Differential distribution of lipid microemboli after cardiac surgery

Background. Lipid microemboli found in shed blood during cardiac surgery have been shown to block capillaries of the brain postoperatively. In this study, the distribution of lipid microemboli in different regions of the brain and other organs was examined. A novel porcine model using radioactive lipid particles was used. Methods. Ten animals (2 controls and 8 cases) were anesthetized and put on cardiopulmonary bypass. A shed-blood phantom was produced from arterial blood, saline, and tritium-labeled triolein. The phantom was infused into the cardiopulmonary bypass circuit. Tissue samples were taken postmortem from examined organs and prepared for scintillation counting. Levels of radioactivity were used as a measure of the uptake of lipid microemboli. Results. High levels of radioactivity were found in kidney and spleen (5 to 10 times higher than in the other organs investigated). In the brain, radioactivity was found in all regions examined. The gray matter of cerebrum showed the highest level of the regions examined. Conclusions. This study shows that embolization of lipids is not a phenomenon restricted to the brain, but affected all the organs examined. The high levels found in the kidneys, and the relatively high levels in the gray matter of the cerebrum further legitimize the debate on the impact lipid microemboli has on postoperative kidney and cognitive dysfunction.