Primary objective: To compare the decrease in systolic blood pressure between hydration and venous contention when switching to a standing position. Hypothesis in that hydration is better than venous contention.

Secondary objective: To evaluate the effect of hydration on lowering systolic blood pressure during the passage standing in elderly patients with orthostatic hypotension.

Inclusion criteria: Patient aged over 75 years old with orthostatic hypotension proved to 1 and / or 3 min

Day 0: confirmation of the orthostatic hypotension, without prevented measures

Two groups randomized :

• Group 1: First day (day 1), Orthostatic Hypotension test after hydration by three large glasses of clear liquid (33cl). Second day (day 2), Orthostatic Hypotension test with venous contention in the morning.
• Group 2: First day (day 1), Orthostatic Hypotension test after implementation of venous contention in the morning. Second day (day 2), Orthostatic Hypotension after hydration by three large glasses of clear liquid (33cl).

Inclusion Criteria:

• Patient aged 75 and older with orthostatic hypotension proved to 1 and / or 3 minutes.
• Written consent of the subject
• Hospitalization or stay expected minimum 3 days
• Affiliation to a social security scheme

Exclusion Criteria:

• bedridden patient or without possibility of verticalization
• Patient who can't stand up (pulmonary embolism with high risk)
• Patient who refuse to participate in the study
• Patient with legal protection
• State or condition that may affect the stability of blood pressure during the study (hyperthermia, modification antihypertensive treatments less than 48 hours before inclusion...)
• Pathology preventing hydration: Heart failure with less than 1 Liter water restriction, swallowing disorders preventing hydration orally, inability to nutrition and hydration orally
• Intravenous or subcutaneous hydration (intravenous or subcutaneous treatments not included)
• Patient who can't have venous contention: Blue phlebitis, septic thrombosis, arteritis with score less than 0.6, varicose ulcers during treatment