Risk factors for hypertensive crisis: importance of out-patient blood pressure control.

OBJECTIVES: The purpose of this study was to identify independent risk factors for development of hypertensive crisis.
METHODS: This was a retrospective, case-controlled study. Cases were 143 patients who presented during a 3-year period to the Emergency Department with the diagnosis of hypertensive crisis, defined as systolic pressure >/=180 mmHg and/or diastolic pressure >/=110 mmHg and symptoms of hypertensive emergency during the Emergency Department presentation. Controls were 485 patients with hypertension, matched to cases on the basis of age, sex and race, who were not admitted to the Emergency Department with an episode of hypertensive crisis during the study period. Co-morbid conditions were identified from computerized health system databases and medical records. Out-patient blood pressures were obtained from medical records from randomly selected out-patient clinic visits.
RESULTS: The average blood pressure during Emergency Department presentation in patients with hypertensive crisis was 197 +/- 21/108 +/- 14 mmHg. Less successful out-patient systolic blood pressure control was an independent risk factor for hypertensive crisis [odds ratio (OR) 1.30 (1.18-1.42), per 10 mmHg, P < 0.001]. Higher out-patient diastolic blood pressures [OR 1.21 (0.99-1.43 per 10 mmHg, P = 0.07] and history of heart failure [OR 3.48 (0.94-12.94), P = 0.06] trended towards independence as risk factors.
CONCLUSION: Less effective blood pressure control, based on out-patient systolic blood pressure measurements, is an independent risk factor for an Emergency Department presentation due to hypertensive crisis.