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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.
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]).
Why: Many blocked lines are not clotted, and a clot-dissolving drug will not fix a kink or a misplaced needle.
“Several mechanical causes can lead to a blockage: kink in catheter, tight suture, huber needle dislodge or occlusion, the catheter tip being blocked by the vessel wall and pinch-off syndrome (compression of the catheter, caused by its passage through the narrow angle between the first rib and the lateral portion of the clavicle).”
Why: Precipitates need a different solution from clots.
“Inappropriate concentration or inadequate mixture can cause the precipitation of medications in the catheter lumen (low or high pH, calcium phosphate precipitate, lipid emulsion, high-osmolarity and high-protein nutrition formulas) [ 109 ].”
Why: Force can split the catheter or push a clot into the lungs.
“Because of the risk of damage to the vascular wall or collapse of soft‑walled catheters, vigorous suction should not be applied during attempts to determine catheter occlusion.”
Why: A clot in the vein around the catheter needs anticoagulant treatment, not just clearing of the line.
“Although venography is considered the gold standard for the diagnosis of CRT, Doppler ultrasound is usually carried out [III, A]”
ESMO (Annals of Oncology) 2015 · [III, A]
Why: A small dose left in the catheter dissolves the clot in most cases.
“Patients weighing ≥30 kg: 2 mg in 2 mL”
Why: Most clots clear within two hours; a second dose clears some of the rest.
“If catheter function is not restored at 120 minutes after 1 dose of Cathflo Activase, a second dose may be instilled”
Why: The drug and the loosened clot should come out rather than be pushed into the bloodstream.
“If catheter function has been restored, aspirate 4–5 mL of blood in patients ≥10 kg or 3 mL in patients <10 kg to remove Cathflo Activase and residual clot, and gently irrigate the catheter with 0.9% Sodium Chloride Injection, USP”
Why: A line that still will not work after two doses is likely misplaced, damaged or sheathed, and further doses have not been studied.
Common practice: The alteplase label gives no safety or efficacy data beyond two 2 mg doses, and ESMO's comparison table lists removal of a non-functional catheter among the options in other guidelines; no guideline read sets out the imaging step.
Why: Leaving blood or drug in the catheter is the commonest cause of clotting and precipitate.
“Routine flushing with saline, after the completion of any infusion or blood sampling, is recommended [II, B]”
ESMO (Annals of Oncology) 2015 · [II, B]
How care is usually carried out, read from the guidelines and standards cited. Your own team's protocol and their judgement come first; this page is for understanding it, not for doing it yourself.
No graded oncology guideline sets out an occlusion algorithm that could be read. The best-supported sequence combines ESMO 2015 (rule out mechanical and precipitate causes; Doppler ultrasound for suspected thrombosis [III, A]; saline flushing after every use [II, B]) with the alteplase label (2 mg in 2 ml, check at 30 and 120 minutes, a second dose if needed, aspirate before flushing, no force). The evidence for thrombolytics is weak: the Cochrane review (2012) rated urokinase low quality and alteplase very low quality for efficacy, and could not judge safety.
ESMO (Annals of Oncology) 2015 · US National Library of Medicine, DailyMed (Genentech) 2026 · Cochrane Database of Systematic Reviews (van Miert et al.) 2012
Where it differs: Uses urokinase as the catheter thrombolytic, as some countries do where alteplase for catheters is not licensed.
Evidence: Cochrane 2012: low-quality evidence from two studies that urokinase restores patency better than placebo (RR 2.09, 95% CI 1.47 to 2.95; number needed to treat 4), with insufficient evidence on safety. Doses vary by product and country and were not read from a label here.
Cochrane Database of Systematic Reviews (van Miert et al.) 2012
| Recommendation | Grade, as printed | Source |
|---|---|---|
| Urokinase more effective than placebo for restoring patency “There was low quality evidence from a meta-analysis of two studies suggesting that urokinase (various strengths) was more effective than placebo for restoring patency to occluded CVC lumens in adults and children with underlying medical conditions (relative risk (RR) 2.09, 95% confidence interval (CI) 1.47 to 2.95), with a number needed to treat of 4 (95% CI 2 to 8).” | Low-quality evidence | Cochrane Database of Systematic Reviews (van Miert et al.) 2012 |
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