Fig. 1. Algorithm for central venous insertion and verification. This algorithm compares the thin-wall needle (i.e. , Seldinger) technique versus  the catheter-over-the needle (i.e. , Modified-Seldinger) technique in critical safety steps to prevent unintentional arterial placement of a dilator or largebore catheter. The variation between the two techniques reflects mitigation steps for the risk that the thin-wall needle in the Seldinger technique could move out of the vein and into the wall of an artery between the manometry step and the threading of the wire step. ECG = electrocardiography; TEE = transesophageal echocardiography.