To the Editor:
I was pleased to see our work cited in the recent Review Article, “Cardiac Output and Cerebral Blood Flow: The Integrated Regulation of Brain Perfusion in Adult Humans.”1,2 Nevertheless, some conclusions made by the authors may have been misleading. They state that during cardiopulmonary bypass, alpha-stat management of carbon dioxide resulted in cerebral blood flow correlated with arterial blood pressure, whereas pH-stat management resulted in cerebral blood flow correlated with pump flow. Yet, clinical and laboratory evidence indicates that this explanation may be deficient. When Rogers et al.3 directly addressed this issue in a study of cardiac patients randomly assigned to either alpha-stat or pH-stat management, both groups showed cerebral blood flow dependent on arterial blood pressure and not dependent on cardiopulmonary bypass flow rate. Furthermore, Hindman et al.4 demonstrated that in pH-stat–managed rabbits, during constant-flow cardiopulmonary bypass, increases in arterial blood pressure resulted in large increases in cerebral blood flow. Meng et al.2 also state that during cardiopulmonary bypass, organ perfusion is propelled by centrifugal pump. However, in several studies they cite, cardiopulmonary bypass was by roller pump.5–7
The author declares no competing interests.