Effect of 0.5% vs 0.375% Ropivacaine on Autonomous Nervous System

Comparison of the Effect of Ropivacaine 0.5% vs 0.375% on the Autonomous Nervous System During Shoulder Surgery in Beach Chair Position

It is established that the local anesthetic that is administered during an interscalene block affects the autonomic outflow to the heart. This is very well seen during shoulder surgery when the patient is positioned in beach chair pasition.

The investigators want to study the different effect of the two concentrations (0.5% and 0.375%) of ropivacaine on the autonomic nervous system through blood pressure and heart rate measurements.

Inclusion Criteria:

• Elective shoulder surgery
• Age 18- 80 years old
• ASA I - IV
• Beach chair position

Exclusion Criteria:

• Coagulopathy disorders
• Infection at the puncture site for the interscalene block
• Neurological deficit on the side to be operated
• Allergy to local anesthetics
• Psychiatric disorders
• Patient's refusal
• Problems with patient communication
• Failure of the interscalene block