NORMOXIC CARDIOPULMONARY BYPASS REDUCES OXIDATIVE MYOCARDIAL DAMAGE AND NITRIC-OXIDE DURING CARDIAC OPERATIONS IN THE ADULT

Objective: Hyperoxic cardiopulmonary bypass is widely used during card iac operations in the adult. This management may cause oxygenation inj ury induced by oxygen-derived free radicals and nitric oxide. Oxidativ e damage may be significantly limited by maintaining a more physiologi c oxygen tension strategy (normoxic cardiopulmonary bypass). Methods: During elective coronary artery bypass grafting, 40 consecutive patien ts underwent either hyperoxic (oxygen tension = 400 mm Hg) or normoxic (oxygen tension = 140 mm Hg) cardiopulmonary bypass. At the beginning and the end of bypass this study assessed polymorphonuclear leukocyte elastase, nitrate, creatine kinase, and lactic dehydrogenase, antioxi dant levels, and malondialdehyde in coronary sinus blood. Cardiac inde x was measured before and after cardiopulmonary bypass. Results: There was no difference between groups with regard to age, sex, severity of disease, ejection fraction, number of grafts, duration of cardiopulmo nary bypass, or ischemic time. Hyperoxic bypass resulted in higher lev els of polymorphonuclear leukocyte elastase (377 +/- 34 vs 171 +/- 32 ng/ml, p = 0.0001), creatine kinase 672 +/- 130 vs 293 +/- 21 U/L, p = 0.002), lactic dehydrogenase (553 +/- 48 vs 301 +/- 12 U/L, p = 0.003 ), antioxidants (1.97 +/- 0.10 vs 1.41 +/- 0.11 mmol/L, p = 0.01), mal ondialdehyde (1.36 +/- 0.1 mu mol/L, p = 0.005), and nitrate (19.3 +/- 2.9 vs 10.1 +/- 2.1 mu mol/L, p = 0.002), as well as reduction in lun g vital capacity (66% +/- 2% vs 81% +/- 1%, p = 0.01) and forced 1-sec ond expiratory volume (63% +/- 10% vs 93% +/- 4%, p = 0.005) compared with normoxic management. Cardiac index after cardiopulmonary bypass a t low filling pressure was similar between groups (3.1 +/- 0.2 vs 3.3 +/- 0.3 L/min per square meter), [Data are mean +/- standard error (an alysis of variance), with p values compared with an oxygen tension of 400 mm Hg.] Conclusions: Hyperoxic cardiopulmonary bypass during cardi ac operations in adults results in oxidative myocardial damage related to oxygen-derived free radicals and nitric oxide. These adverse effec ts can be markedly limited by reduced oxygen tension management. The c oncept of normoxic cardiopulmonary bypass may be applied to surgical a dvantage during cardiac operations.