Indices of oxidative stress in urine of patients undergoing coronary artery bypass grafting.

Indices of oxidative stress in urine were measured in twenty patients undergoing elective coronary artery bypass grafting. Hypoxanthine, xanthine and uric acid were measured in urine, as markers of ischaemia together with malondialdehyde, which is a marker for lipid peroxidation. To correct for renal dysfunction during coronary artery bypass grafting the creatinine concentration was measured in urine and plasma. The creatinine concentration in plasma increases significantly during surgery, from 84 +/- 23 mumol/l to 133 +/- 52 mumol/l, whereas the creatinine concentration in urine decreases significantly, from 8.29 +/- 4.45 mmol/l to 2.70 +/- 1.01 mmol/l, during reperfusion. For reasons of comparison, the values of the observed measurements in urine are expressed per mol creatinine. The hypoxanthine and xanthine excretions both increase significantly, from 15.0 +/- 7.3 and 10.9 +/- 5.7 mmol/mol creatinine, respectively, after induction of anaesthesia to a maximum of 33.1 +/- 16.7 and 17.4 +/- 11.1 mmol/mol creatinine, respectively, during reperfusion. The malondialdehyde excretion increases significantly, from 1.38 +/- 0.80 mmol/mol creatinine after induction of anaesthesia to a maximum of 3.87 +/- 1.87 mmol/mol creatinine during reperfusion. The purines and malondialdehyde in urine (expressed as a ratio of creatinine), increase during coronary artery bypass grafting as a consequence of oxygen mediated tissue injury.