Correct Tip Position of Central Venous Catheters

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