Off-pump versus on-pump coronary artery bypass grafting: oxidative stress and renal function

Oxidative stress and renal dysfunction occur in patients undergoing coronary artery bypass grafting with cardiopulmonary bypass (on-pump CABG). Whether the same adverse effects also occur during off-pump CABG is the question in this study.

Forty patients, 27 men and 13 women, undergoing elective CABG were included; 20 patients underwent on-pump CABG and 20 patients underwent off-pump CABG. Renal and ischemia/reperfusion injury parameters were studied, as well as malondialdehyde as a parameter for oxidative stress.

The renal function measured as the mean urinary creatinine excretion decreased significantly during surgery for the on-pump CABG group from 7.62+/-4.74 before surgery to 3.07+/-1.49 mmol/l after surgery, whereas no changes occurred in the off-pump CABG group. The mean urinary concentrations of hypoxanthine, xanthine and malondialdehyde expressed as creatinine ratios for the on-pump group increased significantly from 1.92+/-1.36, 6.06+/-3.62 and 0.21+/-0.07 before surgery to 11.88+/-5.77, 13.11+/-6.61 and 0.57+/-0.31 mmol/mol creatinine, respectively at arrival to the intensive care unit (ICU). During the next time-points, the purines and malondialdehyde decreased to 9.21+/-7.46, 7.55+/-3.95 and 0.32+/-0.13 mmol/mol creatinine, respectively after a 20 h stay at the ICU. For the off-pump CABG group, the mean ratios also increased significantly from 1.71+/-1.38, 2.01+/-0.96 and 0.16+/-0.10 before surgery to 4.73+/-3.19, 5.15+/-3.74 and 0.23+/-0.17 mmol/mol creatinine, respectively at arrival to the ICU. During the next time-points, the ratios of xanthine and malondialdehyde decreased to 3.80+/-2.92 and 0.24+/-0.13 mmol/mol creatinine, respectively. The ratio for hypoxanthine reached the highest ratio (6.97+/-5.67 mmol/mol creatinine) after a 9 h stay at the ICU, after which the ratio decreased to 5.98+/-5.56 mmol/mol creatinine after a 20 h stay at the ICU. However, all ratios from the on- and off-pump CABG patients still remained elevated compared with preoperative ratios. In addition, all ratios for the on-pump CABG group were elevated significantly at all time-points for xanthine, at time-points T2 and T4 for hypoxanthine and at time-point T2 for malondialdehyde as compared with the off-pump CABG group.

Only mild signs of oxidative stress and no renal dysfunction were found during and after off-pump CABG compared with on-pump CABG.