This review evaluated dialysis in patients with acute renal failure and concluded that outcomes were similar with IHD or CRRT, but that further good quality evidence was needed. Despite several limitations with the included studies, this was a generally well-conducted piece of research. The authors' cautious conclusions were likely to be reliable.

To evaluate the provision of dialysis for patients with acute renal failure (ARF) to identify optimal management and key areas for future research.

MEDLINE, EMBASE, all EBM Reviews and several grey-literature sources (including clinical trial registries, health technology assessment agencies and manufacturer websites) were searched to October 2007 for publications in English. References of relevant and retrieved articles were searched. Manufacturers and authors were contacted for details of further studies. Details of the search strategy were available on request from the website.

Randomised controlled trials (RCTs) and prospective cohort studies with 10 or more participants in two or more treatment arms assessing renal replacement therapies (RRTs) in patients with ARF were eligible for inclusion. Eligible studies were required to report the following outcomes: mortality, length of hospital stay, chronic dialysis dependence, blood pressure and hypotension (filter failure and bleeding complications for anticoagulant comparison). Data collected prospectively for registries or quality assurance databases were classed as retrospective and excluded.

Included studies were of adults, mostly men, with a mean age ranging from 35 to 70 years. Some patients had systemic inflammatory response syndrome (SIRS), others had liver failure/dysfunction and some used vasopressor. Most studies were conducted in the USA or Europe in an intensive care unit (ICU). Most studies compared continuous renal replacement therapy (CRRT) with intermittent haemodialysis (IHD) or compared two different types of IHD. Treatment groups used various different techniques/devices, membrane material, buffers, anti-coagulants and dosing regimens.

Two reviewers independently selected studies for relevance. Disagreements were resolved through consensus with a third person.

Two reviewers assessed RCTs for validity using the Jadad criteria (score of 0 to 5), including assessment of allocation concealment. Prospective cohort studies were assessed using items from the Downs and Black checklist, including treatment group accrual, withdrawals/dropouts and adjustment for potential confounders. In addition, studies were assessed for funding sources and intention-to-treat (ITT) analysis. Discrepancies were resolved through consensus with a third person.

Relative risks (RRs) or mean difference for change from baseline, with their 95% confidence intervals (CIs), were calculated.

One reviewer extracted data on outcomes and a second reviewer assessed data extraction for accuracy.

RRs for dichotomous data (mortality and chronic dialysis dependence in survivors) were pooled using a random-effects model by treatment modality. Weighted mean differences were pooled for mean arterial pressure (MAP). Where change from baseline correlations were not reported, a correlation of 0.5 was used. Where statistically significant heterogeneity was detected, sensitivity analyses excluding outliers were undertaken. Data on length of stay were not pooled due to skewed distributions. Heterogeneity was assessed using the I² test. Publication bias was not assessed due to the small number of included trials.

Thirty RCTs and eight prospective cohort studies (n=6,086) were included in the review. Sample sizes ranged from 26 to 1,218 patients. Four RCTs had adequate allocation concealment. RCTs scored between 0 and 3 on the Jadad scale (six scored 3). Four prospective studies were adjusted for potential confounders. Where reported, between zero and 18 patients were lost to follow-up. Nineteen studies were funded privately and/or publicly.

The evidence on the optimal indications for, and timing of, renal replacement in patients with ARF was inconclusive.

CRRT versus IHD (nine RCTs, n= 989)
There were no significant differences between treatment arms at follow-up for all-cause mortality, or ICU and in-hospital mortality (seven RCTs). Similar patterns were reported by four prospective cohort studies. There were no significant differences between treatment arms for the use of chronic dialysis treatment in surviving patients (five RCTs). Results from prospective cohort studies were unreliable.

There was no significant change in MAP from baseline between treatment groups in three RCTs. A fourth RCT reported that MAP increased slightly in patients treated with CRRT; 0.4mm HG (95% CI: 7.2 greater to 8.0 smaller). However, there was evidence of significant heterogeneity when these four RCTs were pooled (I²=99%). Two RCTs reported no significant differences between treatment groups for risk of hypotension. One prospective cohort study indicated decreased risk in patients receiving CRRT; RR: 0.68 (95% CI: 0.52, 0.87).

Sensitivity analyses on techniques for IHD and CRRT (three studies) did not significantly alter the findings and did not show any significant differences

Results for comparison of sustained low-efficiency dialysis (SLED) with a continuous modality (continuous venovenous haemofiltration or haemodialysis), dialysis dose, use of anticoagulants, dialysis membrane and dialysate were also reported in the review; study numbers were generally low.

The evidence showed that patients with ARF reported similar clinical outcomes when treated with IHD or CRRT, but further good quality evidence was needed.

The review question and supporting inclusion criteria were clear. An adequate search of the literature was undertaken. Only articles in English were sought, so language bias may have been introduced. Publication bias was not assessed and potentially relevant papers may have been missed. Validity was assessed using reliable criteria, but the quality of the included studies was generally low. Attempts were made to reduce the potential for reviewer error and bias at each stage of the review. Appropriate methods were used to synthesise the data and assess for heterogeneity, although p values were not reported and CIs appeared wide for a number of comparisons. Most comparisons included only a small number of studies, individual study data were not presented and no data were reported for length of hospital stay. This was a generally well-conducted piece of research. The authors acknowledged certain limitations with the included studies. The authors' cautious conclusions were likely to be reliable.

Practice: the authors did not state any recommendations for practice.

Research: the authors stated that future research should include studies of greater quality and larger sample size, and should clearly define subgroups of patients with ARF prior to study commencement. Future studies should also address how to improve patient outcomes after hospital discharge and measure duration of hospitalisation and use of resources. The authors acknowledged that such trials were underway at the time of writing.

Funding support was received from the Alberta Kidney Disease Network and the Canadian Agency for Drugs and Technology. Various researchers received awards from the Canadian Institutes of Health Research, Alberta Heritage Foundation for Medical Research, the Kidney Foundation of Canada, the Government of Alberta and universities of Alberta and Calgary.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.