Background: Despite improvements of the heart-lung machine (HLM), oxidative stress and subsequent damage to the alveolar capillary membrane still occur after conventional on-pump coronary artery bypass graft (CCABG) surgery. In an attempt to further improve the conventional HLM, a mini-extracorporeal circuit (MECC) was introduced. This new concept is based on minimal volume shifts. The extent of alveolar injury that is associated with this new technique is unknown. The lung-specific biomarkers Clara-cell 16 (CC16) and KL-6 are applied in this study to quantify alveolar dysfunction in both techniques.
Methods: In a prospective observational setting, the concentrations of CC16 and KL-6 were measured during and after 10 consecutive CCABG operations and 10 consecutive coronary artery bypass graft (CABG) operations using MECC (MCABGs). These pneumoproteins were measured after the induction of anesthesia, before clamping of the ascending aorta, after unclamping of the aorta, on arrival to the ICU, and on the following days until discharge. Quantification of the differences of KL-6 and CC16 leakage through the alveolar membranes between the two techniques was realized by calculation of the Student t test. Perioperative and postoperative shunt fractions and clinical observations were monitored simultaneously. The potential value of pneumoproteins as biomarkers for quantification of alveolar permeability during CABG surgery was tested.
Results: Significantly reduced concentrations of CC16 were found early after MCABG as compared to CCABG surgery (p = 0.033). KL-6 showed no consistent pattern during both treatment modalities. Early after CCABG surgery, shunt fractions tended to show reduced oxygen transport over the alveolar membrane as compared to MCABG surgery.
Conclusion: CC16 appears to be a useful biomarker for alveolar permeability during CABG surgery. Injury of the alveolar capillary membrane appears significantly reduced during MCABG surgery. Consistently early postoperative alveolar shunt fractions showed an increased value in CCABG compared to MCABG surgery in the early postoperative phase. Further randomized studies need to confirm the value of CC16 as marker in monitoring alveolar capillary damage during coronary bypass grafting.