Abstract
INTRODUCTION: Pyruvate dehydrogenase (PDH) is a key gatekeeper enzyme in aerobic metabolism. The main purpose of this study was to determine if PDH activity is affected by major stress in the form of coronary artery bypass grafting (CABG), which has previously been used as a model of critical illness. METHODS: We conducted a prospective, observational study of patients undergoing CABG at an urban, tertiary care hospital. We included adult patients undergoing CABG with or without concomitant valve surgery. Measurements of PDH activity and quantity and thiamine were obtained prior to surgery, at the completion of surgery, and 6 h after surgery. RESULTS: Fourteen patients were enrolled (aged 67 ± 10 years, 21% female). Study subjects had a mean 41.7% (SD, 27.7%) reduction in PDH activity after surgery and a mean 32.0% (SD, 31.4%) reduction 6h after surgery (P < 0.001). Eight patients were thiamine deficient (≤ 7 nmol/L) after surgery compared with none prior to surgery (P = 0.002). Thiamine level was significantly associated with PDH quantity at all time points (P = 0.01). Postsurgery lactate levels were inversely correlated with postsurgery thiamine levels (r = -0.58 and P = 0.04). CONCLUSION: The stress of major surgery causes decreased PDH activity and quantity and depletion of thiamine levels.