A new model for total cerebral ischemia in dogs

We have developed a new method producing total cerebral ischemia (TCI) in dogs; clamping ascending aorta with aorto-atrial bypass formation. Clamping ascending aorta provides TCI, the duration of which can be controlled up to the periods of 10 min. Beyond this interval, it is difficult to maintain TCI because of heart failure from high afterload. Blood outflow from left ventricle is completely obstructed except for coronary circulation which is small relative to the blood volume expelled from left ventricle, even if venous return to the heart is reduced. Aorto-atrial bypass formation during aortic clamping provides two distinctive advantages. First, adjusting aortic pressure in an appropriate level low enough not to overload myocardium but still high enough to maintain sufficient coronary blood flow is possible by regulating the blood flow through the bypass tubing, and secondly drug administration and blood volume control is possible through the tubing. These result in better preservation of myocardium, enabling longer TCI and longer survivals after TCI. We were successful in having up to 18 min of TCI with this method. Seventy-five percent of dogs of 12 min TCI and 40% of 15 min TCI survived 7 days, limit of experiment, after TCI, but no dogs of 18 min TCI survived for more than 3 days.