β-blockers and volatile anesthetics may attenuate cardioprotection by remote preconditioning in adult cardiac surgery: a meta-analysis of 15 randomized trials.

OBJECTIVE: Clinical trials on cardioprotection by remote ischemic preconditioning (RIPC) for adult patients undergoing cardiac surgery revealed mixed results. Previous meta-analyses have been conducted and found marked heterogeneity among studies. The aim of this meta-analysis was to evaluate the factors affecting cardioprotection by remote preconditioning in adult cardiac surgery.
DESIGN: A meta-analysis of randomized controlled trials.
SETTING: University hospitals. PARTICIPANTS: Adult subjects undergoing cardiac surgery.
INTERVENTIONS: RIPC.
MEASUREMENTS AND MAIN RESULTS: Fifteen trials with a total of 1,155 study patients reporting postoperative myocardial biomarker (CK-MB or troponin) levels were identified from PubMed, Embase, and the Cochrane Library (up to July 2012). Compared with controls, RIPC significantly reduced postoperative biomarkers of myocardial injury (standardized mean difference = -0.31, p = 0.041; heterogeneity test: I(2) = 83.5%). This effect seemed more significant in valve surgery (standardized mean difference = -0.74, p = 0.002) than in coronary artery surgery (standardized mean difference = -0.23; p = 0.17). Univariate meta-regression analyses suggested that the major sources of significant heterogeneity were β-blockers (%) (coefficient = 0.0161, p = 0.022, adjusted R(2) = 0.37) and volatile anesthetics (coefficient = 0.6617, p = 0.065, adjusted R(2) = 0.22). These results were further confirmed in multivariate regression and subgroup analyses.
CONCLUSIONS: Available data from this meta-analysis further confirmed the cardioprotection conferred by RIPC in adult cardiac surgery. Moreover, the cardioprotective effect may be attenuated when combined with β-blockers or volatile anesthetics.