Journal of Neuroimaging Vol 11 No 2 April 2001 Razumovsky et al: Cerebral Hemodynamics Changes Experimental Lab Investigations Cerebral Hemodynamics Changes During Retrograde Brain Perfusion in Dogs Alexander Y. Razumovsky, PhD Elaine E. Tseng, MD Daniel F. Hanley, MD William A. Baumgartner, MD ABSTRACT The objective of this study was to examine cerebral hemo- dynamics changes during hypothermic circulatory arrest (HCA) with and without retrograde cerebral perfusion (RCP). Thirteen colony-bred hound dogs were placed on cardiopulmonary bypass (CPB) and cooled to 18°C. Five dogs underwent 2 hours of HCA without RCP and 8 with RCP. The animals were then rewarmed on CPB until normothermic and weaned. Cerebral blood flow velocity (CBFV) and Gosling Pulsatility Index (PI) in the middle cerebral artery (MCA) were studied using trans- cranial Doppler ultrasound (TCD). At baseline and during pre- and postarrest CPB, there was anterograde direction of blood flow in the MCA. During HCA with RCP, there was retrograde direc- tion of blood flow in the MCA. There was no difference in CBFV between pre-, during, and postarrest CPB in the group with RCP; however, there was significantly increased CBFV during postarrest CPB in the group without RCP compared to the dogs with RCP. Later, at 3 hours after postarrest CPB, there was decreased CBFV in all animals accompanied by increased PI (2.4 ± 0.4 and 2.2 ± 0.6 for animals with RCP and without RCP, respectively) and abnormal TCD waveform changes including decreased diastolic compartment and sharp systolic peak. Dur- ing hypothermic circulatory arrest, RCP provides CBFV in the MCA comparable to MCA CBFV during CPB. HCA dogs without RCP showed immediate hyperemia on reperfusion. The decreased CBFV and increased PI at 1 hour after postarrest CPB could be an indicator of progressive ischemic injury due to the increased intracranial pressure despite the implementation of RCP. Key words: Transcranial ultrasound, cardiopulmonary bypass, blood flow velocity, cerebral perfusion. Razumovsky AY, Tseng EE, Hanley DF, Baumgartner WA. Cerebral hemodynamics changes during retrograde brain perfusion in dogs. J Neuroimaging 2001;11:171–178. Cardiopulmonary bypass (CPB), deep hypothermia, and hypothermic circulatory arrest (HCA) are well-established methods used to protect brain and cardiac function in patients with complex aortic aneurysms. Deep levels of hypothermia and HCA are known to reduce the neuronal injury associated with hypoxia. This protective mecha- nism is related to a decrease in metabolic rate in associa- tion with decreased temperatures and a simultaneous reduction in oxygen requirement by the neurons. How- ever, the sole use of HCA as a method for cerebral protections has its limits. As more complex cases were taken by vascular surgeons, there continued to be a need for new cerebral protective methods allowing for pro- longed, yet safe, cerebral preservation times. Ueda et al 1 introduced intermittent and later continuous retrograde cerebral perfusion (RCP) through the superior vena cava as an adjunct to HCA in an effort to extend the safe period of HCA in adults requiring aortic arch operations. RCP can provide blood flow and oxygen to the brain and may reduce ischemic damage. In addition, RCP can cool the brain homogeneously and maintain a low cerebral tem- perature. Despite widespread use of HCA with or without RCP for a variety of cardiac and complex aortic opera- Copyright © 2001 by the American Society of Neuroimaging 171 Received April 11, 2000, and in revised form July 20, 2000. Accepted for publication September 28, 2000. From the Department of Anesthesiology and Critical Care Medicine and the Department of Neurology (AYR), the Department of Surgery (EET, WAB), and the Depart- ment of Neurology (DFH), Johns Hopkins Medical Insti- tutions, Baltimore, MD. Address correspondence to Dr Razumovsky, Johns Hopkins Medical Institutions, Meyer 8-140, 600 North Wolfe Street, Baltimore, MD 21287-7840. E-mail: arazumov@jhmi.jhu.edu.