Heparin Use with Arterial Lines
Heparin is not necessary for maintaining arterial line patency, as normal saline flush is equally effective and avoids the risks of heparin-related complications.
Evidence for Saline vs. Heparinized Flush
The most direct evidence addressing arterial line maintenance demonstrates no functional benefit of heparin:
- A randomized trial of 65 ICU patients compared normal saline flush (3 mL/hour) versus heparinized saline flush (1 unit/mL at 3 mL/hour) for arterial line function 1
- Mean arterial line function scores were identical: 83% (normal saline) versus 82% (heparinized saline), with no statistical difference at 95% confidence interval 1
- Study duration averaged 5.8-6.6 days, demonstrating sustained patency without heparin 1
Recommended Approach
Use continuous normal saline flush at 3 mL/hour for arterial line maintenance 1. This approach:
- Maintains adequate arterial waveform quality for hemodynamic monitoring 1
- Preserves line patency for blood sampling 1
- Eliminates heparin-related drug interactions 1
- Avoids risk of heparin-induced thrombocytopenia (HIT) 2
When Systemic Anticoagulation is Indicated
If the patient requires therapeutic anticoagulation for other clinical indications (not for arterial line patency), follow weight-based protocols:
For Acute Arterial Thrombosis/Ischemia
Administer unfractionated heparin as 60 U/kg bolus (maximum 4000 U) followed by 12 U/kg/hour continuous infusion (maximum 1000 U/hour) 3, 4, 5
- Target aPTT of 1.5-2.0 times control (approximately 50-70 seconds) 3
- Check aPTT at 6 hours after bolus, then adjust per nomogram 3
- This corresponds to heparin level of 0.2-0.4 U/mL by protamine titration 3
For Endovascular/Arterial Procedures
During arterial procedures, a standardized 5000 U bolus is inadequate 6:
- Only 33% of patients achieved ACT ≥200 seconds with 5000 U bolus 6
- Only 6% reached ACT ≥250 seconds 6
- Use weight-based dosing: 70 U/kg bolus to achieve ACT 200-300 seconds 2
- For high-risk procedures (balloon occlusion, parent vessel occlusion), maintain ACT 300-350 seconds during procedure 2
Monitoring Protocol for Therapeutic Heparin
When systemic anticoagulation is required 4:
- Baseline: Measure aPTT, INR, platelet count before initiating therapy 4
- Continuous IV infusion: Check aPTT every 4 hours initially, then at appropriate intervals 4
- Intermittent IV dosing: Check aPTT before each injection 4
- Subcutaneous dosing: Optimal sampling 4-6 hours post-injection 4
- Monitor platelet counts daily to detect HIT 3
Critical Pitfalls to Avoid
Do Not Use Heparin "Just for the Line"
- Heparin flush provides no benefit over saline for arterial line patency 1
- Unnecessary heparin exposure increases bleeding risk and HIT risk 2
- HIT occurs in up to 5% of patients receiving unfractionated heparin, with higher rates post-orthopedic surgery 2
Do Not Use Fixed-Dose Heparin for Arterial Procedures
- Standardized 5000 U bolus results in inadequate anticoagulation in 67% of patients 6
- Individual patient response to heparin shows large variability 6
- Always use weight-based dosing and ACT monitoring during arterial interventions 2, 6
Do Not Underdose Therapeutic Heparin
- Subtherapeutic aPTT (<1.5 times control) is associated with 25% risk of recurrent thromboembolism 7
- Failure to achieve therapeutic anticoagulation within first 24 hours significantly increases thrombotic complications 7
Avoid Intramuscular Administration
- Never give heparin intramuscularly due to frequent hematoma formation 4
- Use deep subcutaneous injection (above iliac crest or abdominal fat layer) if subcutaneous route needed 4
Special Populations
Renal Insufficiency
- Unfractionated heparin is preferred over LMWH when creatinine clearance <30 mL/min 8
- Heparin metabolism is primarily hepatic, requiring no renal dose adjustment 8