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Abstract

A catheter assembly is provided. An attachment structure has a proximal end portion of an outer cannula attached to it. A needle is insertable through the outer cannula and the attachment structure. An inner cannula is attached to an inner cannula attachment region of the attachment structure. The inner cannula is insertable axially through the attachment structure. The attachment structure can comprise two hubs, one for the outer cannula and the other for the inner cannula, the two hubs being attachable to one another to form the overall attachment structure. A valve structure is associated with the attachment structure, suitably with the outer cannula hub. The valve structure normally closes communication between an access passage in the attachment structure, e.g., in the outer cannula hub, and the outer cannula lumen. The valve structure opens sufficiently for the inner cannula to pass through it and to open communication between the access passage and the outer cannula lumen when the inner cannula is inserted through another passage in the attachment structure and through the outer cannula lumen. The assembly allows the removal of the inner cannula and the insertion of a replacement inner cannula, if desired, without removing the outer cannula from the blood vessel. Use of a relatively small diameter needle for a desired diameter outer cannula can also be provided if the material of the outer cannula is such that it will swell in place.

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