Central Venous Catheterization is a common procedure in daily clinical practice. The internal jugular, subclavian and the femoral veins are the most frequently catheterized central veins. Pneumothorax, hematothorax, arterial puncture, hematoma, nerve lesions, damage to the left thoracic duct, and air embolism are among the main mechanical complications. Nowadays, there are two techniques in daily clinical use: the traditional technique and the ultrasound guided technique.The traditional technique relies on the use of anatomical landmarks, but the failure rate is high-even in experienced hands. Furthermore, several different complications range from mechanical problems (5-19% of cases) to infections and thrombotic events (2-26%). There is compelling evidence that ultrasound-guided CVC insertion via the internal jugular veins is associated with higher success rates and fewer mechanical complications compared with the traditional techniques based on external anatomical landmarks.We report a clinical case of 76-years-old female patient requiring urgent placement of a central venous catheter and unrecognized arterial puncture and subsequent heparin overdose with nearly fatal outcome.eral venous access, administration of parenteral nutrition, vascular access in patients whose peripheral veins are difficult to catheterize, and procedures that require access to large-caliber vessels [1]. The central vessels that are most frequently catheterized are the internal jugular, subclavian, and femoral veins.The traditional CVC insertion technique relies on the use of anatomical landmarks rather than ultrasound guidance. But even in experienced hands, the traditional technique is associated with a high failure rate and several complications ranging from mechanical problems (5-19% of cases) to infections and thrombotic events (2-26%) [1][2][3][4].Pneumothorax, hematothorax, arterial puncture, hematoma, nerve lesions, damage to the left thoracic duct, and air embolism are among the main mechanical complications [5]. The incidence of complications increase 6-fold after the third insertion attempt [1]. Other risk factors that are known to increase the incidence of complications are an inexperienced operator, the presence of anatomical variants as well as co-existing medical conditions such as clotting disorders, pulmonary emphysema, hypovolemia, or difficulties related to conditions under which the procedure is performed (i.e. an emergency) [5].