Can a midline catheter be flushed with heparin (anticoagulant) if needed?

Midline Catheter Flushing: Saline is Preferred Over Heparin

Midline catheters should be flushed with normal saline (0.9% sodium chloride) rather than heparin, as saline is equally effective for maintaining patency and avoids the risks associated with heparin use. 1

Primary Recommendation

• Sterile 0.9% sodium chloride (normal saline) should be the standard flush solution for midline catheters, with Grade A evidence supporting this practice for central venous access devices 1
• Multiple meta-analyses have concluded that intermittent flushing with heparin provides no additional benefit over normal saline alone for maintaining catheter patency 1
• For catheters accessed frequently or closed for short periods (<8 hours), normal saline flushing alone is sufficient 1

When Heparin May Be Considered (Rarely for Midlines)

While heparin is generally not recommended for midline catheters, there are specific circumstances where it might be used:

• Heparinized solutions (5-10 U/mL) may be considered only when specifically recommended by the manufacturer or for open-ended catheter lumens scheduled to remain closed for more than 8 hours 1
• If heparin is deemed necessary, use concentrations between 50-500 units per mL, though most authors suggest the lower end of this range 1
• For intermittently accessed devices remaining unused for prolonged periods, flushing with 5-10 U/mL heparinized saline 1-2 times weekly can be considered 1

Critical Safety Considerations and Pitfalls

Avoid heparin use due to significant risks:

• Heparin promotes intraluminal biofilm formation, potentially increasing catheter-related bloodstream infection risk 1
• Risks of heparin prophylaxis include thrombocytopenia and bone disease, which presumably outweigh the risk of thrombosis in many cases 2
• Heparin should never be used immediately before or after administration of lipid-containing parenteral nutrition, as heparin may facilitate lipid precipitation 1
• If heparin must be used after lipid administration, a saline flush must always be interposed between the lipid infusion and heparin 1

Evidence-Based Rationale

The recommendation against routine heparin use is supported by:

• A 2017 meta-analysis of 7,875 subjects demonstrated that normal saline is equally, if not more effective, in keeping central venous catheters open 3
• A 2012 randomized trial of 326 catheters showed nonpatency rates of 3.8% with heparin versus 6.3% with saline (not statistically significant, p=0.136), supporting saline as the preferred solution given heparin's safety concerns 4
• The European Society for Clinical Nutrition and Metabolism (ESPEN) explicitly recommends against routine heparin lock, stating saline should be the standard with Grade B recommendation and 95.5% agreement 1

Practical Flushing Protocol

For routine midline maintenance:

• Flush with normal saline using a volume at least twice the catheter volume 2
• Use 10 mL or larger syringes to prevent excessive pressure that could damage the catheter 5
• Employ turbulent push-pause technique when flushing to create turbulence that helps clear the catheter lumen 5
• Maintain strict aseptic technique during all catheter access 1

Management of Occlusion

If catheter occlusion occurs despite proper saline flushing:

• First attempt: forceful irrigation with saline, which will unclog the catheter in many cases 2
• If saline fails: use fibrinolytic drugs (urokinase or alteplase) for thrombotic occlusions with at least 30 minutes dwell time 2
• Non-thrombotic occlusions should be treated according to their etiology (lipid occlusion with 70% ethanol, mineral precipitates with 0.1 N HCl) 2