Both low and high levels of blood pressure during endovascular treatment of acute ischemic stroke are associated with poor functional outcome, a new study suggests.
“Our study has very clinically relevant findings — that best outcomes are achieved if the mean arterial blood pressure [MABP] is kept between 70-90 mm Hg,” lead author, Mads Rasmussen, MD, PhD, Aarhus University Hospital, Denmark, told Medscape Medical News.
“Our main message is that strict blood pressure protocols are needed during endovascular therapy for stroke,” Rasmussen said. “We need be meticulous about blood pressure management during this procedure as patients are very sensitive to blood pressure changes. If we do not manage blood pressure well during the procedure, then this can have a meaningful adverse impact on outcomes.”
The study was published online in JAMA Neurology on January 27.
It’s known that blood pressure drops transiently during the endovascular procedure and previous studies have suggested that low blood pressure adversely affects outcomes, “but we haven’t known what the blood pressure threshold is and for how long it can go below this threshold,” Rasmussen explained.
“This is what we set out to look at in this study,” he said. “We also wanted to see if there was an upper threshold for blood pressure related to outcomes.”
For the current study, the researchers analyzed data from three randomized controlled trials in a total of 380 patents investigating anesthetic strategy during endovascular treatment for stroke.
“One of the main strengths of our analysis is that all the three studies we used had strict blood pressure protocols in place. This has not been the case in previous studies that have tried to investigate the effect of blood pressure on outcomes,” Rasmussen noted.
Results showed that a cumulated period of a minimum 10 minutes with less than 70 mm Hg MABP was associated with a shift toward a higher 90-day modified Rankin scale (mRS) score (adjusted odds ratio [OR], 1.51; 95% confidence interval [CI], 1.02 – 2.22) and a number needed to treat to harm 1 patient of 10.
A continuous episode of a minimum 20 minutes with less than 70 mm Hg MABP had a higher risk of an increased 90-day mRS score (adjusted OR, 2.30), corresponding to a number needed to treat to harm 1 patient of 4.
At the other end of the spectrum, a cumulated period of a minimum 45 minutes with greater than 90 mm Hg MABP was associated with a shift toward a higher 90-day mRS score (adjusted OR, 1.49), corresponding to a number need to harm of 10.
And a continuous episode of a minimum 115 minutes with greater than 90 mm Hg MABP showed a greater risk of a higher mRS score (adjusted OR, 1.89), corresponding to a number needed to harm of 6.
“These results suggest These results suggest MABP may be a modifiable therapeutic target to prevent or reduce poor functional outcome in patients undergoing [endovascular treatment] for [acute ischemic stroke] and that MABP should possibly be maintained within such narrow limits,” the authors conclude.
“I would say though, that from our data, mean arterial blood pressure should be kept between 70 and 90 mm Hg. There are bound to be the occasional drops below 70 mm Hg, but these should be kept to a minimum if possible,” Rasmussen commented.
“This is the best data we have so far on optimum blood pressure levels during endovascular treatment for stroke, but it still needs confirmation if possible in a randomized trial,” he added.
Rasmussen noted that this is the first study to have shown that higher levels of blood pressure may also lead to poor outcomes during endovascular treatment, although the relationship is much weaker than that for low blood pressure.
“Our results confirm that the previously established U-shaped blood pressure pattern is also relevant in stroke patients undergoing endovascular treatment,” he stated.
“We used mean arterial blood pressure. Other studies have used systolic blood pressure, and some have suggested that this should kept above 140 mm Hg. Mean arterial blood pressure takes into consideration both systolic and diastolic levels. Further studies are needed to give information on which measurement is best,” he added.
In the paper, the authors say their findings suggest that MABP is more sensitive than systolic pressure in the assessment of hypertension and hypotension.
“Cerebral perfusion pressure, defined as the difference between MABP and intracranial pressure, is considered the physiologic driving force behind cerebral blood flow. Furthermore, MABP is a combination of systolic and diastolic blood pressures and is considered a more valid index of tissue perfusion,” they write.
“We hypothesize that a MABP threshold is a more appropriate indicator of hypertension and hypotension during [endovascular treatment] for [acute ischemic stroke],” they conclude.
Rasmussen was supported by a grant from the Health Research Foundation of Central Denmark Region and the National Helicopter Emergency Medical Service Foundation, Denmark. The remaining study authors’ disclosures are listed in the paper.
JAMA Neurol. Published online January 27, 2020. Abstract