What is the appropriate heparin dose and volume for flushing a tunneled or implanted venous port?

Heparin Port Flush Dosing

For implanted venous ports, use 100 U/mL heparin concentration in a volume equal to the internal catheter volume (typically 1-3 mL depending on catheter size) when the port will remain closed for more than 8 hours. 1

Evidence-Based Dosing Recommendations

Adult Implanted Ports

• Standard concentration: 100 U/mL heparin is recommended by the American College of Radiology for locking implanted ports when closed for periods >8 hours 1
• Volume: 1-3 mL depending on the internal catheter volume, which varies by device size 1
• A large adult study found no differences in port malfunction or sepsis between saline versus 100 U/mL heparin flushes, supporting that saline may be equally effective 1

Pediatric Populations

• Children: 200-300 U total heparin per flush is commonly used 2
• Infants <10 kg: 10 U/kg is the frequently employed dose 2
• For pediatric oncology patients with implantable ports, studies found no difference in complication rates between 100 U/mL versus 10 U/mL heparin solutions 2

When Heparin Should Actually Be Used

Critical distinction: Multiple meta-analyses demonstrate that heparin provides no additional benefit over normal saline for maintaining port patency 1, 3. The evidence challenges routine heparin use:

• Saline is preferred for ports accessed frequently or closed <8 hours 1, 3
• Heparin lock (after saline flush) is indicated only for ports remaining closed >8 hours, when manufacturer-recommended, or for open-ended catheter lumens 1, 3
• The European Society for Clinical Nutrition and Metabolism (ESPEN) explicitly recommends against routine heparin lock with Grade B recommendation and 95.5% agreement, stating saline should be the standard 1, 3

Important Safety Considerations and Pitfalls

Heparin-Related Risks

• Heparin promotes intraluminal biofilm formation, potentially increasing catheter-related bloodstream infection risk 1, 3
• Potential systemic effects include thrombocytopenia, bleeding, allergic reactions, and osteoporosis 2
• In premature newborns, there may be increased risk of intraventricular hemorrhage 2

Critical Contraindications

• Never use heparin immediately before or after lipid-containing parenteral nutrition, as heparin facilitates lipid precipitation 1, 3
• If heparin must be used after lipid administration, always interpose a saline flush between the lipid infusion and heparin 1
• Calcium and heparin can destabilize lipid emulsions, causing coalescence of fat droplets with lipid emboli, though this is unlikely at low concentrations (0.5-1.0 U/mL) 2

Alternative Approach: Saline-Only Protocol

Growing evidence supports saline-only flushing:

• A Cochrane review found no convincing difference in maintaining CVC patency between heparin and normal saline flushes 2, 4
• A systematic review of totally implanted venous access ports in cancer patients showed saline can safely replace 50 or 100 U/mL heparin 5
• Normal saline is non-inferior to heparin for preventing catheter occlusion, reflux dysfunction, and flow dysfunction 1

Saline Flushing Technique

• Use ≥10 mL syringes to prevent excessive pressure that could damage the catheter 3
• Employ turbulent push-pause technique to create turbulence that clears the catheter lumen 3
• Flush with volume at least twice the catheter volume 3

Practical Algorithm for Port Maintenance

For ports accessed frequently or closed <8 hours:

• Use normal saline flush only (10 mL) 1, 3

For ports remaining closed >8 hours:

• Flush with normal saline first (10 mL) 1
• Lock with 100 U/mL heparin, volume equal to internal catheter volume (1-3 mL) 1

For ports not in use for prolonged periods:

• Flush every 8 weeks if not in use 2
• Consider 5-10 U/mL heparinized saline 1-2 times weekly for intermittently accessed devices 1, 3