Emboli and Neuropsychological Outcome Following Cardiopulmonary Bypass

The dramatic decline in mortality related to cardiac surgery has resulted in over 330,000 surgeries involving cardiopulmonary bypass (CPB) being performed yearly in the United States. Although few patients die as a result of cardiac surgery, over two thirds of the patients demonstrate evidence of acute neuropsychological dysfunction postoperatively. The potential mechanisms contributing to post-CPB neuropsychological deficits are many, but two major inter-related etiologic factors, hypoperfusion and emboli, are suggested as the probable culprits. If embolism is the cause of the deficits, increasing cerebral perfusion would deliver more emboli and increase the amount and severity of injury. Conversely, if hypoperfusion is the cause of the injury, then decreasing brain blood flow to minimize embolic delivery would increase the likelihood of perfusion injury. By monitoring the carotid arteries of patients undergoing coronary artery bypass graft surgery, we have determined the frequency and quantity of embolic signals that occur during CPB. Although we have not been able to determine the nature of the embolus, gaseous or solid, we have demonstrated a relationship between the overall embolic load and the probability of having NP dysfunction.