β-Blockers and Reduction of Cardiac Events in Noncardiac Surgery

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Abstract
Context Recent studies suggest that perioperatively administered β-blockers may reduce the risk of adverse cardiac events in patients undergoing major noncardiac surgery. Objective To review the efficacy of perioperative β-blockade in reducing myocardial ischemia, myocardial infarction, and cardiac or all-cause mortality from randomized trials. Data Sources A MEDLINE and conventional search of English-language articles published since 1980 was performed to gather information related to perioperative cardiac complications and β-blockade. Reference lists from all relevant articles and published recommendations for perioperative cardiac risk management were reviewed to identify additional studies. Study Selection and Data Extraction Prospective randomized studies (6) were included in the analysis if they discussed the impact of β-blockade on perioperative cardiac ischemia, myocardial infarction, and mortality for patients undergoing major noncardiac surgery. Articles were examined for elements of trial design, treatment protocols, important biases, and major findings. These elements were then qualitatively compared. Data Synthesis We identified 5 randomized controlled trials: 4 assessed myocardial ischemia and 3 reported myocardial infarction, cardiac, or all-cause mortality. All studies sought to achieve β-blockade before the induction of anesthesia by titrating doses to a target heart rate. Of studies reporting myocardial ischemia, numbers needed to treat were modest (2.5-6.7). Similarly modest numbers needed to treat were observed in studies reporting a significant impact on cardiac or all-cause mortality (3.2-8.3). The most marked effects were seen in patients at high risk; the sole study reporting a nonsignificant result enrolled patients with low baseline risk. As a group, studies of perioperative β-blockade have enrolled relatively few carefully selected patients. In addition, differences in treatment protocols leave questions unanswered regarding optimal duration of therapy. Conclusions Despite heterogeneity of trials, a growing literature suggests a benefit of β-blockade in preventing perioperative cardiac morbidity. Evidence from these trials can be used to formulate an effective clinical approach while definitive trials are awaited.