It has been shown that white cells and platelets release their granules into the plasma of salvaged blood. Whether this release is due to destruction alone or a combination of destruction and activation is not known. Lipid mediators, platelet-activating factor and leukotriene B4, are produced by activated white cells and platelets and have effects on the cardiovascular, respiratory and immune systems and the microcirculation. The aim was to determine if white cells and platelets are activated in salvaged blood by measuring the levels of these lipid mediators. Ten patients undergoing aortic surgery, where intraoperative salvage was used, were studied. Blood samples were taken from the patient's circulation and the salvaged blood before and after washing. The levels of leukotriene (LTB4) and lyso platelet-activating factor (PAF, the stable degradation product of PAF) were measured in the samples by a radioimmunoassay and a bioassay, respectively. The levels of both these substances increased in the unwashed salvaged blood (mean patient levels: LTB4 27 +/- 4.3 ng/ml and L-PAF 73 +/- 8.5 ng/ml; mean unwashed blood levels: LTB4 95 +/- 12.2 ng/ml and L-PAF 172.9 +/- 26.4 ng/ml) and were reduced by washing of the collected blood (mean washed blood levels of LTB4, 23.9 +/- 4.8 ng/ml, and L-PAF 18 +/- 5 ng/ml). The increase of the lipid mediators in the unwashed salvaged blood indicates that white cells and platelets are activated and releasing lipid mediators. Washing of the collected blood is effective in removing the lipid mediators.