Longer duration of cardiopulmonary bypass is associated with greater numbers of cerebral microemboli

Background and Purpose-Many patients who undergo cardiac surgery assisted w ith cardiopulmonary bypass (CPB) experience cerebral injury, and microembol i are thought to play a role. Because an increased duration of CPB is assoc iated with an increased risk of subsequent cerebral dysfunction, we investi gated whether cerebral microemboli were also-more numerous with a longer du ration of CPB, Methods-Brain specimens were obtained from 36 patients who died within 3 we eks after CPB. Specimens were embedded in celloidin, sectioned 100 mu m thi ck, and stained for endogenous alkaline phosphatase, which outlines arterio les and capillaries. In such preparations, emboli can be seen as swellings in the vessels. Cerebral microemboli were counted in equal areas and scored as small, medium, or large to estimate the embolic load (volume of emboli) , Results-With increasing survival time after CPB, the embolic load declined (P<0.0001). (Lipid emboli are known to pump slowly through the brain.) Also with increasing time after CPB, the percentage of large and medium emboli became lower (P=0.0034). This decline is consistent with the concept-that t he emboli break into smaller globules as they pass through the capillary ne twork. A longer duration of CPB was associated with increased embolic load (P=0.0026). For each 1-hour increase in the duration of CPB, the embolic lo ad increased by 90.5%. Conclusions-Thousands of microemboli were found in the brains of patients s oon after CPB, and an increasing duration of CPB was associated with an inc reasing embolic load.