Is cardiopulmonary bypass responsible for systemic infalammation and cardiovascular dysfunction after cardiac surgery?

Aims: Numerous studies suggested that cardiopulmonary bypass (CPB) induces a systemic inflammatory response and subsequent myocardial and vascular dysfunction. However, it remains unclear how far CPB itself or subsequent cardioplegic arrest (CA) and reperfusion are responsible for these changes.

Methods: Three groups of dogs (n=12/each) were studied: group 1 underwent 90 minutes CPB with 60 minutes of crystalloid CA, group 2 underwent 90 minutes CPB without CA and group 3 served as control without CPB. The slope (Ees) of the end-systolic pressure-volume relationship was determined before and 60 minutes after CPB. Relaxation response of the coronaries isolated at the end of the experiments was examined. Plasma myeloperoxydase and malonaldehyde as indices of neutrophil activation and free radical generation were measured.

Results: While Ees decreased significantly in group 1 (58±8% of baseline, p<0.05) it remained unchanged in group 2 and 3 (96±8% and 101±11%). Response to acethylcholne was attenuated in group 1 in comparison to group 2 and 3 (70±7% vs. 86±2% vs. 83±4%, p<0.05). Both myeloperoxydase and malonaldehyde showed an approximately 3-fold increase in group 1 and 2 during CPB which however did not reach the level of significance. In group 1 a further doubling of myeloperoxidase and malonadehyde could be observed (p<0.05), while the values resolved at baseline level in group 2.

Conclusions: CPB alone leads to a transient and spontaneously reversible inflammatory response which however does not impair myocardial and vascular function. Concomitant CA and reperfusion are mainly responsible for declined cardiovascular function and prolonged systemic inflammation.