Cardiopulmonary bypass and pulmonary surfactant: influence on composition and function?

Objectives

To characterize early pulmonary surfactant features in children undergoing cardiovascular surgery with cardiopulmonary bypass (CPB).

Methods

Fifty children were undergoing cardiac surgery for congenital heart disease: 35 procedures with CPB and 15 without (control group). Tracheal aspirates (TA) were obtained by saline lavage before and after CPB, and 4, 8 and 24 hours after pediatric intensive care unit admission. Total protein and phospholipid (PL) contents were assessed in native TA, in functional active large surfactant aggregates (LA), and in degraded small aggregates (SA). PL profiles, surfactant apoproteins SP-A, SP-B and SP-C (enzyme-linked immunosorbent assay), and surface activity (bubble surfactometer) were analyzed in LA only.

Results

Surfactant properties did not change in the control group. In the CPB group, PL content increased in TA 24 hours after CPB. LA concentration dropped 4 hours after CPB (P < 0.01) but recovered within 24 hours. The PL : protein ratio of LA was decreased at 24 hours as compared with baseline (P < 0.01). The relative amount of phosphatidylglycerol in LA-PL content dropped linearly over time. The relative content of the hydrophobic SP-B and SP-C in LA increased almost threefold as compared with baseline. There were no significant changes in biophysical function of LA.

Conclusions

CPB in children induces profound changes in the surfactant system, involving both PL and protein components. Biophysical function may be maintained by compensatory increases in SP-B and SP-C of LA.