Heparinised Saline for Flushing Central Lines
For central venous catheters in frequent use (accessed daily), flush and lock with normal saline only—heparin provides no additional benefit and adds unnecessary risk. 1
Protocol Based on Catheter Access Frequency
Daily or Frequent Use (< 8 hours between access)
- Flush with 0.9% normal saline only (10 mL using turbulent flushing technique)
- No heparin required 1
- Grade A recommendation from ESPEN guidelines
- Multiple meta-analyses confirm heparin offers no advantage over saline for frequently accessed lines 1
Intermittent Access (> 8 hours between use)
For implanted ports and open-ended catheter lumens:
- First flush with saline (proper technique is critical)
- Then lock with heparinised saline: 5-10 U/mL concentration 2
- Frequency: 1-2 times weekly 2
- Volume: 3-5 mL sufficient for locking 1
- Grade C recommendation (based on manufacturer recommendations and clinical experience)
For closed-ended valve catheters:
- Flush and lock with saline only per manufacturer instructions 1
- No heparin needed regardless of access frequency
Critical Safety Considerations
Lipid-Containing Parenteral Nutrition
Never use heparin immediately before or after lipid infusions—heparin facilitates lipid precipitation. Always interpose a saline flush. 1
Pediatric Populations
- Daily use CVCs: Routine heparin NOT recommended over saline (conditional recommendation against) 2
- Intermittent access: 5-10 U/mL heparinised saline 1-2 weekly can be used (conditional recommendation for) 2
- Newborn PICCs: Evidence insufficient to recommend routine heparin despite some efficacy data—potential risks undefined 2
Hemodialysis Catheters
Follow specific protocols for catheter locking between dialysis sessions—typically involves aspiration of 2-5 mL blood/lock solution, then instillation of fresh locking solution per unit protocol 3
Evidence Quality and Rationale
The 2018 ESPGHAN/ESPEN pediatric guidelines 2 and 2009 ESPEN adult guidelines 1 provide the strongest evidence base. Three separate meta-analyses of randomized controlled trials concluded that intermittent heparin flushing is no more beneficial than normal saline alone for catheter patency. 1
Recent research supports these guidelines: A 2012 randomized trial of 709 catheter lumens found no significant difference in nonpatency rates between heparin (3.8%) and saline (6.3%) groups (RR 1.66,95% CI 0.86-3.22, p=0.136) 4. A 2015 study similarly found no difference in flushing ability or blood return between groups 5.
Common Pitfalls to Avoid
- Using heparin for daily-use catheters: Adds cost, complexity, and bleeding risk without benefit
- Inadequate saline flushing before heparinisation: Proper saline flushing technique is more important than heparin concentration 1
- Wrong heparin concentration: If using heparin, 5-10 U/mL is sufficient for intermittent access; higher concentrations (50-500 U/mL) lack evidence base 1
- Confusing therapeutic heparin vials with flush solutions: Fatal medication errors have occurred 6
- Heparin with lipid infusions: Risk of precipitation and catheter occlusion
Practical Algorithm
Is the catheter accessed daily or continuously?
- YES → Saline flush only (10 mL, turbulent technique)
- NO → Proceed to next question
Is it an implanted port or open-ended lumen closed > 8 hours?
- YES → Saline flush first, then heparinised saline lock (5-10 U/mL) weekly
- NO → Check if closed-ended valve catheter
Closed-ended valve catheter?
- YES → Saline only per manufacturer
- NO → Follow manufacturer recommendations
Recent lipid infusion?
- YES → Mandatory saline flush before any heparin