Original article
Association Between Postoperative Acute Kidney Injury and Duration of Cardiopulmonary Bypass: A Meta-Analysis

https://doi.org/10.1053/j.jvca.2011.07.007Get rights and content

Objective

This meta-analysis examined the association between cardiopulmonary bypass (CPB) time and acute kidney injury (AKI).

Design

Meta-analysis of previously published studies.

Setting

Each single-center study was conducted in a surgical intensive care unit and/or academic or university hospital.

Participants

Adult patients undergoing heart surgery with CPB.

Interventions

A systematic literature review was conducted using PubMed, EMBASE, and Cochrane Library databases and Google Scholar from January 1980 through September 2009. Initial search results were refined to include human subjects, age >18 years, randomized controlled trials, and prospective and retrospective cohort studies, meet the Acute Kidney Injury Network definition of renal failure, and report times on CPB.

Measurements and main results

The length of time on CPB has been implicated as an independent risk factor for development of AKI after CPB (AKI-CPB). The 9 independent studies included in the final meta-analysis had 12,466 patients who underwent CPB. Out of these, 756 patients (6.06%) developed AKI-CPB. In 7 of the 9 studies, the mean CPB times were statistically longer in the AKI-CPB cohort compared with the control group (cohort without AKI). The absolute mean differences in CPB time between the 2 groups were 25.65 minutes with the fixed-effects model and 23.18 minutes with the random-effects model.

Conclusions

Longer CPB times are associated with a higher risk of developing AKI-CPB, which, in turn, has a significant effect on overall mortality as reported by the individual studies.

Section snippets

Defining Acute Kidney Injury

The primary outcome was the development of new-onset AKI-CPB as defined by the Acute Kidney Injury Network (AKIN) criteria.5 Before the use of the AKIN classification, there had been up to 37 different definitions of renal failure in the medical literature, which made these studies very heterogenous and difficult to compare. These definitions varied from a 25% increase over baseline creatinine to the need for dialysis.6 The need for a consensus definition that also could be used to validate

CPB Time as Risk Factor for AKI

The CPB times for subjects with AKI-CPB and controls in all 9 studies are reported in minutes (mean ± standard deviation) (Table 2). The overall and absolute mean differences of duration of CPB and 95% CIs for each study are reported in Fig 2. In all 9 studies, the patient cohort with AKI reported longer CPB times compared with the cohort that did not develop AKI-CPB (control).

The absolute mean differences between the cohorts (AKI-CPB and control) for individual studies ranged from 3 minutes

Discussion

The spectrum of CPB-induced pathophysiologic changes includes the systemic inflammatory response, changes in renal vasomotor tone, destruction of red cells, pigment nephropathy, loss of pulsatile flow, activation of complement and coagulation pathways, and generation of microemboli (fibrin, platelet aggregates, cellular debris, fat, and air).

Other established patient and surgical risk factors include advanced age, preoperative renal insufficiency, ejection fraction <40%, excessive hemodilution

Conclusions

Longer duration of CPB is associated with an increased risk of developing postoperative AKI.

Acknowledgments

The authors thank Drs Provonchère, Landoni, and Conlon for their willingness to discuss the project and provide specific anonymous data (Drs Landoni and Provonchère) from their previously published studies.

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