Low degree of activation of circulating neutrophils determined by flow cytometry during cardiac surgery with cardiopulmonary bypass

Background: Enhanced expression of adhesion molecules LFA-1 (CD11a/CD18) an d Mac-1 (CD11b/CD18) following cardiac surgery with cardiopulmonary bypass (CPB) is held responsible for postoperative complications. Surface expressi on of these molecules, intracellular pH (pH(i)), and oxidative burst capaci ty was analyzed to test for neutrophil activation during pediatric cardiac surgery. Methods: Blood samples were drawn from 36 patients (age: 3-16 year s) 24 h preoperatively, after onset of anesthesia, after connection to CPB (CPB1, before and after passing CPB, n = 15), at reperfusion (CPB2), and up to 7 days postoperatively, Cells adhering to CPB filters were isolated (n = 11). Antigen expression, pH(i), and oxidative burst capacity on neutrophi ls was analyzed by flow cytometry. Results: During surgery, oxidative burst capacity was at low level with a mild increase only 1 day after surgery. p H(i) was decreased throughout the surgery, Surgery induced more than 36% de crease of LFA-1 and Mac-1 expression (P < 0.03). Up to postoperative day 7, no increase of antigen expression above baseline was found. Neutrophils is olated from filters of the CPB had increased LFA-1 and Mac-1 expression tal l P < 0.05). Integrin expression on neutrophils passing the CPB at CPB1 was decreased (P < 0.05). Conclusion: Reduced adhesion molecule expression on neutrophils may be due to selective filtration of highly adhesive cells. Th is, in combination with low-level oxidative burst capacity, induced by immu nosuppressive cytokines (e.g., interleukin-10), reduced the neutrophil acti vity. Our data indicate that increased activity of circulating neutrophils cannot exclusively be held responsible for postoperative complications afte r surgery with CPB, Cytometry (Comm. Clin, Cytometry) 46:41-49, 2001, (C) 2 001 Wiley-Liss, Inc.