DURHAM, N.C. – Giving patients a class of drugs known as beta-blockers prior to coronary artery bypass surgery improves the outcome of the surgery, according to a study by researchers from Duke University Medical Center, Louisiana State University Health Sciences Center and the Society of Thoracic Surgeons (STS).
Furthermore, the researchers believe that all patients scheduled to undergo bypass surgery – except for those whose hearts are severely weakened – should receive these drugs before surgery. Since only about 60 percent of bypass patients currently receive beta-blockers before surgery, the researchers believe that by working together, cardiologists and surgeons can improve survival rates of their heart patients.
The team's findings are published in the May 1, 2002 issue of the Journal of the American Medical Association.
By blocking the stimulatory effects of the hormones epinephrine and norepinephrine -- the "fight-or-flight" hormones -- beta-blockers reduce heart rate and blood pressure. Beta-blockers have been used for 20 years for different ailments. Cardiologists use them to help treat high blood pressure, chest pain and heartbeat irregularities.
Randomized clinical trials have proven the effectiveness of beta-blockers in improving outcomes for heart patients in general, and for patients undergoing non-cardiac surgery. However, little data exists on the effects of beta-blockers if given to patients just before surgery.
"In our large observational analysis, we found a small but important survival benefit for patients given beta-blockers before bypass surgery," said Duke cardiologist Eric Peterson, M.D., who along with co-investigator LSU heart surgeon T. Bruce Ferguson, M.D., conducted the analysis. "This effect was seen in all types of patients, and those patients who were the sickest received the greatest benefit."
Specifically, patients receiving beta-blockers had a 30-day mortality rate of 2.8 percent, compared to 3.4 percent for those patients who did not. Furthermore, the researchers found no negative side effects from the drug, except for those patients whose heart pumps at 30 percent of its ability or less. For that reason, these patients should not receive beta-blockers, they said.
The timing of giving beta-blockers is not particularly crucial, Peterson said. Patients who are on beta-blockers prior to surgery would derive the protective benefit, while those not taking the drug could receive it shortly before surgery.
"Early in my surgical training at Duke, we'd take patients off beta-blockers for a while before surgery, and now we're finding that they have a protective effect," Ferguson said. "We've come full circle. These results should provide a scientific basis for everyone involved in a patient's care to make sure they receive beta-blockers before surgery."
In the past, it was believed that since beta-blockers lowered heart rate and blood pressure, patients would be at greater risk during surgery.
"While this study did not address the issue of the mechanism of protection, it appears that beta-blockers ‘soak up' or neutralize the increased amount of stress hormones the body secretes in response to the act of surgery," Peterson said.
For their analysis, Ferguson and Peterson consulted the STS-coordinated National Adult Cardiac Surgery Database, which had data on 629,877 patients who underwent bypass surgery at 497 hospitals in the U.S. and Canada between 1996 and 1999. They compared the outcomes of patients who received beta-blockers to those who didn't.
"From 1996 to 1999 we saw that the usage of beta-blockers increased from 50 to 60 percent, and while that is an improvement, there is still a long way to go," Peterson said. "We also found a wide variation among hospitals, with usage rates ranging from 20 to 85 percent."
The researchers view the findings of their analysis as an opportunity to improve survival rates for an already successful surgery, which is performed more than 570,000 times each year in the United States.
"This is an issue to be addressed at all levels of a patient's care – heart patients who could benefit from beta-blockers should be on them even before surgery, and we as surgeons or anesthesiologists should make sure patients receive them if they're not on them already," Ferguson said.
Additionally, the researchers found that patients taking beta-blockers spent less time on mechanical ventilation after surgery and experienced fewer instances of kidney problems.
The researchers point out that this study is an observational analysis and that future randomized trials need to be conducted to refine the findings and to better understand the mechanism of protection.
"One of the most important aspects of this study is that it was conducted with a huge national databank unique to cardiac surgery in conjunction with the Duke Clinical Research Institute, one of the leading research organizations," Ferguson said. "The marriage of this unique database and the DCRI creates opportunities to conduct future studies like this."
The analysis was supported by a grant to the Society of Thoracic Surgeons from the Agency for Healthcare Research and Quality.
Materials provided by Duke University Medical Center. Note: Content may be edited for style and length.
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