Microemboli observed in deaths following cardiopulmonary bypass surgery: silicone antifoam agents and polyvinyl chloride tubing as sources of emboli

Abstract

Refractile foreign particles within clear vacuoles were observed in capillaries of 17 patients who underwent cardiopulmonary bypass surgery, died, and were autopsied at the George Washington University Hospital from December 1978 through April 1981. The postoperative survival time ranged from less than one day to more than eight months. The approximate maximal diameter of the individual particles was 10 micrometer and that of the vacuoles 60 micrometer. The particle-droplet complexes showed affinity for hydrophobic stains. In all 17 cases, the kidneys were involved in combination with several other organs. In two patients, the emboli were associated with microinfarcts in one or more organs. Scanning electron microscopy (SEM) of the polyvinyl chloride tubing used during four cardiopulmonary bypasses showed spallation and shredding of the luminal surface in the areas exposed to the roller pump heads. This suggested that fragments of polyvinyl chloride might be the particles in the emboli. Another possible source was the antifoam agent used in the bubble oxygenator. Scanning electron microscopy x-ray microprobe analysis of the foreign material within capillaries of several organs showed it to be strongly positive for silicon but not for chlorine. Therefore, it was concluded that the microemboli were droplets of antifoam agent, the refractile particles corresponding to the particulate silica component and the vacuoles corresponding to the dimethylpolysiloxane liquid component. Since x-ray microprobe analysis of the microemboli did not reveal a strong chloride peak, there is as yet no evidence that polyvinyl chloride fragments were involved in the microembolism. The morphologic findings reported here indicate that antifoam microembolization continues to complicate cardiopulmonary bypass surgery and must, therefore, be considered a potential cause of postoperative morbidity. The consequence of the fragments of polyvinyl chloride tubing released into the circulation remains to be established.