<qa>  What is the most common complications in patients undergoing cardiac surgery?Bleeding under cardiopulmonary bypass CPB is one of the most common complications in patients undergoing pediatric cardiac surgery. The inflammatory response produced during and after CPB is a factor that adds significantly to the morbidity after cardiac surgery. A number of factors have been shown to be involved inducing the inflammatory response. These include complement system activation3 and activation of inflammatory cytokines, especially IL-1 IL-64, IL-8 and TNF alpha. 