Flushing and Maintenance of Central Venous Access Devices

General Recommendations

Sterile 0.9% sodium chloride (normal saline) should be used to flush and lock catheter lumens that are in frequent use, with Grade A evidence supporting this practice 1, 2
For catheters accessed frequently or closed for short periods (<8 hours), normal saline flushing alone is sufficient to maintain patency 1
Three different meta-analyses have concluded that intermittent flushing with heparin is no more beneficial than flushing with normal saline alone for most central venous access devices 1

Heparinized solutions should be used as a lock (after proper flushing with saline) in specific situations, including when recommended by the manufacturer, for implanted ports that will remain closed for more than 8 hours, and for open-ended catheter lumens scheduled to remain closed for more than 8 hours 1
For intermittently accessed devices, flushing with 5-10 U/mL heparinized saline 1-2 times weekly can help maintain patency 3

When heparin is indicated, most authors suggest using a concentration between 50 and 500 units per mL, with Grade C evidence supporting this range 1
For devices that remain unused for prolonged periods, small caliber devices (5 Fr or less) should be flushed weekly, and large caliber devices (6 Fr or more) should be flushed every 3-4 weeks 1

Close-ended valve catheters should be flushed and locked with saline only, following manufacturer's instructions 1
Heparin should not be used immediately before or after administration of lipid-containing parenteral nutrition admixtures, as heparin may facilitate lipid precipitation 1
If heparin must be used after lipid administration, a saline flush should always be interposed between the lipid infusion and heparin, with Grade B evidence supporting this practice 1

The American Society for Parenteral and Enteral Nutrition recommends using normal saline for routine flushing and locking of port-a-caths, as it has been shown to be equivalent to heparin in maintaining patency with better safety 4
Normal saline is non-inferior to heparin for preventing catheter occlusion, reflux dysfunction, and flow dysfunction, according to a retrospective study, prospective randomized trial, and two systematic reviews 4

The European Society for Clinical Nutrition and Metabolism (ESPEN) guidelines explicitly recommend against routine heparin lock for home parenteral nutrition catheters, stating saline should be the standard, with a Grade B recommendation and 95.5% agreement 4
Heparin promotes intraluminal biofilm formation, potentially increasing catheter-related bloodstream infection risk, and should be avoided in specific clinical contexts, such as before or after lipid-containing parenteral nutrition 4

The German guidelines give a Grade B recommendation against heparin use, and suggest using normal saline for catheter lumens in frequent use, with low concentrations of heparin (5-10 U/mL) if truly indicated 4
Maintaining strict aseptic technique during all port access regardless of flush solution is crucial, as recommended by the Clinical Nutrition guidelines 4

The American College of Radiology recommends using 100 U/mL heparin concentration as the standard for implantable ports when locked for periods >8 hours, with a volume equal to the internal catheter volume (typically 1-3 mL depending on catheter size) 5
A large adult study found no differences in port malfunction or sepsis between saline versus 100 U/mL heparin flushes, supporting the use of saline over heparin 6

Multiple meta-analyses demonstrate no benefit of heparin over saline for maintaining port patency, although the specific meta-analyses are not cited here 6
A 2022 randomized trial demonstrated that saline locks every 2 months showed no differences in safety, infection, or thrombosis compared to heparin, however this trial is not directly cited here but is mentioned as part of the evidence base 6

In pediatric patients, a total of 200–300 U of heparin per flush is commonly employed for implanted ports. [7][8]
For infants weighing less than 10 kg, the typical dose is 10 U of heparin per kilogram of body weight per flush. [7][8]
In pediatric oncology patients with implantable ports, comparative studies showed no difference in complication rates between using 100 U/mL versus 10 U/mL heparin solutions for flushing. 8

Systemic exposure to heparin can lead to thrombocytopenia, bleeding, allergic reactions, and osteoporosis. 7
In premature newborns, heparin use is associated with a higher risk of intraventricular hemorrhage. 7
When heparin is combined with calcium‑containing lipid emulsions, it may destabilize the emulsion and cause coalescence of fat droplets, potentially leading to lipid emboli; this effect is unlikely at very low concentrations (≈0.5–1.0 U/mL). 7

A Cochrane systematic review found no convincing difference in maintaining central venous catheter (CVC) patency when comparing heparin flushes to normal saline flushes. 8

For ports that are not in use, a recommended maintenance schedule is to flush the device every 8 weeks to preserve patency. 8