Prophylactic beta-blockade to prevent myocardial infarction perioperatively in high-risk patients who undergo general surgical procedures.

Introduction: The benefit of administering beta-adrenergic blocking agents perioperatively to surgical patients at high risk for myocardial ischemia has been demonstrated in several well-designed randomized controlled trials. These benefits have included a reduction in the incidence of myocardial complications and an improvement in overall survival for patients with evidence of or at risk for coronary artery disease (CAD). We designed a retrospective study at the Ottawa Civic Hospital to investigate the use of beta-blockers in the perioperative period for high-risk general surgery patients who underwent laparotomy and to explore the reasons for failure to prescribe or administer beta-blockers when indicated.

Methods: All 236 general surgery patients over the age of 50 years who underwent laparotomy for major gastrointestinal surgery between Jan. 1, 2001, and Dec. 31, 2001, were assigned a cardiac risk classification using the risk stratification described by Mangano and colleagues. The perioperative prescription and administration of beta-blockers were noted as were the patient's heart rate and blood pressure parameters for the first postoperative week, in-hospital adverse cardiac events and death.

Results: Of the 143 patients classified as being at risk for CAD or having definite evidence of CAD, 87 (60.8%) did not receive beta-blockers perioperatively. Of those who did, 43 were previously on beta-blockers and 13 had them ordered preoperatively. Patients with definite CAD were significantly more likely than others to receive beta-blockers perioperatively (p < 0.001), as were patients seen by an anesthesiologist or an internist preoperatively (p < 0.001). Twenty (33%) of the 61 patients who were already taking beta-blockers preoperatively had them inappropriately discontinued postoperatively. Once prescribed by the physician, beta-blockers were administered by the nurses irrespective of nil par os status. The mean heart rate and blood pressure parameters for patients receiving beta-blockers postoperatively was 82 beats/min and 110 mm Hg, respectively, and these values were not significantly different from the mean heart rate of patients not receiving beta-blockers. The number of postoperative cardiac events was significantly higher in patients with definite evidence of CAD, and among this group, the use of beta-blockers was associated with a significant reduction in postoperative cardiac events. This was not true for patients at risk for CAD or patients with no risk of CAD.

Conclusions: A significant proportion (> 60%) of general surgery patients who were identified as having definite evidence of, or being at risk for, CAD were not prescribed beta-blockers preoperatively. More than 30% of patients who were on beta-blockers preoperatively did not have them reordered postoperatively. These results may reflect controversy surrounding the recommendations, miscommunication between surgeons and anesthesiologists and errors in postoperative ordering.