Beta-Blockers May Increase Mortality After Noncardiac Surgery in Patients With Anaemia: Presented at ASA

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Title: Beta-Blockers May Increase Mortality After Noncardiac Surgery in Patients With Anaemia: Presented at ASA
URL: http://www.pslgroup.com/dg/2314A2.htm
Doctor's Guide
October 23, 2008

By Deborah Brauser

ORLANDO, Fla -- October 23, 2008 -- The probability of mortality or myocardial infarction (MI) increases in anaemic patients who receive beta-blockers, according to research presented here at the American Society of Anesthesiologists (ASA) 2008 Annual Meeting.

Scott Beattie, MD, University Health Network, University of Toronto, Toronto, Ontario, reported the results of this trial -- selected as one of the 10 "Best Abstracts of the Meeting" -- here on October 20.

Since mortality after noncardiac surgery now exceeds 2% in many observational databases, the American Heart Association and American College of Cardiology recommended perioperative beta-blockade as a way to reduce this trend, reported Dr. Beattie. The recently completed and published Perioperative Ischemic Evaluation (POISE) trial, however, found that beta-blockers actually increase the risk of death, as well as the risk of major stroke.

The purpose of this study then was to evaluate the effects of beta-blockers on patients with chronic and acute perioperative anaemia.

In this retrospective analysis, 5,000 patients who had noncardiac or nontransplant surgery over a 2-year period were reviewed. A propensity score was derived for those administered beta-blockers (n = 707), while a matched cohort was selected of patients who did not receive beta-blockers (n = 707).

The relationship between the administration of beta-blockers, preoperative and postoperative haemoglobin, and death was analysed using logistic regression. The composite outcome of interest combined death at 90 days. The percent change in haemoglobin and the composite outcome in each group were assessed using a cubic spine function in the matched cohort. Statistical Analysis System (SAS) version 9.1 was also used.

At the end of the study, multivariable logistic regression analysis found that beta-blockers and acute perioperative anaemia were independent predictors of the composite outcome of death and MI, with the adjusted odds ratio for beta-blockers at 1.8 (95% confidence interval [CI], 1.4 to 2.2).

In addition, the results showed that every 10% decrease in haemoglobin increased the odds of death and MI by 1.33 (95% CI, 1.19 to 1.9).

When propensity scores were used to match the patients administered beta-blockers to patients with equal risk who did not receive beta-blockers, the odds ratio of the composite outcome for this subgroup was 1.7 (95% CI, 0.97-2.4). The probability of mortality or MI was progressively higher for patients administered beta-blockers when haemoglobin decreased postoperatively more than 30%.

"The bottom line was that acute anaemia is associated with an increase in cardiovascular morbidity in patients receiving beta-blockers," said Dr. Beattie. "There is an urgent need to explore these relationships prospectively in light of the POISE results."

Dr. Beattie said that the 30% drop was especially telling. "Practice guidelines suggest that you can let people go down as low as a haemoglobin [count] of 70 which is about a 50% drop. And it looks like we can't do that, which is probably the most important thing."

"If you just think that you can give someone a beta-blocker and they'll be okay, I think you need to really investigate that now," Dr. Beattie continued. "You need to be very cognizant of all of the effects that heart rate and blood pressure and cardiac opioids have [in order] to intervene that way. Beta-blockers may actually be very cardioprotective if they're used in an appropriate way. I just don't know what 'appropriate' means, but it's something to explore."

[Presentation title: Causes of Mortality After Non-Cardiac Surgery: Interrelationship Between Beta Blockers and Anemia. Abstract 846]

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