Troubleshooting a Blocked Chemoport
When encountering a blocked chemoport, first attempt to restore patency using normal saline flush with gentle pressure, followed by alteplase if unsuccessful, with a maximum of two doses of alteplase (2mg/2mL) instilled into the catheter with appropriate dwell times. 1, 2
Initial Assessment and Basic Troubleshooting Steps
- Before attempting to unblock the chemoport, ensure both limbs of the catheter are clamped and place a clean or sterile pad/towel under the catheter 1
- Perform hand hygiene and prepare supplies, maintaining sterility throughout the procedure 1
- Check for external causes of resistance such as kinks in the catheter limb or patient position that might be contributing to the blockage 1
- Clean the hub with chlorhexidine (or povidone if chlorhexidine not tolerated) using the "scrub the hub" technique 1
First-Line Intervention
- Attempt to aspirate 2-5 mL of blood and any locking solution from the lumen 1
- If resistance is felt or no blood return is obtained, try a gentle back-and-forth motion (irrigation technique) to promote catheter patency 1
- Flush with 10 mL of normal saline using a turbulent flushing technique to help clear any fibrin buildup in the catheter lumen 1
- Apply gentle pressure during flushing but avoid excessive force that could rupture the catheter 1
Second-Line Intervention (Thrombolytic Therapy)
If saline flushing is unsuccessful, proceed with thrombolytic therapy using alteplase:
- Reconstitute alteplase to a final concentration of 1 mg/mL by aseptically withdrawing 2.2 mL of Sterile Water for Injection and injecting it into the alteplase vial 2
- For adult patients (≥30 kg): Instill 2 mg in 2 mL of alteplase into the occluded catheter 2
- For pediatric patients (<30 kg): Use 110% of the estimated internal lumen volume, not to exceed 2 mg in 2 mL 2
- Allow a dwell time of 30 minutes, then assess catheter function by attempting to aspirate blood 2
- If the catheter remains non-functional, reassess after 120 minutes of total dwell time 2
- If function is still not restored after the first dose, a second dose of equal amount may be instilled following the same procedure 2
Post-Patency Restoration Care
- Once catheter function is restored, aspirate 4-5 mL of blood (3 mL in patients <10 kg) to remove the thrombolytic agent and any residual clot 2
- Gently irrigate the catheter with 0.9% sodium chloride 2
- Apply a new sterile cap to the port 1
- Document the intervention, including the agent used, dwell time, and outcome 1
Maintenance to Prevent Future Blockages
- For subcutaneous ports not in active use, perform a flush every four weeks with normal saline to maintain patency 1
- For tunneled cuffed catheters and PICC lines, a weekly flush is recommended 1
- Consider using heparinized saline for maintenance in patients with recurrent blockages, as some evidence suggests it may be more effective than normal saline alone 3
When to Seek Additional Intervention
- If catheter function cannot be restored after two doses of alteplase, radiological assessment should be considered to evaluate for mechanical occlusion, catheter malposition, or thrombosis 1
- Persistent blockage may require catheter replacement, especially if there are signs of infection or thrombosis 1, 4
- For patients with recurrent blockages, consider evaluation for underlying thrombotic conditions 1
Common Pitfalls and Caveats
- Never use excessive force when attempting to clear a blocked port as this may lead to catheter rupture or embolization 5
- Avoid using syringes smaller than 5 mL as they generate higher pressure that could damage the catheter 1
- Do not mix medications with thrombolytic agents during the unblocking procedure 2
- Be vigilant for signs of catheter-related infection during troubleshooting procedures, as manipulation increases infection risk 1
- Clinical trials show that up to 85% of occluded catheters can be successfully cleared with up to two doses of alteplase, so persistence with the protocol is warranted 2