[Changes of neutrophil functions after cardiopulmonary bypass: experiment with dogs].

Objective: To investigate if increase of adhesion function and capability to destroy and decrease of phagocytosis of neutrophils occur after cardiopulmonary bypass (CPB).

Methods: 12 mongrel dogs were randomly divided into two equal groups: CPB group, weaned from CPB after 100 min of CPB; and sham group standing for 100 min without CPB. All dogs were observed for another 4 hrs. Blood samples were collected from the femoral vein before heparinization and by the end of experiment to measure the white blood cell count and classification, and expression of CD11b and CD18. Tissue samples of the right and left lungs were collected before heparinization and by the end of experiment. The expression of CD11b/CD18 in neutrophils, myeloperoxidase (MPO) activities in lung tissue, and pulmonary function were determined to access the adhesion function of neutrophils and the injuries to tissues. The phagocytotic activities, the release of MPO and the generation of oxygen free radical induced by IL-8 were surveyed to access the immune function of neutrophils.

Results: The fluorescence level of CD11b of the neutrophils in the CPB group was (2675 +/- 479) and the fluorescence level of CD18 of the neutrophils was (1574 +/- 262), both significantly higher than those before heparinization and those of the sham group (all P < 0.05). Four hours after CPB, the MPO activity of lung tissue of the CPB group was (55.02 +/- 21.04 U/100 g wet tissue), significantly higher than those before heparinization and that of the sham group (both P < 0.05); the ratios of PaO2/FiO2 of the CPB group was (319 +/- 79), significantly lower than those before heparinization and that of the sham group (both P < 0.05). Transmission electron microscopic examination revealed tentacle protrusion on the neutrophil in the CPB group, while the neutrophils were intact in the sham group. Contrary to the increase of adhere function, the numbers of neutrophil with phagocytic function of the CPB group was 35% +/- 11%, significantly lower than that of the sham group (74% +/- 9%, P < 0.01) the number of bacteria phagocytized by neutrophils per ml blood of the CPB group was (1484 +/- 238 ), significantly lower than that of the sham group (3106 +/- 714). There were no differences in the accumulated points of MPO in neutrophils, release of MPO, and generation of oxygen free radical between these 2 groups.

Conclusion: CPB causes neutrophil function disorder, including increase of adhesion function and reduction of phagocytic function.