Predictors of surgery-induced muscle proteolysis in patients undergoing cardiac surgery

Muscle proteolysis due to post-operative hypercatabolism is responsible for the functional decline observed in patients undergoing cardiac surgery. The aim of this study was to explore the factors underlying increased muscle proteolysis by measuring the urinary 3-methylhistidine/creatinine ratio (3-MH/Cr) in patients who had recently undergone cardiac surgery.

Sixty-nine patients undergoing elective cardiac surgery participated in this study. The 24-h urinary 3-MH/Cr was collected for 3 days after surgery. Serum levels of metabolic markers, amino acids, and skeletal muscle strength were measured before and after surgery. Cumulative 3-MH/Cr during 3 days after surgery (cum3-MH/Cr) was 676.7±169.0nmol/gCr, and was positively associated with the decrease in muscle strength. In multivariate analysis, factors associated with an increased cum3-MH/Cr were preoperative grip strength (β=-0.309, p=0.003), body mass index (β=-0.299, p=0.001), hemoglobin (β=-0.243, p=0.007), cardiopulmonary bypass time (β=0.184, p=0.049), and immediate post-operative interleukin-6 (β=0.295, p=0.002).

Our findings suggest that post-operative muscle proteolysis is facilitated by preoperative catabolic accelerators in patients undergoing cardiac surgery. The factors of muscle proteolysis immediately after surgery may be a novel therapeutic target in rehabilitation intervention.