Beta blockers may increase risk of anemia-induced adverse cardiovascular events

Routinely used to treat patients for heart attack or high blood pressure, beta blockers are known for their role in helping to protect the heart. A new study in the January issue of the journal Anesthesiology looks at the effects of beta blockers on surgical outcomes, revealing that the cardioprotective effects of the medication could be compromised by acute surgical anemia.

Blood loss and anemia are very common in patients during and after surgery; more than 30 percent of patients undergoing moderate- to high-risk surgery experience a significant drop in blood levels. The normal response of a patient's body during significant blood loss is to increase cardiac output through increased heart rate to ensure sufficient delivery of oxygen to organs.

Beta blockers are used to treat a variety of conditions, including high blood pressure, heart attack, glaucoma and migraines. The medication works to reduce the heart rate, reducing blood pressure as a result. Beta blockers are often prescribed for patients around the time of surgery to provide protection of the cardiovascular system.

"Beta blockers are known to reduce death from cardiac complications after noncardiac surgery and have been recommended for patients with clinical risk factors. However, previous studies such as the POISE (Perioperative Ishemic Evaluation) trial published in the May 31, 2008 Lancet have revealed that increased stroke rates and mortality were associated with blood loss in patients treated with high doses of beta blockers," said W. Scott Beattie, M.D., Ph.D., F.R.C.P.C., Fraser Elliot Chair in Cardiac Anesthesia, University Health Network, Toronto General Hospital in Toronto, Ontario, Canada.

Dr. Beattie further explained, "The natural response of the body to blood loss and the action beta blockers induce on the body create a paradox for treatment. Blocking the appropriate response of the body to anemia, as would happen with patients who are on or in need of beta blockers, may actually increase the risk of anemia-induced adverse cardiovascular events. "