# Blocked central line or port: assessment and clearing with a thrombolytic

Source: https://onco.cc/protocols/central-line-occlusion-management/  
OnCo record `central-line-occlusion-management` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

If your line or port will not give blood back or will not flush, the nurse first checks for simple causes such as a kink, a closed clamp or a needle that has slipped. If a clot is the likely cause, a small dose of clot-dissolving medicine can be left in the line for half an hour to two hours. It should never be forced.

## Summary

Occlusion is partial (fluid goes in but blood will not come back) or complete. ESMO (2015) groups causes as mechanical (a kink, a tight suture, a dislodged or blocked port needle, the tip against the vein wall, pinch-off between the first rib and clavicle), thrombotic (fibrin sheath, clot in the lumen, mural or venous thrombosis) and drug-related (precipitates from incompatible drugs or parenteral nutrition). The alteplase label asks that malposition, mechanical failure, suture constriction and precipitates be considered first, and warns against vigorous suction or excessive pressure, which can damage the catheter or push a clot into the circulation. If thrombosis of the vein is suspected (swelling, pain), ESMO recommends Doppler ultrasound [III, A].

For a suspected clot in the lumen, alteplase 2 mg in 2 ml (for people of 30 kg or more) is instilled and left; function is checked at 30 minutes and again at 120 minutes, and a second dose may be given if function has not returned at 120 minutes. In the label's trials, 75% of 995 patients had function restored 120 minutes after the first dose and 85% overall after up to two doses. Once restored, 4 to 5 ml of blood is aspirated to remove the drug and clot before a saline flush. The Cochrane review (2012) found low-quality evidence that urokinase restores patency better than placebo (RR 2.09; number needed to treat 4) and very low-quality evidence for alteplase, and could not judge safety. Regular saline flushing after every use is the main prevention (ESMO [II, B]).

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: blocked PICC; blocked port; CVAD occlusion; line will not bleed back; withdrawal occlusion; Cathflo; alteplase line lock; urokinase lock; persistent withdrawal occlusion

## Connected records

- protocols: [Catheter-related thrombosis in people with cancer: diagnosis, anticoagulation and whether the line can stay](https://onco.cc/protocols/catheter-related-thrombosis-in-cancer/), [Central line and port care in the community and at home](https://onco.cc/protocols/community-care-of-vascular-access-devices/), [Implanted port access, flushing and care in adults having cancer treatment](https://onco.cc/protocols/implanted-port-access-and-care/), [PICC and tunnelled central line care: dressing, hub cleaning, flushing and living with the line](https://onco.cc/protocols/picc-and-tunnelled-line-care/)
- technologies: [Catheter lock solutions (heparin, taurolidine and DefenCath)](https://onco.cc/technologies/catheter-lock-solutions/), [Implanted ports for chemotherapy (port-a-cath, power-injectable, apheresis and intraperitoneal ports)](https://onco.cc/technologies/implanted-ports/), [Non-coring (Huber) needles for port access](https://onco.cc/technologies/huber-needles-port-access/), [Peripherally inserted central catheters (PICC lines)](https://onco.cc/technologies/picc-lines/)
- terms: [Central venous access (port, PICC line)](https://onco.cc/terms/central-venous-access/), [Venous thromboembolism (VTE)](https://onco.cc/terms/vte/)

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