An access system and guided endovenous (100, 110) comprising: an elongated flexible member (112) adapted and configured to access the venous vasculature of a patient, a sensor (115, 1415) disposed at a distal end ( 113) of the elongated and shaped flexible part paraproporcionar ultrasound information in vivo non-image based venous vasculature of the patient a processor (150, 160) configured to receive and process the ultrasound information in vivo not based enimágenes provided by the sensor and to provide an output from the position of the end distalde the flexible elongate member within the venous vasculature of the patient with respect to a predetermined pluralidadde within the venous vasculature of the patient position and an output device (50, 170) adapted to issue the position information provided by the processor, wherein the one of a plurality of predetermined positions within the seselecciona venous vasculature from the group consisting of a location in the lower third of positions the superior vena cava, one unióncavo-auricular, a junction between two or more blood vessels, suggesting a connection between the superior vena cava and the inferior venacava.Un sistema de acceso y guiado endovenoso (100, 110), que comprende: una pieza flexible alargada (112), adaptada y configurada para acceder a la vasculatura venosa de un pacienteun sensor (115, 1415) dispuesto en un extremo distal (113) de la pieza flexible alargada y configurada paraproporcionar información ultrasónica in vivo no basada en imágenes de la vasculatura venosa del pacienteun procesador (150, 160) configurado para recibir y procesar la información ultrasónica in vivo no basada enimágenes proporcionada por el sensor y para proporcionar una salida respecto a la posición del extremo distalde la pieza flexible alargada dentro de la vasculatura venosa del paciente con respecto a una de una pluralidadde posiciones predeterminadas dentro de la vasculatura venosa del paciente y un dispositivo de salida (
