Inclusion Criteria:

- Must give written informed consent

- Ages 18 or older

- Unable to withdraw at least 3 mL of blood from a central venous access device

- Hemodynamically stable

- Available for follow-up assessments

Exclusion Criteria:

- Inability to infuse at least 2 mL of saline through the catheter

- Catheter placed less than 48 hours prior to detection of occlusion

- Catheter used for hemodialysis or pheresis

- Previous treatment with plasminogen activator for current episode of catheter
occlusion

- Less than 18 years of age

- Any evidence of mechanical or nonthrombotic occlusion

- In the opinion of the investigator, subject is at "high risk" for bleeding events of
embolic complications, or has a condition for which bleeding constitutes a
significant hazard

- Increased risk for drug extravasation

- Pregnant, lactating, or actively menstruating women and women of child-bearing
potential who are not using adequate contraceptive precautions (e.g., intrauterine
device, oral contraceptives, barrier methods, or other contraception deemed adequate
by the investigator)

- Known right-to-left cardiac shunt, patent foramen ovale, or atrial/ventricular septal
defect

- Participation in any other study of an investigational device, medication, biologic,
or other agent within 30 days before enrollment and until the 30-day follow up visit

- Any other subject feature that in the opinion of the investigator should preclude
study participation