RESUMO
BACKGROUND: Hyperoxemic cardiopulmonary bypass (CPB) has been recognized as a safe technique and is widely used in cardiac surgery. However, hyperoxemic CPB may produce higher toxic oxygen species and cause more severe oxidative stress and ischemia/reperfusion injury than normoxemic CPB. This study was undertaken to compare inflammatory responses and myocardial injury between normoxemic and hyperoxemic CPB and to examine the beneficial effect of normoxemic CPB. MATERIAL AND METHOD: Thirty adult patients scheduled for elective cardiac surgery were randomly divided into normoxic group (n=15), who received normoxemic CPB (about PaO2 120 mmHg), and hyperoxic group (n=15), who received hyperoxemic CPB (about PaO2 400 mmHg). Myeloperoxidase (MPO), malondialdehyde (MDA), adenosine monophosphate (AMP), and troponin-T (TnT) concentrations in coronary sinus blood were determined at pre- and post-CPB. Total leukocyte and neutrophil counts in arterial blood were measured at the before, during, and after CPB. Lactate concentration in mixed venous blood was analyzed during CPB, and cardiac index (CI) and pulmonary vascular resistance (PVR) were evaluated pre- and post-CPB. All of the parameters were compared between the groups. RESULT: Normoxic group at post-CPB had lower MDA (4.79+/-0.7 vs 5.86+/-0.65 micromol/L, p=0.04) and MPO levels (5.38+/-1.01 vs 8.73+/-0.90 ng/mL, p=0.02), decreased total leukocyte counts (10,484+/-836 vs 13,572+/-1167/mm3, p=0.04) and higher AMP concentrations(1.23+/-0.07 vs 1.00+/-0.04 nmol/L, p=0.05), as well as a reduction in PVR (90.37+/-16.36 vs 118.12+/-12.21 dyne/sec/cm5, p=0.04) compared to hyperoxic group. There were no significant differences between the two groups with regard to TnT, lactate concentrations, and CI. CONCLUSION: Normoxic CPB provides less myocardial and lung damage related to oxygen free radicals and low inflammatory responses compared to hyperoxic CPB at post-CPB. Therefore, these results suggest that normoxemic CPB is a safe and salutary technique that could be applied in all cardiac surgery.