Spinal anesthesia is a regional anesthesia method used for surgical procedures generally involving the lower abdominal area, perineum, and lower extremities. Various tests are performed to evaluate the block level after spinal anesthesia, incluyding pinprick test, cold application, and motor examination. These tests are performed to check whether the pain, sympathetic and motor nerve fibers are affected, respectively, after the block; and good communication with the patient is important here. However, it is extremely difficult to evaluate these tests in pediatric, geriatric, mentally retarded or uncooperative patients.

Sympathectomy can be used as a criterion to evaluate the success of the block that occurs after the spinal anesthesia procedure. Sympathetic nerve fibers are the first to be affected by the block, and the success of the block can be evaluated with the revealed sympathectomy. Sympathectomy in the lower extremities after spinal block increases arterial blood flow. This increase in blood flow can be detected by the Pulsed Wave Doppler feature of USG.

Inclusion Criteria:

• Elective surgery under spinal anesthesia
• American Society of Anesthesiologists (ASA) I-II physical status

Exclusion Criteria:

• Contraindication for spinal anesthesia
• ASA physical status >II
• Vasoactive drug usage

Patients scheduled for elective operation with spinal anesthesia will be recruited for the study. Posterior tibial artery velocities (peak systolic, end-diastolic) and the vessel diameters will be measured via USG Pulsed Wave Doppler mode. Three measurements will be performed: before spinal anesthesia, at the 5th and at the 10th minutes after the subarachnoid injection. The patients' sensory and motor examinations will be performed as well.