In vivo measurement of circulating leucocyte activation in patients following cardiopulmonary bypass

We have developed a simple technique to measure in vivo activation of circulating leucocytes and assessed it in 6 patients undergoing cardiopulmonary bypass (CPB). Arterial, mixed venous, and jugular bulb blood samples were taken following i.v. [18F]FDG, before and after CPB. [18F]FDG uptake in leucocytes was measured by phosphor imaging of spun blood-filled capillary tubes. Leucocyte radioactivity was quantified ([(leucocytes-plasma)/plasma radioactivity] and normalised to leucocyte counts. [18F]FDG uptake (mean±SEM)) before CPB was undetectable, being -0.014±0.007, -0.011±0.003, -0.012±0.006, -0.010±0.005, whereas increased uptake was demonstrated following CPB, 0.006±0.006, 0.009±0.005, 0.021±0.005, 0.034±0.006, at 20, 40, 60, and 80 min, respectively. There was no significant difference in activation between sampling sites before or after CPB. This method gives a sensitive index of activation of circulating leucocytes in whole blood, enabling investigation of activation of circulating white cells without the influence of sample handling or the requirement for time-consuming cell separation procedures