COVID pandemic changed completely the surgical schedule and human resources in our hospital. It was impossible to coordinate the anesthesiologists involved in the study with the kind of patients need for this particular study.

Changes in the vascular tone of anesthetized patients is common and cause hemodynamic problems. The investigators have previously demonstrated that the shape of the pulse oximetry waveform (photoplethysmography) is closely related to the changes observed in systemic vascular resistence. The main change in pulse waveform is based to the dichrotic notch position. The present study was designed to determine if the dichrotic notch position is related to a local or a systemic change in the vascular tone.

This is a prospective and observational study designed to determine if the changes observed in finger photoplethysmographic waveform of surgical patients is related to a local or a sistemic changes in the vascular tone. The investigators will studied 15 patients undergoing regional brachial plexus anesthesia for upper limb surgeries. Photoplethysmography will be continuously recorded in the thumb of the tested hand (anesthetized hand) and in the thumb of the control, opposite hand. Duplex color and power Doppler will measure flow in the both brachial arteries and in the aorta (supraesternal view). The contour analysis of both, photoplethysmogram and arterial flow velocities will be analyzed, correlated and compared.

Inclusion Criteria:

• Written Inform Consent
• Programmed surgery
• Supine position

Exclusion Criteria:

• Emergency surgery
• Peripheral vascular diseases

Patients undergoing regional anesthesia (brachial plexus block) for upper limb surgeries