Beta blockers for elective surgery in elderly patients: population based, retrospective cohort study

Abstract

Objective: To test whether atenolol (a long acting beta blocker) and metoprolol (a short acting beta blocker) are associated with equivalent reductions in risk for elderly patients undergoing elective surgery.

Design: Population based, retrospective cohort analysis.

Setting: Acute care hospitals in Ontario, Canada, over one decade.

Participants: Consecutive patients older than 65 who were admitted for elective surgery, without symptomatic coronary disease.

Main outcome measure: Death or myocardial infarction.

Results: 37,151 patients were receiving atenolol or metoprolol before surgery, of which the most common operations were orthopaedic or abdominal procedures. As expected, the two groups were similar in demographic characteristics, medical therapy, and type of surgery. 1038 patients experienced a myocardial infarction or died, a rate that was significantly lower for patients receiving atenolol than for those receiving metoprolol (2.5% v 3.2%, P < 0.001). The decreased risk with atenolol persisted after adjustment for measured demographic, medical, and surgical factors; extended to comparisons of other long acting and short acting beta blockers; was accentuated in analyses that focused on patients with the clearest evidence of beta blocker treatment; and reflected the immediate postoperative interval.

Conclusions: Patients receiving metoprolol do not have as low a perioperative cardiac risk as patients receiving atenolol, in accord with possible acute withdrawal after missed doses.

Fig 1

Relative reduction in risk of death or myocardial infarction. Relative risk of myocardial infarction or death for patients receiving atenolol compared with patients receiving metoproplol. A x axis value of 0 denotes the null effect, where risk with atenolol equals risk with metoprolol. Values to the right of 0 indicate a relative risk reduction in favour of atenolol. Baseline risk in each analysis shown in parentheses as total number of events and total sample size. Complete cohort analysis appears at the bottom, showing a 23% relative reduction in the risk of myocardial infarction or death for patients prescribed atenolol compared with patients prescribed metoprolol (95% confidence interval 13 to 32). The designated medication subgroups exclude those receiving the corresponding agent. For example, the 15th line shows that for the subgroup of patients not receiving furosemide, atenolol is associated with a 20% reduction in the risk of myocardial infarction or death (9 to 30)

Fig 2

Absolute risk of death in hospital within 30 days of elective surgery. Absolute risk of death comparing atenolol with metoprolol after surgery. Data expressed as cumulative number of deaths per 1000 admissions on corresponding day. P values compare death rate with atenolol relative to metoprolol for entire interval and for consecutive 14 day intervals, using log rank test