Acute stroke: low baseline blood pressure equals low seven-day life expectancy?

Abstract

N ormal cerebral autoregulation maintains uniform cerebral blood flow despite fluctuations in cerebral perfusion pressure between 50-150 mm Hg. This autoregulation is impaired during acute stroke resulting in a linear relationship between cerebral blood flow and cerebral perfusion pressure 1 . Elevated systolic blood pressure (SBP) and mean arterial pressure at presentation have been associated with poor outcomes, including early death 1,2,3,4 . There have been few studies that have also shown increased mortality with low SBP at baseline showing a U-shaped curve of mortality with blood pressure 1,5 . These studies have been largely inclusive of minor and severe strokes and there is a paucity of research done to establish an association of mortality and acute blood pressure (BP) in high-risk patients.In this issue of the journal, Furlan et al. 6 report the findings of their single center study among 146 acute stroke patients admitted to the intensive care unit, which examined relationships between BP obtained at presentation and at 48-hours, and the occurrence of early mortality (within seven days). Among the 101 ischemic patients, they observed that baseline systolic BP, baseline diastolic BP, 48-hour mean systolic BP, and 48-hour mean diastolic BP were all significantly lower in patients who died within seven days compared with survivors; and in multiple regression analysis, the 48-hour mean systolic BP remained significantly associated with odds of early mortality. Moreover, a 48-hour mean systolic BP of ≤ 131 mmHg was determined to be the most optimal cut-off for discriminating odds of early mortality. Among the 45 hemorrhagic stroke patients there were no significant associations between BP and occurrence of early mortality.The authors are to be commended for investigating this important yet controversial issue, especially given the plethora of studies over the years that have sought to improve our understanding about how best to manage blood pressure for these patients, taking into consideration the different pathophysiology of the main stroke types (ischemic vs. hemorrhagic), and even subtypes (large vessel occlusion vs. small vessel ischemic disease). Nonetheless, the interpretation of findings observed among their ischemic stroke patients should be looked at carefully.First, information about the various mechanisms of ischemic stroke was not available, although one may presume that since these were all critically ill patients requiring admission into the neurointensive care unit, chances are that the majority had large vessel occlusive disease (although patients with small vessel disease strokes and multiple comorbidities or newonset complications can also find themselves in a critical unit). Ischemic strokes secondary to large artery atherosclerosis may be more prone to hypoperfusion-related extension or recurrence of ischemic stroke than other etiologies of ischemic stroke. This phenomenon was noted in patients with ipsilateral (sub-group analysis of SCAST 7 ) and bilateral severe carotid disease (meta...