CRD summary

This review concluded that initial renal replacement therapy modality in critically ill patients with acute kidney injury did not appear to affect mortality or recovery to renal replacement therapy independence. However, all the included studies showed methodological limitations and the authors' cautious conclusions that no meaningful inferences could be drawn from the evidence of this review appear to be justifiable.

Authors' objectives

To assess the effect of initial renal replacement therapy modality on clinical outcomes for critically ill patients with acute kidney injury.

Searching

MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) were searched from inception to December 2006 with no language restrictions. Search terms were reported. Reference lists of retrieved papers were reviewed. Manufacturers of commercially available renal replacement therapy and experts were contacted for unpublished studies. Conference abstracts and trials registers were searched.

Study selection

Randomised controlled trials (RCTs) of adult patients in intensive care units with acute kidney injury were eligible for inclusion if they compared continuous renal replacement therapy versus intermittent renal replacement therapy and reported mortality and renal recovery.

Most studies enrolled patients who were admitted to mixed medical/surgical intensive care units. Two trials enrolled participants with chronic kidney disease; most trials did not provide such information and so the overall percentage of chronic kidney disease was unknown. Most patients were male (61% to 87%). Where reported, mean age ranged from 53 to 76 years. Severity of illness was scored with different scales. Dose and duration and frequency of renal replacement therapy varied; no trial standardised and delivered an equivalent dose of dialysis between continuous and intermittent renal replacement therapies. Where reported, 60% to 100% of patients were on mechanical ventilation, 53.8% to 100% were on vasoactives and 41% to 100% had sepsis.

Two reviewers independently applied inclusion criteria and selected studies. Disagreements were resolved by discussion.

Assessment of study quality

Appropriate criteria were used to assess the quality of the included trials. Quality items included power calculation, randomisation, allocation concealment, blinding, description of losses to follow-up or missing outcome assessments, use of standardised protocols, evidence of baseline differences, predefined outcomes, treatment crossover, intention-to-treat analysis and funding source.

Two reviewers independently assessed study quality; how any disagreements were resolved was not reported.

Data extraction

Rates of mortality, renal recovery and renal death (defined as a composite of either death or non-recovery with dependence on renal replacement therapy) were extracted to calculate odds ratios (OR) with 95% confidence intervals (CI). Duration of renal replacement therapy, length of hospitalisation and cost were extracted to calculate mean differences with 95% CI. Some authors were contacted for clarification or missing data.

Two reviewers independently extracted data; how any disagreements were resolved was not reported.

Methods of synthesis

Pooled odds ratios with 95% CIs were calculated using a random-effects model. Pooled weighted mean differences (WMD) and 95% CI were calculated (method was not reported). Heterogeneity between trials was assessed by Χ² and I² statistics. Publication bias was assessed by Egger’s test and a funnel plot. Meta-regression and sensitivity analyses were performed to assess the impact of study quality and clinical factors on treatment effects.

Results of the review

Nine RCTs (n=1,403 patients; range 30 to 359) met the inclusion criteria. Seven trials reported the method of randomisation. Four trials reported adequate allocation concealment. None of the trials reported blinding or standardised criteria for initiation of renal replacement therapy. Four trials reported imbalances between groups at baseline. Four trials used an intention-to-treat analysis; treatment crossover occurred in fewer than 5% to 37.5% of trial participants.

There was no significant difference between continuous renal replacement therapy and intermittent renal replacement therapy in terms of mortality, recovery to renal replacement therapy independence and renal death. For treatment-related complications, continuous renal replacement therapy was associated with significantly fewer episodes of haemodynamic instability (OR 0.66, 95% CI 0.45 to 0.96, I²=47%), but not arrhythmic complications or bleeding episodes. These findings did not change in any of the sensitivity analyses. There was no evidence of publication bias from the Egger’s test or funnel plots.

For the assessment of heterogeneity, only the results for the I² test were presented.

Cost information

Costs were reported in one trial. Although direct costs per renal replacement therapy session were higher for continuous renal replacement therapy, there was no significant difference for per-patient treatment.

Authors' conclusions

Renal replacement therapy modality did not appear to affect mortality or recovery to renal replacement therapy independence. However, there were numerous issues of study design, conduct and quality identified that not only dispute the validity but also question any inferences that could be drawn from these trials.

CRD commentary

This review addressed a well-defined question in terms of participants, interventions, outcomes and study design. The search included appropriate electronic databases. There was no apparent indication of publication bias. To minimise bias and errors during the review process, two reviewers independently selected trials, extracted data and assessed the quality of the included trials. Characteristics of the individual trials were presented, but much of the study and population information was missing. Quality was assessed and the results for each criterion for each study reported, although some items not considered to be quality indicators were included in the assessment. Two studies were restricted to participants with continuous renal replacement therapy and most studies did not report whether patients with continuous renal replacement therapy were recruited; it was unclear how this would affect the generalisability of the results to patients with acute kidney injury in clinical practice. Potential sources of heterogeneity were explored. There seemed to be little or no statistical heterogeneity in most of the analyses, but clinical heterogeneity was apparent from the tables. Sensitivity analysis demonstrated that the results were robust to changes in the factors considered.

Given that all the included studies showed methodological limitations, the authors' cautious conclusions that no meaningful inferences could be drawn from the evidence of this review appear to be justifiable.

Implications of the review for practice and research

Practice: The authors did not state any implications for practice.

Research: The authors stated that high-quality and adequately powered trials were needed to address issues identified in the review.

Funding

Alberta Heritage Foundation for Medical Research; Canadian Institute for Health Research.

Bibliographic details

Bagshaw SM, Berthiaume LR, Delaney A, Bellomo R. Continuous versus intermittent renal replacement therapy for critically ill patients with acute kidney injury: a meta-analysis. Critical Care Medicine 2008; 36(2): 610-617. [PubMed: 18216610]

Original Paper URL

http://journals.lww.com/ccmjournal/Abstract/2008/02000/Continuous_versus_intermittent_renal_replacement.34.aspx

Indexing Status

Subject indexing assigned by NLM

MeSH

Acute Kidney Injury /mortality /therapy; Adult; Critical Illness; Hemofiltration /methods; Humans; Recovery of Function; Renal Dialysis /methods; Treatment Outcome

AccessionNumber

12008009303

Database entry date

16/02/2011

Record Status

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.