Bypass flow, mean arterial pressure, and cerebral perfusion during cardiopulmonary bypass in dogs.
OBJECTIVE
To determine if normal cardiopulmonary bypass (CPB) pump flows maintain cerebral perfusion in the context of reduced mean arterial pressure at 33 degrees C.


METHODS
A prospective investigation.


METHODS
Animal CPB research laboratory.


METHODS
Seven dogs that underwent CPB.


METHODS
Seven dogs underwent CPB at 33 degrees C using alpha-stat management and a halothane, fentanyl-midazolam anesthetic. Cerebral blood flow was measured using the sagittal sinus outflow technique. After control measurements at 70 mm Hg, cerebral physiologic values were determined under four conditions in random order: (1) mean arterial pressure of 60 mm Hg achieved by a reduction in pump flow, (2) mean arterial pressure of 60 mmHg determined by partial opening of a femoral arterial-to-venous reservoir shunt, (3) mean arterial pressure of 45 mm Hg by reduced pump flow, and (4) mean arterial pressure of 45 mm Hg by shunt. A 9F femoral arterial-to-venous reservoir shunt was controlled by a screw clamp.


RESULTS
Except for the controlled variables of mean arterial pressure and bypass flow, physiologic determinants of cerebral blood flow (temperature, PaCO2 and hematocrit) did not differ under any of the CPB conditions. Pump flow per se was not a determinant of cerebral perfusion. Cerebral blood flow and cerebral oxygen delivery did not differ with changes in pump flow if mean arterial pressure did not differ. Cerebral blood flow depended on mean arterial pressure under all pump flow conditions, however.


CONCLUSIONS
Over the range of flows typical in adult CPB at 33 degrees C, pump flow does not have an effect on cerebral perfusion independent of its effect on mean arterial pressure. A targeted pump flow per se is not sufficient to maintain cerebral perfusion if mean arterial blood pressure is reduced.
Sungurtekin
H
H
Department of Anesthesiology, Mayo Foundation and Mayo Clinic, Rochester, MN, USA.
Boston
U S
US
Cook
D J
DJ
D000818:Animals; D001783:Blood Flow Velocity; D001794:Blood Pressure; D001921:Brain / Q000378:metabolism; D002245:Carbon Dioxide / Q000097:blood; D002315:Cardiopulmonary Bypass / Q000379:methods; D002560:Cerebrovascular Circulation; D004285:Dogs; D006454:Hemoglobins / Q000032:analysis; D007427:Intracranial Pressure; D010101:Oxygen Consumption; D013696:Temperature
D006454:Hemoglobins; D002245:Carbon Dioxide