Temperature dependence of cerebral blood flow for isolated regions of the brain during selective cerebral perfusion in pigs.
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 degrees C and 30 degrees 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 (CMRO(2)) were assessed. Tissue samples from the cortex, cerebellum, hippocampus, and pons were taken for microsphere count.


RESULTS
The CBF and CMRO(2) decreased significantly (p < 0.002) during cooling in both groups; it was significantly higher throughout ASCP in the 30 degrees C versus the 25 degrees 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.
Department of Cardiothoracic Surgery, University Hospital of Cologne, Cologne, Germany. justus.strauch@uk-koeln.de
Justus T
JT
Strauch
Peter L
PL
Haldenwang
Katharina
K
Müllem
Miriam
M
Schmalz
Oliver
O
Liakopoulos
Hildegard
H
Christ
Jürgen H
JH
Fischer
Thorsten
T
Wahlers
D000818:Animals; D001013:Aorta, Thoracic / Q000601:surgery*; D001921:Brain / Q000098:blood supply*; D002560:Cerebrovascular Circulation; D005260:Female; D007036:Hypothermia, Induced; D007430:Intraoperative Care; D010477:Perfusion / Q000379:methods; D013552:Swine; D013696:Temperature; D014656:Vascular Surgical Procedures / Q000379:methods