Patients, ages between 18-70 years, who require central venous catheter will be enrolled for the study. Central venous catheter will be inserted using patient's height formula by Seldinger technique. Anterioposterior chest radiography will be used to assess the correct tip position. Catheters that are below the carina more than 1 cm, will be pulled back for repositioning. Catheters that are above the carina more than 1 cm, will be changed by another catheter. The investigators aim to evaluate the formula for correct tip positioning for central venous catheters

Central venous catheters are used for fluid infusion, nutrition, blood transfusion, hemodynamic monitorization in both intensive care unit and operating room. The superior vena cava and right atrium (SVC-RA) junction is considered the optimal position for central venous catheter tip. Carina corresponds to the SVC-RA junction on chest radiograph. Catheter tips, 1 cm above and 1 cm below the carina are considered as the correct position. 18-70 years old patients will be enrolled for the study. Central venous catheters will be inserted via internal jugular vein or subclavian vein using patient's height formula by Seldinger technique. Postprocedural (within 6 hours) chest radiograph will be used to evaluate the correct tip position from the Picture Archiving and Communication System. This formula was described by Peres. If the tip of the catheter is below the carina more than 1 cm, it will be pulled back for repositioning. If the tip of the catheter is above the carina more than 1 cm, another catheter will be inserted. The formula is height (cm)/10 for right internal jugular vein, height(cm)/10-2 for right subclavian vein, height(cm)/10+4 for left internal jugular vein and height(cm)/10+2 for left subclavian vein. Number of the correct and incorrect position of central venous catheter tips will be noted.

The investigators aim to evaluate the reliability and efficiency of Peres' formula for the correct tip position.

Inclusion Criteria:

• Central venous catheterization of patients, ages between 18 and 70

Exclusion Criteria:

• Patient's refusal
• Pathology of carotid artery
• Anatomical deformity of the neck (scar, mass effect, multiple central venous catheterization)
• Chest deformities (pectus excavatum, pectus carinatum)

Patients in intensive care unit and operating room who require a central venous catheter (right or left-sided) will be enrolled for the study.