An illustrative system includes a catheter with a first conduit having a first distal port. The first distal port is in fluid communication with an interior of a balloon mounted to the catheter. The catheter also includes a second conduit having a second distal port, where the second distal port is configured to receive a needle. The balloon is configured to inflate responsive to a fluid received through the first distal port such that the needle is suitably positioned to penetrate an external surface of a subject.
