A prospective randomized study to evaluate the renoprotective action of beating heart coronary surgery in low risk patients.

OBJECTIVES: Cardiopulmonary bypass (CPB) is widely regarded as an important contributor to renal failure, a well recognized complication following coronary artery surgery (coronary artery bypass grafting (CABG)). Anecdotally off-pump coronary surgery (OPCAB) is considered renoprotective. We examine the extent of renal glomerular and tubular injury in low-risk patients undergoing either OPCAB or on-pump coronary artery bypass (ONCAB). METHODS: Forty low-risk patients with normal preoperative cardiac and renal functions awaiting elective CABG were prospectively randomized into those undergoing OPCAB (n=20) and ONCAB (n=20). Glomerular and tubular injury were measured respectively by urinary excretion of microalbumin and retinol binding protein (RBP) indexed to creatinine (Cr). Daily measurements were taken from admission to postoperative day 5. Fluid balance, serum Cr and blood urea were also monitored. RESULTS: No mortality or renal complication were observed. Both groups had similar demographic makeup, Parsonnet score, functional status and extent of coronary revascularization (2.1+/-1.0 vs. 2.5+/-0.7 grafts; P=0.08). Serum Cr and blood urea remained normal in both groups throughout the study. A significant and similar rise in urinary RBP:Cr occurred in both groups peaking on day 1 (3183+/-2534 vs. 4035+/-4079; P=0.43) before reapproximating baseline levels. These trends were also observed with urinary microalbumin:Cr (5.05+/-2.66 vs. 6.77+/-5.76; P=0.22). Group B patients had a significantly more negative fluid balance on postoperative day 2 (-183+/-1118 vs. 637+/-847 ml; P=0.03). CONCLUSIONS: Although renal complication or serum markers of kidney dysfunction were absent, sensitive indicators revealed significant and similar injury to renal tubules and glomeruli following either OPCAB or ONCAB. These results suggest that avoidance of CPB does not offer additional renoprotection to patients at low risk of perioperative renal insult during CABG.