The changes in blood pressure after acute stroke: abolishing the ‘white coat effect’ with 24‐h ambulatory monitoring

OBJECTIVES: To assess the changes in 24-h and casual blood pressure (BP) levels following hospitalization for acute stroke. DESIGN: Prospective study of patients admitted with acute hemispheric stroke and hospitalized controls using casual and 24-h BP monitoring. SETTING: Medical wards in a large teaching hospital. SUBJECTS: Thirty-three patients (median age 77 years, 17 male) and 21 control subjects admitted non-acutely. INTERVENTIONS: All subjects underwent 24-h BP monitoring within 24 h of stroke onset (patients) or admission (controls) and again at 1 week. Casual BPs were recorded over the same period. MAIN OUTCOME MEASURES: The change in BP over the first week in each group. Eleven stroke subjects had 24-h BP monitoring repeated at 6 months. RESULTS: In the stroke group, 24-h systolic BP (SBP) fell by 7 mmHg (95% CI, 0 to 14 mmHg; P < 0.05) and diastolic BP (DBP) by 3 mmHg (95% CI, 0 to 6 mmHg; P < 0.02) over the first week. Mean 24-h BP levels in the control group did not change during this period. However, casual BP recordings fell in both stroke (18/12 mmHg) and control (19/9 mmHg) groups. Stroke subjects followed to 6 months showed no further change in 24-h BP (day 7: 137 +/- 17/79 +/- 13 mmHg; month 6: 138 +/- 16/78 +/- 11 mmHg). CONCLUSIONS: Although there was a large fall in causal BPs seen in both groups there was only a small, but a significant fall in mean 24-h BP over the first week following hemispheric stroke that was not seen in control subjects. Although the 'white coat effect' and admission to hospital play an important part in the high casual BP observed in the days following acute stroke they are unlikely to be the sole factors.