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Original Articles: Adult Cardiac

Temperature Dependence of Cerebral Blood Flow for Isolated Regions of the Brain During Selective Cerebral Perfusion in Pigs

^a Department of Cardiothoracic Surgery, University Hospital of Cologne, Cologne, Germany
^b Department of Experimental Medicine, University Hospital of Cologne, Cologne, Germany
^c Department of Biomathematics, University Hospital of Cologne, Cologne, Germany

Accepted for publication July 10, 2009.

^_* Address correspondence to Dr Strauch, University Hospital of Cologne, Department of Cardiothoracic Surgery, Kerpener Strasse 62, Cologne, 50925, Germany (Email: justus.strauch{at}uk-koeln.de).

Background: Hypothermic circulatory arrest (HCA) and antegrade selective cerebral perfusion (ASCP) are utilized for cerebral protection during aortic surgery. However, no consensus exists regarding optimal ASCP-temperature showing a tendency toward higher values during the last years. This study investigates regional changes of cerebral blood flow (CBF) during ASCP at two temperatures.

Methods: In this blinded study, 20 pigs (35 to 37 kg) were randomized to two groups. Animals were cooled to 10 minutes of HCA followed by 60 minutes of ASCP. Afterward the animals were perfused at 25°C and 30°C according to the study group. Fluorescent microspheres were injected at seven time points during the experiment to calculate total and regional CBF. Hemodynamics, cerebrovascular resistance (CVR) and cerebral metabolic rate of oxygen (CMRO₂) were assessed. Tissue samples from the cortex, cerebellum, hippocampus, and pons were taken for microsphere count.

Results: The CBF and CMRO₂ decreased significantly (p < 0.002) during cooling in both groups; it was significantly higher throughout ASCP in the 30°C versus the 25°C group (p = 0.0001). These findings were similar among all brain regions, certainly at different levels. The CBF increased significantly (p = 0.002) during the early period of ASCP for analyzed regions and decreased significantly (p = 0.034) below baseline after 60 minutes of ASCP, reaching critical levels in the hippocampus and neocortex. The hippocampus turned out to have the lowest CBF, while the pons showed the highest CBF. Thirty minutes and more ASCP provides less CBF compared with baseline values at both temperatures.

Conclusions: Antegrade selective cerebral perfusion improves CBF in all regions of the brain for a limited time. Our study characterizes the brain specific hierarchy of blood flow during ASCP. These dynamics are highly relevant for clinical strategies of perfusion.

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Invited Commentary

Davide Pacini
Ann. Thorac. Surg. 2009 88: 1514. [Extract] [Full Text] [PDF]

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				D. Pacini Invited commentary. Ann. Thorac. Surg., November 1, 2009; 88(5): 1514 - 1514. [Full Text] [PDF]