When is the best time to resume beta blockade in chronic users after noncardiac surgery to most effectively prevent postoperative atrial fibrillation?
Although this question has been in flux for years, a retrospective cohort analysis concluded that resuming beta blockers before the end of postoperative day 1 is optimal for decreasing the incidence of atrial fibrillation after these procedures.
“In the cardiac surgical population, perioperative beta blockade has been shown to have a clear benefit in terms of preventing supraventricular arrhythmias,” said Ashish Khanna, MD, a staff anesthesiologist and intensivist at the Center for Critical Care, the Cleveland Clinic, in Ohio. “The same is not the case in noncardiac surgery, where the prevention of cardiac complications has not been shown to outweigh the associated risks of hypotension, cerebrovascular events and mortality.”
Nevertheless, a significant percentage of adults presenting for noncardiac surgery are actively taking beta blockers. Such therapy is regularly interrupted in the preoperative period, and often not resumed in a timely manner after surgery.
“So the task for us was to determine the optimal timing of restarting these drugs—timing that would cause more benefit in terms of preventing postoperative atrial fibrillation than harm in terms of the associated risks of beta blockade,” Dr. Khanna said. “Our hypothesis was that restarting beta blockade before the end of postoperative day 1 would be associated with reduced odds of postoperative atrial fibrillation compared with restarting after postoperative day 1.”
To help test their hypothesis, Dr. Khanna and his colleagues obtained data on 8,201 adult beta blocker users who underwent noncardiac surgery and stayed at least two nights after surgery at the institution’s main campus. “The patient cohort was relatively complicated surgery in sicker patients,” he said. “The average age was 65 years, the median surgical duration was about four hours, and the median length of stay was about six days.” Patients with atrial fibrillation prior to the restart of beta blockade were excluded.
The researchers compared patients who did (early) and did not (late) restart a beta blocker by the end of postoperative day 1 on the incidence of postoperative atrial fibrillation after postoperative day 1. They performed a secondary analysis comparing drug resumption at the end of postoperative day 0. Each patient who restarted beta blocker therapy after postoperative day 1 (late) was matched to a maximum of two patients who restarted by the end of postoperative day 1 (early) using exact and propensity-score matching. The matched groups were compared for postoperative atrial fibrillation using a multivariable logistic regression, adjusting for covariables that were still imbalanced after the matching.
Timing Proves Key
As Dr. Khanna reported at the 2017 annual meeting of the American Society of Anesthesiologists (abstract YI03), 4.9% of patients (94/1,924) resuming beta blocker therapy by the end of postoperative day 1 experienced postoperative atrial fibrillation, compared with 7.0% (68/973) of those retaking the agents after postoperative day 1, yielding an early-versus-late odds ratio (OR) of 0.69 (95% CI, 0.50-0.95; P=0.02).
“These results were replicated in a propensity score–adjusted analysis and in an unadjusted analysis,” Dr. Khanna said. “We also performed another sensitivity analysis varying the day of late restart in both groups. All the resulting models were consistent in outcomes.”
Of note, when the same comparison was performed with resumption of beta blockers on the day of surgery, it yielded a postoperative atrial fibrillation rate of 4.9% for patients who restarted beta blockers and 5.8% for those who did not (OR, 0.84; 95% CI, 0.67-1.04; P=0.11;).
“So, where do we stand?” Dr. Khanna asked. “At the end of this analysis, I can safely say that restarting beta blockers before the end of postoperative day 1 in patients that are chronically on these drugs is significantly associated with decreased odds of postoperative atrial fibrillation in a noncardiac surgical population. Importantly, when the restart day was moved to postoperative day 0, the association became nonsignificant.
“The message here is that we’re often very concerned about restarting beta blockers when patients come out of surgery, since that’s a period of hemodynamic instability, fluid shifts andrelated physiological perturbations,” he continued. “So as perioperative physicians, as intensivists and as anesthesiologists, we probably have some breathing room where we can wait and preferably not restart these agents on postoperative day 0. That said, we do need to intervene and restart these drugs before the end of postoperative day 1 to realize the associated benefit that our work has demonstrated. This is an easy intervention—and the only intervention thus far—that can certainly prevent the occurrence of postoperative atrial fibrillation.”
“Do all these patients receive beta blockers until the day of surgery, even the morning of surgery?” asked Gilbert Blaise, MD, professor of anesthesiology at the University of Montreal Hospital Centre.
“This was retrospective data,” Dr. Khanna replied, “so we looked at whether they were on beta blockade at their last clinic visit prior to surgery. Again, there are a lot of questions to be asked, but with retrospective data, this is what we had.”
“Did you have any information on whether patients were taking long-acting or short-acting beta blockers?” asked Duminda Wijeysundera, MD, associate professor of anesthesia at the University of Toronto.
“I like to think that there are more than just a few people who were on long-acting beta blockers,” Dr. Khanna replied. “And that would actually explain why we did not see an effect by postoperative day 0, because likely the patients had enough drug in their system to keep them beta blocked.”