Surfactant protein B and RAGE increases in the plasma during cardiopulmonary bypass: a pilot study

Surfactant derived protein B (SPB) and plasma receptor for advanced glycation end products (RAGE) have been proposed as markers of lung injury. The former is produced specifically by pneumocytes while RAGE production is present in several body tissues. Cardiopulmonary bypass (CPB) generates a transient lung injury. We measured SPB and RAGE in plasma before surgery and after CPB, as well as 24 h and 48 h later. We analysed plasma samples from 20 subjects scheduled for elective coronary artery bypass grafting. We performed a quantitative analysis of plasma levels of RAGE and SPB mature form (8 kDa) by ELISA and a semi-quantitative analysis of SPB immature form (~ 40 kDa) by Western blotting. Surgery procedures were uneventful. After CPB RAGE median (75th-25th interquartile difference) increased from 633 (539) pg·mL⁻¹ to 1,362 (557) pg·mL⁻¹ (p < 0.01), while mature SPB increased from 5,587 (3,089) ng·mL⁻¹ to 20,307 (19,873) ng·mL⁻¹ (p < 0.01). RAGE and mature SPB returned to normal values within 48 h. This behaviour was confirmed when RAGE and SPB were normalised for protein content. Parallel changes were observed for immature SPB. Plasma RAGE and SPBs are sensitive and rapid markers of lung distress.