The aim of this study is to evaluate the effect of leg elevation on the prevention of intraoperative hypotension during shoulder surgery in the Beach-chair position. patients undergoing shoulder surgery in the Beach-chair position will be randomly assigned to Group L (with leg elevation) or Group C (no intervention). The primary outcome is the incidence of intraoperative hypotension (mean blood pressure < 60mmHg or systolic blood pressure < 80% of baseline). Secondary outcomes are the incidence of intraoperative cerebral desaturation (cerebral oxygen saturation < 80% of baseline, longer than 30 seconds), total amounts of administered inotropic agents, and systolic blood pressure, heart rate, and cerebral oxygen saturation at various time points.

Inclusion Criteria:

• adult patients undergoing shoulder surgery in the beach chair position

Exclusion Criteria:

• Patients with myocardial infarction
• Patients with pacemaker
• Patients with cerebrovascular disease
• patients with arteriovenous fistula at the opposite arm
• Patients with autonomic nerve disorders
• Patients with hip or knee joint disorder limiting hip or knee flexion
• BMI > 30 kg/m2

IPD will be made available after article publication, for 3 years from the study completion.

Proposals should be directed to the corresponding author and will be reviewed by the study group. Only requests that have a methodologically sound proposal and whose proposed use of the data has been approved by the independent review committee will be considered.