In this technique, the needle is advanced inside the ultrasound scan plane while observing the long axis of the vein. Unlike the short-axis out-of-plane, puncturing is truly performed in real time. Although this technique can be applied clinically with the Internal Jugular Vein if a small probe is used, it can be difficult to use regular-sized probes on the necks of small adults due to lack of space to manipulate. This technique is particularly useful with the IAV. With the long-axis in-plane technique, penetration of both the anterior and posterior walls of the vein does not occur very often, but the needle may penetrate the vein if the needle is directed from the anterior wall toward one of the lateral walls. Depicting the long axis of the center of the vein can prevent a needle directed toward a lateral wall from penetrating the vein (Fig. 1).