Blood pressure changes after stroke: abolishing the white-coat effect.

The perfusion pressure in the cerebral capillaries combined with arterial blood pressure creates shear stresses that deform RBCs as they traverse microvessels. Our results show that in cerebral infarction, especially in hypertensive patients, RBCs are more sensitive to lowered shear stresses. Hence, hypotension in acute stroke might induce microcirculatory disorders because capillaries can be wedged by RBCs. It is likely that measurement of the RBC filterability related to perfusion pressure would be helpful for choosing patients who are at risk for cerebral ischemia during lowering of blood pressure. In these patients antihypertensive therapy should be used with caution. References 1. Strandgaard S. The cerebrovascular pharmacology of antihyper-tensive drugs. simple method for measuring erythrocyte deformability. Carlsson and Britton' report that blood pressure (BP) increases in the majority of stroke patients 1 month after discharge from the hospital and suggest that this is due to increased activity out of the hospital setting. In a previous paper,2 they also reported that BP falls in the days immediately after a stroke. However, it is not known to what extent these BP changes are due to an alerting reaction, or "white-coat effect," and how much to a true change in BP. Although a large number of subjects will increase the power of a study to show a significant difference in BP between two periods, it will not necessarily attenuate the white-coat effect-a common phenomenon.3 Reduction or abolition of this effect can be achieved by recording multiple BP readings, preferably taken by a trained nurse rather than a physician, or by using 24-hour nonin-vasive automatic ambulatory BP monitoring. Using the latter method, in 33 conscious subjects (mean age, 77 years) admitted to the hospital with an acute flaccid hemiparesis, we found that mean 24-hour systolic BP fell by 7 mm Hg (95% confidence interval [CI], 0 to 14 mm Hg; P<.05) and mean 24-hour diastolic BP by 3 mm Hg (95% CI, 0 to 6 mm Hg; P<.05) from day 1 to day 6, whereas there was no fall in mean 24-hour BP seen in an in-patient, nonstroke control group of 21 subjects. A subgroup of 11 stroke subjects underwent 24-hour BP monitoring at home 6+3 months after stroke. They exhibited a fall in BP while in the hospital (seen also in the whole stroke group) but there was no further change in mean 24-hour BP from day 6 to month 6 (day 1, 152+16/84+14 mm …