Laser microprobe mass spectrometric study of aluminum and silicon in brain emboli related to cardiac surgery

Recent investigations have shown numerous fatty microemboli, which we previously termed small capillary and arteriolar dilatations (SCADs), in brain microvessels of patients who died after cardiac surgery assisted by cardiopulmonary bypass (CPB). The hypothesis of this study was that extraneous trace elements such as aluminum (Al) and silicon (Si) might be contaminating the blood and causing the formation of SCADs or coating the SCADs already formed in the extracorporeal circulation during CPB. Small capillary and arteriolar dilatations were identified in thick celloidin sections of the brains of 8 patients who died after cardiac surgery supported with a membrane oxygenator, and of 2 dogs that underwent CPB with a bubble oxygenator. The sections were infiltrated with Spurr's embedding medium for electron microscopy. Resin sections 0.5 microm thick were placed on 100-mesh copper grids and analyzed with laser microprobe mass spectrometry. Brain sections without SCADs from 3 patients (controls) whose deaths were not related to cardiac surgery were processed similarly. In SCADs and nearby neuropil sites of the 8 patients who had cardiac surgery, both Al and Si values were higher than in the neuropil, including vessels of the 3 controls. Si values were also high in the 2 dogs, in which a bubble oxygenator was used. Our results indicate that contamination with Al and Si continues to occur during cardiac surgery assisted by CPB. Our data also suggest that switching to membrane oxygenators from bubble oxygenators for CPB may have reduced Si contamination of blood. Further refinements of CPB aimed at eliminating microemboli formation and Al and Si entry into the circulation are warranted.