Published: May 17, 2012

Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston.

Action Points

For patients with impaired renal function, performing CABG off-pump rather than on-pump appears to improve outcomes, a retrospective study showed.

Across the range of renal function, off-pump CABG was associated with a slightly lower rate of in-hospital death or the need for renal replacement therapy compared with on-pump CABG (1.8% versus 2%), according to Lakhmir Chawla, MD, of George Washington University Medical Center, and colleagues.

The benefit of off-pump CABG increased as renal function worsened, the researchers reported online in the Journal of the American Society of Nephrology.

"Prospective trials comparing these procedures in patients with impaired preoperative renal function are warranted," they wrote.

Patients with prolonged exposure to cardiopulmonary bypass have been shown to have a greater risk of postoperative acute kidney injury, and off-pump CABG has been proposed for high-risk patients.

"The link between cardiopulmonary bypass and acute kidney injury is plausible, especially among patients with limited preoperative renal reserve," the researchers wrote, citing detrimental effects from low mean arterial pressures during bypass, the kidney's vulnerability to ischemia, and possible contributions from nonpulsatile renal perfusion, microemboli, and systemic inflammation.

"Despite this mechanistic association, prospective controlled trials of off-pump CABG have included few patients with chronic kidney disease," they wrote.

To compare outcomes from off-pump and on-pump CABG in patients with various levels of renal function, Chawla and colleagues examined data from 742,909 non-emergent CABG cases -- including 158,561 off-pump procedures -- from the Society of Thoracic Surgeons' Adult Cardiac Surgery Database from 2004 through 2009.

Nearly a quarter (24.1%) of the patients had chronic kidney disease -- defined as an estimated glomerular filtration rate less than 60 mL/min/1.73 m².

After adjustment for patient differences at baseline with propensity weighting, the rate of in-hospital death or the need for renal replacement therapy was lower in the off-pump CABG group, with rates highest in the patients with an eGFR of 15 to 29 mL/min/1.73 m² (12.4% off-pump versus 16% on-pump).

The absolute difference in risk of the composite outcome ranged from a nonsignificant 0.05 per 100 patients for the group with an eGFR of 90 mL/min/1.73 m² or higher to a significant 3.66 per 100 patients for the group with an eGFR of 15 to 29 mL/min/1.73 m².

A reduced need for renal replacement therapy among patients with poor renal function drove the differences.

An analysis further adjusting for potential bias introduced by patients crossing over from one group to the other and unmeasured confounding associated with treatment selection rendered most of the between-group differences nonsignificant, although off-pump CABG remained associated with significantly lower rate of the composite outcome in the patients with the worst renal function.

The authors acknowledged some limitations of the study, including the retrospective, nonrandomized design and the fact that off-pump CABG has a significant learning curve.

The authors reported that they had no conflicts of interest.

Primary source:Journal of the American Society of Nephrology
Source reference:
Chawla L, et al "Off-pump versus on-pump coronary artery bypass grafting outcomes stratified by preoperative renal function" J Am Soc Nephrol 2012; DOI: 10.1681/ASN.2012020122.

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Todd Neale

Senior Staff Writer

Todd Neale, MedPage Today Staff Writer, got his start in journalism at Audubon Magazine and made a stop in directory publishing before landing at MedPage Today. He received a B.S. in biology from the University of Massachusetts Amherst and an M.A. in journalism from the Science, Health, and Environmental Reporting program at New York University. He is based at MedPage Today headquarters in Little Falls, N.J.

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