Graded reoxygenation limits lipid peroxidation during surgical reperfusion.

Background: Most cardiac operations with cardiopulmonary bypass (CPB) are conducted with high oxygen partial pressure. The hyperoxic reoxygenation of the ischemic heart induced by aortic declamping may be an important component of cardiac reperfusion injury. The present clinical study assessed the preventive effect of graded reoxygenation on lipid peroxidation. Malondialdehyde (MDA) levels reflect lipid peroxidation, and therefore can be used to quantify reoxygenation damage.

Material/methods: 19 patients with coronary artery disease were enrolled consecutively and divided into two groups. In Group I, graded reoxygenation was initiated 1 min before, and continued for 9 min after aortic declamping (paO2: 50-70 mmHg, n=10). Patients undergoing conventional hyperoxic reoxygenation (paO2: >250 mmHg) on CPB (Group II, n=9) served as controls. Blood was collected before commencement of CPB, 2 min before release of the aortic crossclamp, 1 min and 10 min after release of the aortic crossclamp, and 3 hours after CPB.

Results: MDA levels [KM/l] did not differ between groups before CPB, but 1 min after aortic declamping MDA increased significantly more in group II (11.02 +/- 1.05; p=0.04) as compared to group I (8.16 +/- 0.74). There was no difference between groups late after reperfusion.

Conclusions: Hyperoxic reoxygenation by release of the aortic crossclamp is associated with increased MDA levels immediately after aortic declamping. Graded normoxic reoxygenation therefore limits lipid peroxidation in the early reperfusion period.