Fat reduction in pericardial suction blood by spontaneous density separation:: an experimental model on human liquid fat versus soya oil

Pericardial suction blood (PSB) contains mediastinal liquid wound fat with an embolic potential to cause brain damage after cardiopulmonary bypass (CPB). The aims were to measure how fat separates spontaneously from blood by density and how temperature and fat surface adhesion affect the results under experimental conditions. Human liquid fat was heat-extracted from retrieved pericardial fat tissue of coronary artery bypass graft (CABG) patients (n = 10). Human fat or soya oil, 5% and 10%, respectively, were mixed with postoperatively shed mediastinal blood (n = 20). The mixture was loaded into a temperature-controlled (37degreesC, 20degreesC, 10degreesC) vertical separation column. At 1, 2.5, 5 and 10 minutes, the blood was collected in five fractions, representing layers of density separation, followed by centrifugation. Human fat solidified at 8degreesC. Soya oil remained liquid below 0degreesC. Soya oil separated fast in water, but was slower in blood. At 10 minutes and 37degreesC 73+/-6% of added soya oil was found in the top 20% fraction. Human fat at 37degreesC behaved similarly to soya oil, with 58+/-2% separation at 10 minutes. However, at lower temperatures the density separation became less efficient (p <0.001), whereas human fat more effectively adhered to the walls of the column, which added to the removal. In total, 66%-78% of the human fat was removed, depending on temperature. In conclusion, fat in PSB can be reduced by simple density separation and surface adhesion while it is temporarily retained from the CPB circuit.