1. Compared to patients treated with “on-pump” coronary artery bypass grafting, patients treated with “off-pump” surgery demonstrated a decreased rate of acute kidney injury.
2. However, no difference in loss of kidney function was noted between “on-pump” and “off-pump” techniques at 1-year post surgery.
Evidence Rating Level: 1 (Excellent)
Study Rundown: Coronary artery bypass graft (CABG) surgery is a mainstay of coronary revascularization. “On-pump” and “off-pump” surgeries differ not only in their techniques but also in their physiologic effects on the body. Cardiac surgery has proven association with kidney injury and failure. “On-pump” CABG involves a period of cardioplegia and routing of the blood supply through a cardiopulmonary bypass pump. “Off-pump” CABG is a newer technique where the heart continues to pump throughout the surgery without interruption. This study, a substudy of the Coronary Artery Bypass Grafting Surgery “Off”- or “On-pump” Revascularisation Study (CORONARY), sought to determine the effects of the two techniques on acute kidney injury (AKI) within 30 days and kidney function loss at 1-year post surgery. Using a randomized control trial study design with equal numbers of patients in both subgroups, this study demonstrated that acute kidney injury occurred at a higher rate in “on-pump” CABG patients, but found that kidney function loss was not different between the two groups at 1-year post surgery.
These results bring into question the practicality of immediate interventions to address AKI in not only the setting of CABG but also AKI from other etiologies. The study featured a large sample and robust randomization. While there is support for these findings, longer-term studies will be needed to fully elucidate the relationship between mild-moderate AKI and long-term kidney function in patients without multiple comorbidities predisposing them to an increased impact of AKI.
Relevant Reading: Acute kidney injury associated with cardiac surgery
In-Depth [randomized controlled trial]: This study, a substudy of CORONARY trial, sought to determine whether patients undergoing “on”- or “off-pump” CABG had varying rates of AKI and long term kidney function loss. AKI was defined as a greater than 50% increase in serum creatinine levels within 30 days post surgery, and kidney function loss was defined as more than 20% decrease in GFR. A total of 1472 patients were part of the “off-pump” cohort and 1460 patients were part of the “on-pump” cohort. Exclusion criteria included end-stage renal disease and lack of prerandomization creatinine levels along with criteria for the CORONARY trial. The “off-pump” group had a 0.83 (CI95, 0.72-0.97, p=.01) relative risk of developing AKI but did not have a significant difference in kidney function from the “on-pump” group at 1 year (17.1% versus 15.3%).
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