Sonographic Safety Margins of Subclavian Vein: Effect of View and Arm Position

The purpose of this observational study is to evaluate and compare the anatomical safety margins of the subclavian vein using ultrasound. Medical professionals commonly use the subclavian vein to insert central venous catheters, but nearby vulnerable structures, such as the lung and artery, can be at risk during the procedure. This study investigates two different ultrasound probe positions: supraclavicular (above the collarbone) and infraclavicular (below the collarbone). It also examines how changing the patient's arm position (from resting in a neutral position to being raised at a 90-degree angle) affects the distance between the vein and these vulnerable structures. Participants are adult patients scheduled for surgery under general anesthesia who already require ultrasound-guided vascular access. Immediately after falling asleep from anesthesia, researchers will perform a brief 3 to 5-minute ultrasound scan of the collarbone area. This is a strictly non-invasive imaging study; no research-related needle punctures or catheter insertions will be performed. The findings aim to provide robust anatomical evidence to make future vascular procedures safer for patients.

Inclusion Criteria: * Patients requiring ultrasound-guided vascular procedures. * Age between 20 and 79 years. * Patients who have voluntarily provided written informed consent for this clinical study. * American Society of Anesthesiologists (ASA) physical status classification I, II, or III. Exclusion Criteria: * Anatomical variations of the clavicle (e.g., history of clavicle fracture). * Suspected thrombosis at the target site. * Known anatomical abnormalities of the subclavian vein or artery. * Inability to abduct the arm (e.g., due to shoulder joint abnormalities). * Patient refusal to participate.