Systemic Free Radical Activation is a Major Event Involved in Myocardial Oxidative Stress

BACKGROUND:
Cardiopulmonary bypass (CPB) can induce deleterious effects that
could be triggered in part by radical oxygen species; however, their
involvement in the course of surgery has been elusive. The aim of
this study was to evaluate the time course and origin of radical
oxygen species release, myocardial or not, in patients undergoing
coronary artery surgery involving CPB.

METHODS: Blood
samples were taken from periphery and coronary sinus of patients
during CPB, and oxidative stress was evaluated by direct and
indirect approaches. Direct detection of alkyl and alkoxyl radicals
was assessed by electron spin resonance spectroscopy associated with
the spin-trapping technique using alpha-phenyl-N-tert-butylnitrone.


RESULTS: The authors showed that the spin adduct
concentration was not influenced by anesthesia and pre-CPB surgery.
A rapid systemic increase of plasma spin adduct concentration
occurred after starting CPB, and it stayed at a high concentration
until the end of CPB. At the beginning of reperfusion period,
radical oxygen species release was accelerated in the coronary
sinus; however, it was not significant. A positive correlation was
found between alpha-phenyl-N-tert-butylnitrone adduct concentrations
and (1) the duration of CPB and (2) concentration of postoperative
creatine phosphokinase of muscle band (CPK MB). Plasma vitamin E and
C, ascorbyl radical, uric acid, thiol, plasma antioxidant status,
and thiobarbituric acid reacting substances were also measured but
did not give relevant indications, except for uric acid, which
seemed to be consumed by the heart during reperfusion.

CONCLUSION: The results indicate that a systemic
production of free radicals occurs during CPB that may overwhelm the
production related to reperfusion of the ischemic heart. This
systemic oxidative stress is likely to participate in secondary
myocardial damage.