BRAIN MICROEMBOLI ASSOCIATED WITH CARDIOPULMONARY BYPASS - A HISTOLOGIC AND MAGNETIC-RESONANCE-IMAGING STUDY

Emboli in brain tissue after cardiopulmonary bypass were reported in t he literature 30 years ago, but there is little objective evidence con firming the presence of emboli in the brain after cardiopulmonary bypa ss with more modem equipment and techniques. Recently, with alkaline p hosphatase vascular staining, we found an acellular fatty material in brain microvasculature from autopsy material of patients who died shor tly after cardiopulmonary bypass. These fatty intravascular collection s range in diameter from 10 to 70 mu m, a size that lodges in the smal lest vessels of the microvasculature. They have been found in numbers sufficient to cause detectable neurologic dysfunction and are believed , but not proved, to be emboli. By sequentially injecting colored micr ospheres, we can determine when emboli occur during experimental cardi opulmonary bypass. In ongoing related studies, magnetic resonance imag ing was performed before cardiac valve replacement in 39 patients for whom preoperative and postoperative neurologic and neuropsychologic te sting was available. Preliminary results suggest that magnetic resonan ce imaging evidence of prior stroke is not a significant risk factor f or cognitive or motor decrement after cardiopulmonary bypass.