Blood collection devices, systems, and methods

An access system for use with a base catheter system that includes a base catheter and a hub at a proximal end of the base catheter, the access system comprising:

• a housing comprising an extension at a distal end thereof that is insertable into and removable from the hub of the base catheter system, the housing defining an opening;
• an access catheter of which a first portion is positioned within the housing and a second portion extends out of the housing through the opening when the access catheter is in a retracted position, the access catheter being configured to move relative to the housing from the retracted position to an extended position;
• a stiffener encompassing at least a portion of the second portion of the access catheter, the stiffener being graspable at an exterior of the housing for application of force thereto to advance the access catheter from the retracted position to the extended position;
• and
• a fitting coupled to the second portion of the access catheter,
• wherein, when the extension of the housing is inserted into the hub of the base catheter system, the first portion of the access catheter is advanceable through the extension of the housing, through the hub, and through at least a portion of the base catheter as the access catheter is advanced to the extended position.