in the Feb. 20 issue of the Journal of the American Medical Association.
Diverse options are available for prescribing acute renal replacement therapy, including intermittent, continuous, and extended-duration hemodialysis and hemofiltration, and combinations. Yet questions remain about how best to provide renal replacement for these high-risk patients, Dr. Tonelli said.
Among the primary renal replacement therapies studied were intermittent hemodialysis (typically four hours, three times a week) and continuous renal replacement therapy (approximately 24 hours a day through arteriovenous or venovenous access).
The continuous method uses much slower rates of blood flow compared with intermittent hemodialysis and is typically delivered in an intensive care setting.
While fluid is used more slowly in the continuous method, it requires continuous anticoagulation, creating the potential for bleeding, while the lengthy exposure to an extracorporeal circuit increases the depletion of nutrients or adds to the infection risk.
Other methods, all submodalities of continuous therapy, are continuous venovenous hemofiltration, continuous venovenous hemodialysis, and continuous venovenous hemodiafiltration, the researchers noted.
The findings came from a search of Medline, Embase, and All EBM Reviews for prospective cohort studies and randomized controlled trials though October 2007. From 173 articles, 30 randomized controlled trials and eight prospective cohort studies were eligible.
Data from nine randomized controlled trials comparing continuous renal replacement therapy with intermittent dialysis indicated no clinically relevant difference between modalities, including all-cause mortality (relative risk 1.10, 95% confidence interval 0.99 to 1.23, I2=0.0%), the researchers wrote.
Data from a subset of these trials (five trials, 308 participants) suggested no significant difference in the frequency with which chronic dialysis was required for survivors (RR 0.91, 95% CI 0.56 to 1.49, I2=0.0%).
Although cohort data suggested a lower risk of hypotension in the continuous-therapy patients, this finding was not confirmed by the data within the available randomized trials, the researchers said.
For patients treated with continuous therapy, limited data suggest that bicarbonate may be preferable to other forms of dialysate alkali and that citrate infusion may be an alternative to systemic anticoagulation in patients at high risk of bleeding.
Among patients treated with the submodality, continuous venovenous hemofiltration, the risk of death was lower at doses of 35 mL/kg per hour (RR of death compared with doses of 20 mL/kg per hour 0.74, 95% CI 0.63 to 0.88). If this method is used, a dose of 35 mL/kg per hour should be provided, the researchers advised.
The use of unsubstituted cellulosic membranes should be avoided in intermittent hemodialysis (RR of death compared with biocompatible membranes 1.23, 95% CI 1.01 to 1.50), the investigators reported.
There was no evidence that either intermittent hemodialysis or continuous renal replacement therapy was superior in reducing resource use -- equipment and staff -- or the risk of requiring high-cost although infrequent chronic dialysis.
However, the researchers noted that the cost of providing therapy, considerably higher for continuous therapy, is small compared with the large cost of the index hospitalization and beyond. Thus, they said, relatively costly interventions may be attractive if they improve these longer-term outcomes.
Despite the wide variety of techniques available, uncertainty remains about when replacement therapy should be started and how long treatment should continue, in addition to the lack of a common metric for defining acute renal failure, the researchers said.
The decision to start renal replacement therapy in patients with severe illness requires assessment of intravascular volume, electrolyte and acid-base status, uremia, nutritional requirements, urine output, hemodynamic status, and the evolving clinical course of each patient, the researchers said.
Potential advantages of starting therapy earlier must be set against the hypothetical risks of treatment-induced renal injury, bleeding due to anticoagulation, and mechanical and infectious complications associated with central venous access, they noted.
Given the significantly higher cost of continuous renal replacement, intermittent alternate-day dialysis of four or more hours may be preferable for otherwise stable patients, they said.
More frequent dialysis may be required for highly catabolic patients or to achieve treatment targets for fluid, electrolyte, or acid-based management, although data identifying how such targets should be set are limited, the investigators said.
Finally, they said that despite the lack of data supporting the superiority of continuous renal replacement therapy, some clinicians may prefer to use it for patients with severe hemodynamic instability.
They pointed out that "the design and execution of research in this area has been hampered by a number of factors, including (1) lack of consensus with regard to the definition of acute renal failure and indications for dialysis, (2) limited understanding of the epidemiology of acute renal failure and (3) poorly designed and inadequately powered studies."
Most studies in this area were small and of poor quality, the researchers said. Given the paucity of good-quality evidence in this important area, additional larger randomized trials are needed to evaluate clinically important outcomes.
This study was supported by the Alberta Kidney Disease Network and the Canadian Agency for Drugs and Technology in Health.
Drs. Tonelli and co-author Braden Manns, M.D. were supported by New Investigator awards from the Canadian Institutes of Health Research. Dr. Tonelli was also supported by Population Health Investigator awards from the Alberta Heritage Foundation for Medical Research and by an alternative funding plan from the Government of Alberta, and the Universities of Alberta and Calgary.
Primary source: Journal of the American Medical Association
Source reference:
Pannu N, et al "Renal replacement therapy with acute renal failure: a systematic review"JAMA 2008; 299: 793-805.
http://www.medpagetoday.com/Nephrology/GeneralNephrology/tb/8418
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