Coronary, getting to the heart of AKI

Big nephrology has been beating the drum that acute kidney injury leads to chronic kidney disease. Leave it to the cardiac surgeons to produce some data and ruin the party.

There is a tidy bit of retrospective and observational data that shows that acute kidney injury precedes chronic kidney disease and the party line has been that we need to prevent AKI in order to prevent future chronic kidney disease and the hazards of dialysis. (http://www.ncbi.nlm.nih.gov/pubmed/21903988 and http://www.ncbi.nlm.nih.gov/pubmed/19406959) The best way to prove this would be to do a randomized controlled trial that reduces the rate of AKI and then track those patients into the future and see if the reduced rate of AKI translates into future protection from CKD. The problem with this type of analysis is that we really don’t have an effective and proven way to avoid AKI.

At today’s late breaking trial section, however Dr. Garg came to the rescue with an analysis of on-pump versus off-pump CABG surgery. This was a world wide trial that recruited people from North America, South America, Europe, Asia and Australia. They randomized almost 3,000 patients. They defined AKI using RIFLE Stage Risk, i.e. 50% bump in creatinine. He showed a slide with 7 different definitions of AKI and in all 7 they demonstrated a signifiant reduction in AKI with off-pump CABG. Using their prospectively defined definition of AKI they found a 17% reduction in AKI with off-pump CABG (17.5% vs 20.8%, P=0.01).

That was an amazing finding but the real question was did reducing the AKI reduce CKD at a year. They defined new CKD as a 20% loss of renal function. 15.3% of on-pump patients crossed that 20% threshold, less than the 17.1% who had an off-pump procedure, P=NS. So successfully avoiding AKI by getting the CABG done off-pump did not result in any reduction in CKD.

Dr. Garg then re-analyzed his data as a case-control study, i.e. when looking at just the patients who developed AKI there was an increase risk of CKD at a year. This is consistent with the existing body of retrospective studies showing AKI predicts future CKD, but we according to CORONARY the AKI is not causative. This is an important study that trashes the current AKI dogma.

Post written by Dr. Joel Topf, eAJKD Advisory Board member.

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