Chronic kidney disease as a risk factor for bleeding complications after coronary artery bypass surgery

Abstract

Background: The aim of the study is to define the role of chronic kidney disease (CKD) as a risk factor for postoperative bleeding in patients undergoing coronary artery bypass graft (CABG) surgery.

Methods: This is a retrospective cohort study of 238 consecutive patients who underwent isolated CABG surgery. Patients were followed up for the event of a significant bleed, defined as administration of either three or greater units of packed red blood cells, three or greater units of platelets, three or greater units of fresh frozen plasma, or any cryoprecipitate within 72 hours after a CABG procedure or undergoing a surgical revision for bleeding. Glomerular filtration rate (GFR) at baseline was calculated using the Cockroft-Gault formula. A final multiple logistic regression model was selected from a large set of presurgical and intraoperative covariates by using backward elimination (P > 0.20).

Results: After controlling for age, sex, elective versus emergent surgery, intraoperative activated clotting time, serum albumin level, extracorporeal bypass time, and baseline hematocrit, we found that even mild levels of renal impairment were associated with increased risk for postoperative bleeding: patients with a GFR of 40 mL/min or less had six times the odds of postoperative bleeding than patients with a GFR greater than 100 mL/min (odds ratio [OR], 6.51; 95% confidence interval [CI], 1.87 to 22.66); those with a GFR of 41 to 60 mL/min had nearly four times the risk (OR, 3.87; 95% CI, 1.21 to 12.35). Even patients with mild CKD at a GFR of 61 to 80 mL/min were at an elevated risk (OR, 2.11); however, the 95% CI of 0.79 to 5.64 included the null value. Similar results were found when using the cruder Kidney Disease Outcomes Quality Initiative classification of CKD.

Conclusion: CKD is associated with risk for postoperative bleeding in patients undergoing CABG surgery, not only at more advanced stages, but probably at relatively mild levels of renal impairment, as well.