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POISE-2 was the largest clinical trial to address major cardiovascular complications in non-cardiac surgery. The factorial trial randomized 10,010 patients in 23 countries to low-dose clonidine vs placebo and to low-dose aspirin vs placebo. The primary end point was death or nonfatal myocardial infarction (MI) at 30 days.
Patients randomized to clonidine were given 0.2 mg orally before surgery and daily transdermal patches that continued to deliver 0.2 mg/day for 72 hours after surgery. The control group received placebo pills or patches.
At 30 days, clonidine had not improved the primary outcome of mortality and nonfatal MI. In fact, a non-significant increase in MI was seen in the clonidine group, compared with placebo (329 vs 295). However, 48 percent of patients in the clonidine group experienced clinically important hypotension, vs 37 percent of placebo patients, and rates of nonfatal cardiac arrest were significantly greater in those taking clonidine (16) than placebo (5).
In the aspirin arm, patients taking aspirin daily for four of the six weeks before surgery were separated from those who did not take aspirin. Aspirin use was stopped 72 hours before surgery in all patients. Patients were then given 200 mg of aspirin immediately before surgery. After surgery, patients who had taken aspirin regularly before surgery took 100 mg or placebo for seven days, then resumed their prior aspirin regimen. Those who had not taken aspirin before surgery took 100 mg of aspirin or placebo for 30 days.
At 30 days, the rate of death or nonfatal MI was 7 percent in the aspirin group and 7.1 percent in the placebo group. However, aspirin-treated patients experienced significantly more clinically important bleeding, affecting 4.6 percent, compared with 3.8 percent in the placebo group.
About one-third of patients are taking aspirin when they enter the hospital for surgery, and the trend is to continue the aspirin through surgery. The authors recommend stopping this practice.
“It is clear from the POISE-2 results that aspirin should be discontinued, as it does not prevent MI and does promote serious bleeding,” says Cleveland Clinic’s Daniel I. Sessler, MD, coauthor of the study, which was published in the April 17, 2014, New England Journal of Medicine.
“Patients who have had an infarction should presumably be started on aspirin and statins, if they do not already take the drugs — although neither treatment has been specifically tested in this context,” he adds.
A way of preventing postoperative MI has not yet been identified, but avoiding hypotension during and—and particularly after—surgery is likely critical, he says.
“A future study might seek to evaluate a drug that prevents tachycardia without causing much reduction in blood pressure,” he suggests.
Dr. Steven Nissen, Chairman of the Department of Cardiovascular Medicine at Cleveland Clinic, suggests that patients with a strong indication for aspirin should be managed individually since “there may be populations in which stopping aspirin is more risky than continuing this therapy.”
Poise demonstrates clearly that the search for a safe, effective way to protect high-risk heart patients from cardiac complications after non-cardiac surgery must continue.