BP Swings in Acute Stroke Heightens Risk of Early Death

ROCHESTER, Minn., June 28 - Patients with wide swings in blood pressure during the early hours of an ischemic stroke have a higher likelihood of death within three months, said researchers here.

This observation emerged from a study of 71 patients seen in the emergency room within 24 hours of stroke onset, according to Mayo Clinic emergency specialist Latha G. Stead, M.D., and colleagues.

At baseline there were no differences in median systolic or diastolic pressures between the 51 who survived past 90 days and the 20 who did not, but those who developed the greatest fluctuations in readings within the first three hours were significantly more likely to die within three months.

"We found that fluctuation in blood pressure early in the course of ischemic stroke is associated with poor 90-day survival," they wrote in the June 27 issue of Neurology. "This effect is independent of prognostic factors such as stroke severity, age, and gender."

"These data suggest that additional studies are needed to clarify the optimal management of blood pressure in the setting of acute ischemic stroke," said Dr. Stead. "Until those studies are performed, health care providers should be careful not to over-treat high blood pressure acutely after ischemic stroke and need to consider urgently supporting blood pressure in those patients in whom the blood pressure is low."

In a previous study, the authors had shown that a single low blood pressure reading at triage-diastolic of less than 70 mm Hg, and systolic of less than 155 mm Hg, or mean arterial pressure of less than 100 mm Hg-was significantly associated with an increased risk for 90-day mortality.

In the current study, they sought to see what acute fluctuations in blood pressure in the early hours of an ischemic stroke meant.

For the 71 patients who presented with ischemic stroke within 24 hours of the onset of symptoms, the investigators took blood pressure readings every five minutes for the duration of each patient's emergency department stay.

They found that baseline median systolic and diastolic pressures were not different for the patients who died within 90 days compared with those who were still alive at that time (P=0.91 for systolic and P= 0.27 for diastolic).

But when they looked at blood pressure differentials during the first 180 minutes, they found significantly greater swings in readings among the 20 patients who died within 90 days of having a stroke, compared with the 51 patients who survived for at least 90 days.

The median differential in diastolic pressures among the patients who died was 44.5 mm Hg, compared with 25 mm Hg for the survivor (Wilcoxon rank sum test, P<0.001). A similar degree of swing was observed with systolic readings. The median systolic differential was 47 mm Hg among patients who died in the first three months, compared with 30 mm Hg for the survivors (P=0.047)

"We believe that the increased mortality observed in this study in those with fluctuating pressures can be attributed to impaired autoregulation," Dr. Stead and colleagues wrote. "We postulate that those patients who kept a more constant BP throughout their emergency department stay had better perfusion of the ischemic penumbra and hence better outcomes."

They acknowledged that their study was limited by its relatively small sample size, and said that a larger study is needed. Such as study would ideally be conducted in conjunction with autonomic testing to document impaired control of BP and heart rate, they added.

They also pointed out that "whereas the baseline characteristics were similar in this group when compared with our overall stroke registry cohort of all consecutive acute ischemic stoke patients presenting to the emergency department, the current study's cohort had a higher initial NIH Stroke Scale, higher incidence of death at 90 days, and a higher incidence of cardioembolic strokes.

This implies that this current subset of patients had more severe strokes, and therefore these data are not necessarily generalizable to all acute stroke subjects."