Background: Although cardiopulmonary bypass generates a major inflammatory reaction and endothelial dysfunction, it is unclear that its avoidance in the setting of OPCAB leads to a significant decrease in the inflammatory insult. Controversial data is reported in the literature. The aim of our study was to assess whether off pump coronary surgery triggers less oxidative stress than on pump surgery.
Methods: Plasmas were sampled from patients before (T0), just after (T1) and 24h after (T2) cardiac surgery (6 on-pump and 6 off-pump CABG). Rings of thoracic aortas isolated from male Wistar rats were incubated for 24 hours with these different plasmas (100µl + 4 ml medium) or saline (control). Thereafter, superoxide anion production was assessed by the lucigenin(5µM)-enhanced chemiluminescence technique and mean signal recorded for 40 minutes was expressed as percent of control ring.
Results: In rat aorta exposed to plasma from on pump CABG patients, chemiluminescence signal was enhanced by 361±63 % at T1 (P<0.05 vs T0, n=6) and by 447±61% at T2 (p<0.05 vs T0, n=6). In contrast, exposure to plasma from off pump CABG patients did not enhance the signal: 1±5% at T1 and 15±15% at T2 (NS vs T0, n=6). Interestingly, the increase of superoxide production induced by on pump plasma was blunted by co-incubation with pravastatin 10µmol/L. Incubation with plasma lipid fractions did not enhance the signal at any time in any group. Nevertheless, ultracentrifugation of on pump plasma markedly blunted the enhanced signal at T1 and T2, whereas incubation with the microparticles (isolated by ultracentrifugation) almost completely restored the signal 154±39% at T1 (p<0.05 vs 25±12% at T0, n=5) and 107±18% at T2 (p=0.06, n=5). The mechanism seems endothelium-dependent since the chemiluminescence signal was almost completely blunted in rings without endothelium. CRP and SAA plasma levels were enhanced only at T2 in both groups.
Conclusion: Off pump CABG seems to produce less oxidative stress than on pump CABG, although inflammatory responses seem similar. Moreover, on pump-induced oxidative stress, which seems related to circulating microparticles, can be blunted by pravastatin co-incubation and is endothelium-dependent.