Inclusion Criteria:  Major patient With acute arterial systolic hypertension over 140mmHg Requiring intravenous administration of one of the two following drugs : Urapidil or Nicardipine  Exclusion Criteria:  Patient ventilated Under Nitrogen Monoxyde Contraindication to Nicardipine or Urapidil Refusal of the patient or his relatives Patient treated for pulmonary hypertension