The main objective is to determine if dexmedetomidine combine with alfentanil allow a level of conscious sedation within maximum security conditions in an emergency department.

Patients included in the study will receive an injection of dexmedetomidine via a TIVA Injectomat Agilia, specially programmed for the injection of dexmedetomidine.

Patients will also receive a dose of alfentanil, 1 minute before the technical act.

Inclusion Criteria:

Adult over 18 years, of both sexes, for which a procedural sedation is needed in emergency room. The rules for sedation, in accordance with the international guidelines, are:

• The insertion of a chest drain
• Abscess incision and drainage
• Closed reduction of a dislocated joint

Exclusion Criteria:

• Patients refusing to participate in the study (refusal to sign the consent form)
• Patients refusing sedation
• Patients unable to participate in the study (consent is impossible to obtain)
• Pregnant women
• The hypersensitivity to the active ingredient, dexmedetomidine hydrochloride.
• Patients with poor respiratory status determined by:

Respiratory rate > 30 / min Oxygen saturation <90%

• Patients with unfavorable hemodynamic status determined by :

A heart rate > 120 / min A heart rate < 50 / min Systolic blood pressure ≥ 180 mmHg or ≤100mmHg Diastolic blood pressure ≥ 110mmHg

• Patients with contraindication to the use of dexmedetomidine :

Advanced heart block (level 2 or 3) unless pacemaker Acute cerebrovascular disease