Refinement of survival prediction in patients undergoing lower extremity bypass surgery: stratification by chronic kidney disease classification

OBJECTIVE: End-stage renal disease (ESRD) imparts a significant survival disadvantage to individuals undergoing lower extremity revascularization; however, the influence of lesser degrees of renal impairment remains unclear. This study examined the prognostic significance of the chronic kidney disease (CKD) classification on survival, limb salvage, and graft patency in patients undergoing lower extremity arterial reconstruction. METHODS: A prospective registry was evaluated for consecutive patients between January 31, 1995, and December 21, 2004, undergoing first-time, lower extremity vein bypass surgery. Glomerular filtration rate (GFR) was estimated with the Modification of Diet in Renal Disease equation using each patient's preoperative creatinine concentration. CKD categories were taken from current National Kidney Foundation Kidney Disease Outcomes Quality Initiative staging criteria. RESULTS: The cohort included 456 subjects, with a mean (+/- SD) age of 68.1 +/- 10.8 years. There were 274 men (60%) and 378 Caucasians (82.5%). Comorbidities included diabetes mellitus in 270 (59.0%), hypertension in 333 (72.7%), coronary artery disease in 242 (52.8%), and dyslipidemia in 203 (44.5%). The surgical indication was critical limb ischemia in 384 (83.8%). Among the variables examined, diabetes and critical ischemia as the indication for bypass were significantly skewed toward higher CKD classifications (P < .001). The 5-year survival rates by CKD class were, CKD 1 and 2, 57%; CKD 3, 46%; CKD 4, 23%; and CKD 5, 9.5%. On univariate analysis, age, coronary artery disease, diabetes mellitus, hypertension, critical ischemia, and CKD were significant predictors of mortality. After adjustment, however, only age (hazard ratio HR], 1.05, 95% confidence interval CI], 1.03 to 1.06) and CKD stages 4 (HR, 4.23; 95% CI, 2.04 to 8.75) and 5 (HR, 3.27; 95% CI, 1.96 to 5.45) retained significance. Subjects within the CKD 5 classification were more likely to have a major amputation (P = .018) compared with all other CKD classes. Notably, no relationship was detected between CKD category and graft patency. CONCLUSION: CKD staging adequately differentiates survival curves and risk for major amputation among patients with renal impairment who are undergoing lower extremity bypass surgery. This may help in clinical decision analysis as well as in the refinement of stratification in future clinical trial design where survival is an end point.