Adult, Aged, Analysis of Variance, Dopamine Agonists, Dose-Response Relationship, Drug, Double-Blind Method, Drug Administration Schedule, Emergency Treatment, Female, Fenoldopam, Follow-Up Studies, Humans, Hypertension, Malignant, Infusions, Intravenous, Male, Middle Aged, Probability, Prospective Studies, Reference Values, Severity of Illness Index, Treatment Outcome