Pulmonary function is significantly reduced in the acute phase after coronary artery bypass graft (CABG) surgery. Because pulmonary function partly depends on respiratory muscle strength, we studied whether reductions in pulmonary function are related to postoperative alterations in circulatory factors that affect muscle protein synthesis.
Methods: Slow vital capacity (SVC) was assessed in 22 subjects before and 9 ± 3 days after CABG surgery. Blood testosterone, cortisol, insulin-like growth factor-1 (IGF-1), growth hormone, sex-hormone binding globulin (SHBG), glucose, insulin, c-peptide, c-reactive protein (CRP) content, and free androgen index, cortisol/testosterone ratio, HOMA-IR index were assessed before surgery and during the first three days after surgery. Intubation, surgery time and cumulative chest tube drainage were measured. Correlations between changes in SVC and blood parameters after surgery or subject characteristics were studied. This was a prospective observational study.
Results: After CABG surgery SVC decreased by 37 ± 18% (P < 0.01). Free androgen index, blood SHBG, testosterone and IGF-1 content decreased, while HOMA-IR index, cortisol/testosterone ratio, blood growth hormone, insulin and CRP content increased (P < 0.0025) in the first three days after surgery. Decrease in SVC was independently (P < 0.05) related to higher preoperative SVC (SC β = 0.66), and greater increase in blood cortisol (SC β = 0.54) and CRP (SC β = 0.37) content after surgery.
Conclusions: Larger reductions in pulmonary function after CABG surgery are present in patients experiencing greater postoperative increases in blood CRP and cortisol levels. Decrements in pulmonary function after CABG surgery are, at least in part, thus related to alterations in circulatory factors that affect muscle protein synthesis.
Keywords: Coronary artery bypass grafting; c-reactive protein; cortisol; pulmonary function; slow vital capacity.