A system and method facilitate percutaneous intravascular access while militating against unwanted penetration of the accessed blood vessel. A small diameter access tube includes a terminal segment comprised of a shape memory polymer and configured to flare outwardly toward a larger diameter orifice. The configuration of the terminal segment is modified to taper toward the insertion point of an internal insertion needle for facilitating insertion of the access tube into a blood vessel. Subsequent to insertion, the access tube is advanced relative to the insertion needle which then is retracted, and the terminal segment is allowed to return to the flared configuration so that fluid flow through the access tube is facilitated.
