Boston, MA - Perioperative treatment with beta blockers in patients undergoing major noncardiac surgery greatly lowered in-hospital mortality among those predicted to be at highest risk "but was of no benefit—and was possibly harmful—to patients in the lowest-risk categories," according to a retrospective cohort study [1].

The results, which build on previous observations, "provide support for the perioperative use of beta blockers in high-risk patients" pending the outcome of prospective trials currently exploring the technique, write Dr Peter K Lindenauer (Baystate Medical Center, Springfield, MA) and colleagues in the July 28, 2005 issue of the New England Journal of Medicine.

"Yet the lack of benefit of this approach in moderate-risk patients and the potential for harm from this approach in the lowest-risk groups suggest that careful patient selection remains necessary," the group writes.

Of 663 635 beta-blocker-eligible patients who underwent noncardiac surgery at 329 predominantly nonteaching hospitals in the US, 18% received the drugs perioperatively. Overall, beta blockade was not significantly associated with in-hospital mortality.

Beta blockers appeared to be harmful in low-risk patients, neutral in patients at intermediate risk, and beneficial in high-risk patients.

But varying outcomes emerged when patients were assigned a score, from 0 to 5, based on the Revised Cardiac Risk Index (RCRI). The score corresponded to the number of certain surgical risk factors: high-risk surgery, ischemic heart disease, cerebrovascular disease, renal insufficiency, and diabetes. Beta blockers were used in about 14% of those with no risk factors and in 44% of those with at least four (RCRI scores 0 and >4, respectively).

Adjusted mortality risk was compared with RCRI score for the entire cohort and with a subset cohort, which consisted of 119 632 beta-blocker recipients and 216 290 non-beta-blocker recipients matched on the basis of patient features and risk factors. Mortality risks observed in the latter "propensity-matched" analysis were similar to those from the overall cohort, except that an RCRI score of 2 in the larger cohort corresponded to significantly reduced in-hospital mortality, according to the authors.

"Beta blockers appeared to be harmful in low-risk patients, neutral in patients at intermediate risk, and beneficial in high-risk patients," observed Drs Don Poldermans and Eric Boersma (Erasmus Medical Center, Rotterdam, the Netherlands) in an accompanying editorial [2]. They describe how limitations in the study's design, many of which Lindenauer and colleagues describe in detail, make it hard to interpret the results. And because no interaction between beta blockers and CV risk factors has been observed before, they write, "it is hard to explain why beta blockers would not confer protection in patients with a limited number of risk factors . . . but would do so if one or two additional risk factors were present."

However, "the apparent beneficial effect of beta blockers in high-risk surgical patients in the present study, coupled with earlier reports of such benefits in small randomized trials, supports the routine use of beta blockers in high-risk patients undergoing noncardiac surgery," according to the editorialists. But until ongoing trials clarify the issue, they write, low- or intermediate-risk patients should not routinely be considered for perioperative beta-blocker therapy at noncardiac surgery. They make an exception for patients already on beta blockers, "given the potential cardiac risks associated with the sudden interruption of beta-blocker therapy."