MedWire News: The putative excess risk for certain peri-operative complications in patients given beta blockers may be caused by the drugs increasing patients’ vulnerability to the effects of anemia, research suggests.
Perioperative beta blockers are given to reduce patients’ risk for myocardial infarction, but previous research has raised the concern that this approach could also increase the risk for perioperative stroke and mortality.
“We would suggest that acute surgical anemia may be a link between these two factors,” Scott Beattie (University of Toronto, Ontario, Canada) and colleagues write in the journal Anesthesiology.
The researchers reviewed surgical records for 4387 non-cardiac, non-transplant patients, 26% of whom received beta blockers within 24 hours of surgery. They matched patients who did and did not receive beta blockers by a propensity score estimating their probability of receiving a perioperative beta blocker.
Within this subgroup of 827 patient pairs, 6.5% of patients given beta blockers versus 3.0% of controls met the primary composite outcome of myocardial infarction, nonfatal cardiac arrest, and in-hospital mortality. This equated to a 2.38-fold risk increase associated with beta blockade.
However, this risk increase was restricted to patients whose hemoglobin levels fell by at least 35% from baseline. Among these patients, the risk increase associated with beta blockade was 3.15-fold.
In an accompanying editorial, Richard Weiskopf (University of California, San Francisco, USA) said: “We cannot yet claim that we know the influence of hemoglobin in the cardiovascular and cerebrovascular events when beta-adrenergic antagonism is instituted before surgery, but Beattie et al give us a pathophysiologically plausible hypothesis.”
He concluded: “Until better data are available, although beta-adrenergic antagonists seem to protect the myocardium of high-risk patients and may well be of lesser or no efficacy for patients at lesser risk, it would seem prudent to avoid those agents that substantially impair the cardiac response to acute severe anemia when that or substantial hemorrhage is anticipated.”
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