A vascular access device may include a blood circuit having an arterial blood line and a venous blood line. The venous blood line is connected to a first access needle and the arterial blood line is connected to a second access needle. The venous blood line is connected to an access component affixed to the second access needle and configured such that when the second access needle is used to infuse blood into a patient, the access component is positioned to withdraw blood and convey it into the venous line. The withdrawn blood may also be conveyed to an air detector to detect withdrawal of the second access needle.
