Pharmacological preconditioning with hyperbaric oxygen: can this therapy attenuate myocardial ischemic reperfusion injury and induce myocardial protection via nitric oxide?

Ischemic reperfusion injury (IRI) is an inevitable part cardiac surgery such as coronary artery bypass graft (CABG). While ischemic hypoxia and the ensuing normoxic or hyperoxic reperfusion are critical to the initiation and propagation of IRI, conditioning myocardial cells to an oxidative stress prior to IRI may limit the consequences of this injury. Hyperbaric oxygen (HBO2) is a modality of treatment that is known to generate an oxidative stress. Studies have shown that treatment with HBO2 postischemia and reperfusion is useful in ameliorating myocardial IRI. Moreover, preconditioning the myocardium with HBO2 before reperfusion has demonstrated a myocardial protective effect by limiting the infarct size post ischemia and reperfusion. Current evidence suggests that HBO2 preconditioning may partly attenuate IRI by stimulating the endogenous production of nitric oxide (NO). As NO has the capacity to reduce neutrophil sequestration, adhesion and associated injury, and improve vascular flow, HBO2 preconditioning induced NO may play a role in providing myocardial protection during interventions that involve an inevitable episode of IRI. This current opinion review article attempts to suggest that HBO2 may be used to pharmacologically precondition and protect the myocardium from the effects of IRI that is known to occur during cardiac surgery.