Original Investigation
Pathogenesis and Treatment of Kidney Disease
Acute Kidney Injury and Prognosis After Cardiopulmonary Bypass: A Meta-analysis of Cohort Studies

https://doi.org/10.1053/j.ajkd.2014.09.008Get rights and content

Background

Robust estimates and sources of variation in risks of clinical outcomes for cardiopulmonary bypass (CPB)-associated acute kidney injury (AKI) are needed to inform clinical practice and policy. We aimed to assess whether the methods for defining acute kidney disease modify the estimated association of AKI with CPB.

Study Design

Systematic review and meta-analysis.

Setting & Population

Adults undergoing CPB.

Selection Criteria for Studies

Cohort studies reporting adjusted associations between CPB-associated AKI and early mortality, later mortality, stroke, myocardial infarction, congestive heart failure, all-cause hospitalization, chronic kidney disease, end-stage kidney disease, bleeding complications, or perioperative infection.

Predictors

CPB-associated AKI and renal replacement therapy.

Outcomes

The primary outcome was early mortality (in-hospital or within 90 days of surgery) in studies reporting adjusted associations and secondary outcomes including total and cardiovascular mortality, major adverse cardiovascular events, rehospitalization, end-stage kidney disease, bleeding, and perioperative infection.

Results

46 studies with 47 unique cohorts comprising 242,388 participants were included. The pooled rate of CPB-associated AKI was 18.2%, and of renal replacement therapy, 2.1%. CPB-associated AKI was associated with early mortality (risk ratio [RR], 4.0; 95% CI, 3.1-5.2; crude mortality with CPB-associated AKI, 4.6%; without CPB-AKI, 1.5%) with considerable heterogeneity between studies (I2 = 87%). The AKI definition did not modify prognostic estimates (P for subgroup analysis = 0.9). When heterogeneity was fully accounted for using credibility ceilings, risks of early mortality were attenuated (RR, 2.2; 95% CI, 1.8-2.8) but remained high. Renal replacement therapy also was associated with early mortality (RR, 5.3; 95% CI, 3.4-8.1). CPB-associated AKI also was associated with long-term mortality (RR, 2.0; 95% CI, 1.7-2.3) and stroke (RR, 2.2; 95% CI, 1.1-4.5). No other outcomes were reported in more than 3 studies.

Limitations

Unclear attrition from follow-up in most studies and variable adjustment for confounders across studies.

Conclusions

CPB-associated AKI is associated with a more than 2-fold increase in early mortality regardless of AKI definition.

Section snippets

Study Protocol

This systematic review and meta-analysis was conducted using a prespecified protocol and according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA).6

Search Strategy and Selection Criteria

We searched MEDLINE and EMBASE without language restriction for January 1, 2004, to June 2, 2014, using the following medical subject heading (MeSH) terms: acute kidney injury, renal failure, renal replacement therapy, dialysis, cardiac surgical procedure, cardiopulmonary bypass, coronary artery bypass, mortality,

Description of Included Studies and Participants

The systematic search identified 3,618 citations, of which 320 were retrieved for full-text examination after review by title and abstract. Overall, 46 studies reporting on 47 cohorts comprising 242,388 patients (Fig 1; Table 1) were eligible and included in the review. Sample size varied from 68 to 28,220 (median, 1,610) participants (Table 1). There were 45 cohorts adjusted for covariates reporting at least one of early or late mortality outcomes. Data were extractable for the association

Discussion

This meta-analysis including 242,000 patients at risk of AKI after CPB highlights the prognostic importance of AKI. Adults experiencing CPB-associated AKI experienced markedly increased premature mortality following surgery. Importantly, differing consortia- or guideline-based definitions for AKI provided similar prognostic information about CPB-associated AKI for early death in this clinical setting. Markedly increased risks of death with CPB-associated AKI persisted even when inconsistencies

Acknowledgements

We thank the multiple authors who responded to our requests for additional information.

Support: None.

Financial Disclosure: Dr Pickering has undertaken consultancy for AMPharma. The other authors declare that they have no relevant financial interests.

Contributions: Research idea and study design: JWP, SCP, MJ; data acquisition: JWP; data analysis/interpretation: JWP, SCP, MJ; statistical analysis: JWP. Each author contributed important intellectual content during manuscript drafting or revision

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