• Highest recorded "sustainable" blood flow (ml/min) pre- and post- thrombolytic administration. [ Time Frame: 4 hours ] [ Designated as safety issue: No ]
• Change in Kt/V from the treatment before thrombolytic administration compared to the treatment after thrombolytic administration. [ Time Frame: 72 hours ] [ Designated as safety issue: No ]
• Change in "litres processed / time" from the treatment before thrombolytic administration compared to the treatment after thrombolytic administration. [ Time Frame: 72 hours ] [ Designated as safety issue: No ]
• Serious adverse events including major bleeding within 24 hours of alteplase administration [ Time Frame: 30 days post-last dose ] [ Designated as safety issue: Yes ]

• Highest recorded “sustainable” blood flow (ml/min) pre- and post- thrombolytic administration.
• Change in Kt/V from the treatment before thrombolytic administration compared to the treatment after thrombolytic administration.
• Change in “litres processed / time” from the treatment before thrombolytic administration compared to the treatment after thrombolytic administration.
• Serious adverse events including major bleeding within 24 hours of alteplase administration

We are investigating a new way of administering alteplase to remove clots from hemodialysis catheters. Currently, alteplase is left to dwell inside the catheter between dialysis treatments to dissolve the clot and restore blood flow through the catheter. We have developed a new way to administer alteplase by advancing it to the tip of the catheter at regular 10 minute intervals. We hypothesize that our new "push" protocol will dissolve clots in hemodialysis catheters better and faster than the current dwell method.

Central venous catheters are commonly used for vascular access in the hemodialysis population. A common complication is low / no blood flow through the catheter due to clots. These are serious situations because patients may miss dialysis sessions and suffer significant morbidity. In an attempt to dissolve the clots and restore blood flow, thrombolytics are frequently instilled into the catheters between dialysis sessions . However, we have developed and new "push" protocol that advances fresh thrombolytic (alteplase) to the tip of the catheter in order to facilitate more effective and faster removal of the clot. We hypothesize that our new "push" protocol will dissolve clots in hemodialysis catheters better and faster than the current dwell method.

• Drug: Alteplase "push" protocol
• Drug: alteplase dwell arm

• Active Comparator: Alteplase used by normal dwell procedure
• Experimental: Alteplase given by an new "push" protocol

Inclusion Criteria:

1. Adults > 18 yrs old
2. Hemodialysis patients
3. Vascular access with a permanent catheter
4. No prior rt-PA use in the catheter over the previous 21 days
5. One rt-PA instillation per catheter (i.e. we will only document the results of 1 rt-PA instillation per catheter. Numerous rt-PA instillations in the same catheter will NOT be considered new events, and not entered into the study)

Exclusion Criteria:

1. Critically ill patients in the ICU setting.
2. Contraindications / cautions with alteplase use including: known hypersensitivity to alteplase or its components (l-arginine, phosphoric acid, polysorbate 80), patients with known conditions associated with bleeding events (e.g.intracranial bleed in last 4 weeks, major hemorrhage in last 4 weeks (Hgb drop of 20 g/L)), recent surgery (<48 hours), recent biopsy (<48 hours), hemostatic defects including severe hepatic disease, or current intracranial / intraspinal neoplasm.
3. Hemodialysis catheter has been in the patient less than 14 days.