‘Sweet Spot’ Identified for BP During Stroke Thrombectomy

When it comes to blood pressure in patients undergoing endovascular therapy for acute ischemic stroke, there appears to be a “sweet spot” associated with the best 90-day functional outcomes, new data show.

In pooled data from three randomized trials, mean arterial BP readings that were lower than 70 mm Hg and greater than 90 mm Hg around the time of the procedure correlated with increased odds of worse modified Rankin Scale (mRS) scores at 90 days, researchers led by Mads Rasmussen, MD, PhD (Aarhus University Hospital, Denmark), report. Spending more time in those ranges seems to result in even poorer outcomes,

Those findings, published online January 27, 2020, ahead of print in JAMA Neurology, suggest that periprocedural BP may be a factor that can be actively modified to improve how patients fare, rather than simply a marker associated with outcomes.

Speaking with TCTMD, Rasmussen pointed out that data informing optimal BP management during stroke thrombectomy has been lacking, which is reflected by silence in practice guidelines. Although he said “you can mostly use this study to generate hypotheses for future studies,” he indicated that it could have an impact on practice in a field devoid of randomized data.

“I think we will change our practice in my institution based on this because it is still the largest study defining specific thresholds, but you need to confirm them,” Rasmussen said.

Bay Leslie-Mazwi, MD (Massachusetts General Hospital, Boston), who has been involved in writing guidelines for the early management of acute ischemic stroke, agreed that these data—though subject to certain limitations—are persuasive.

The study “gives us some of the best—I think you could even argue, the best—available data that we have for large-vessel-occlusion patients and what their blood pressures do,” he said.

By showing that mean arterial pressures that are too low or too high are associated with worse 90-day neurologic outcomes, the findings “give us a range of 70 to 90 mm Hg as that Goldilocks spot, that sweet spot where it’s not too hot and not too cold,” Leslie-Mazwi said, adding that he will change his practice based on the results.

“With this data, at least we have a sense of where the floor and the ceiling should be,” he explained. “It certainly will be enough to modify the way I approach patients. Whether it’s enough to modify things at a systemic level, at a guideline level, [it’s] probably not quite strong enough for that yet.”

Filling the Void

Prior observational studies have shown that use of general anesthesia during endovascular therapy is associated with a drop in BP, and that is believed to contribute to the poorer outcomes seen in the setting of general anesthesia versus procedural sedation.

Three recent randomized trials—SIESTA, ANSTROKE, and GOLIATH—have compared outcomes with general anesthesia versus procedural sedation during endovascular therapy, with all showing no significant differences in terms of neurologic outcomes. All involved strict protocols for BP management.

To see whether specific BP thresholds in the periprocedural period were associated with functional outcomes, Rasmussen et al pooled patient-level data from those three trials. The analysis included 365 patients (mean age 71.4 years; 44.6% women) who had a stroke caused by an occlusion in the anterior circulation. The median NIH Stroke Scale score was 17.

The investigators found a U-shaped relationship when looking at mean arterial BP readings and 90-day mRS scores, with both low and high BP associated with worse functional outcomes. Relationships were stronger for lower pressures.

The key cutoffs were less than 70 mm Hg and more than 90 mm Hg. For example, the odds of having a higher mRS score were increased with the following exposures:

• Cumulative period of at least 10 minutes with a mean arterial BP of less than 70 mm Hg (adjusted OR 1.51; 95% CI 1.02-2.22)
• Continuous episode of at least 20 minutes with a mean arterial BP of less than 70 mm Hg (adjusted OR 2.30; 95% CI 1.11-4.75)
• Cumulative period of at least 45 minutes with a mean arterial BP greater than 90 mm Hg (adjusted OR 1.49; 95% CI 1.11-2.02)
• Continuous episode of at least 115 minutes with a mean arterial BP greater than 90 mm Hg (adjusted OR 1.89; 95% CI 1.01-3.54)

Numbers needed to harm ranged from 4 to 10.

Informing Future Trials

Leslie-Mazwi said that studies like this one take on greater importance as uptake of stroke thrombectomy procedures becomes more optimized. At Mass General, he said, about 91% of patients with a stroke caused by a large-vessel occlusion are getting reperfused, meaning any additional gains will be relatively small. Because of that, managing other variables around the procedure, like BP, becomes key.

It has not been clear up until now whether BP is just a marker of how patients fare after the procedure or if it’s a variable that can be modified to improve outcomes, he noted.

These findings point to the latter possibility and suggest that mean arterial BP may be more important than systolic BP for this purpose, Leslie-Mazwi said. “I think that gives us all a potential future target as we think about blood pressure in these patients.”

There are some caveats to consider when interpreting these results, he pointed out. For one, baseline BP in this study was the last measurement before induction of anesthesia, so any changes that happened before that point would not be captured. In addition, all three trials included in this analysis used strict protocols for managing BP, which means that any patients who had low readings despite that could have been subject to other factors also associated with poor outcomes.

Still, Leslie-Mazwi said, the study “gives us better data than we have had up to this point, and it certainly is going to impact the way that I think about these cases and approach these patients.” Moreover, he said, it provides guidance and adds urgency to the need for randomized trials in this area.

Rasmussen said his group is currently working on plans for a trial that would incorporate the BP thresholds identified in this study. But for now, he said, an important message is that it is crucial to pay attention to BP during these procedures.

“I think that’s basically the most important thing, to have strict blood pressure protocols and really pay attention to your blood pressure management during the thrombectomy procedure because . . . the patients are very sensitive to blood pressure changes, and that has been indicated in quite a few studies before this one,” Rasmussen said.