Cardiac troponins and volatile anaesthetics in coronary artery bypass graft surgery: A systematic review, meta-analysis and trial sequential analysis

BACKGROUND: Reports from animal studies indicate that volatile anaesthetics protect the myocardium against the effects of acute ischaemia-reperfusion injury by reducing infarct size. This cardioprotective effect in the clinical setting of coronary artery bypass graft (CABG) surgery, where the heart is subjected to global ischaemia-reperfusion injury, remains controversial. OBJECTIVE: The objective was to demonstrate that clinical studies investigating the cardioprotective effect of volatile anaesthetics on cardiac troponins in CABG are no longer warranted. We also investigated the effect of volatile anaesthetics on cardiac enzymes in off-pump cardiac surgery. DESIGN: Systematic review of randomised clinical trials, meta-analyses and trial sequential analysis (TSA). DATA SOURCES: Trials between January 1985 and March 2015 were obtained from electronic databases (Medline, Excerpta Medica Database (EMBASE), Cochrane Controlled Trial Register, abstracts from major anaesthesiology and cardiology journals and reference lists of relevant randomised trials and review articles. ELIGIBILITY CRITERIA: Relevant randomised clinical trials were included. We investigated the effect of volatile anaesthetics in both off-pump and on-pump CABG surgery with respect to troponin release [peak postoperative cardiac troponin I (cTnI) and cardiac troponin T (cTnT), cTnI/cTnT] and performed two separate meta-analyses. TSA was used to overcome the weakness of a type-1 error associated with repeated meta-analyses. RESULTS: From 30 studies, 2578 patients were pooled for the meta-analysis. The outcome significantly favours the use of peroperative volatile over non-volatile anaesthetics during on-pump CABG surgery with regard to peak postoperative cTnI (0.995 mg l; standard mean difference, 95% confidence interval, -1.316 to -0.673; P < 0.001). Meta-analysis of 11 off-pump studies showed no difference in peak postoperative cTnI (0.385 mg l; standard mean difference, 95% confidence interval, -0.857 to 0.087; P = 0.11). TSA indicated that the required information size for on-pump surgery was 1072 patients, and for off-pump surgery it was 1442; this latter figure has not yet been reached. CONCLUSION: Studies investigating the cardioprotective effect of volatile anaesthetics on cardiac troponins in on-pump CABG surgery are no longer warranted. This is not yet the case for off-pump surgery