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Anticoagulant flush / catheter maintenance Pregnancy: Minimal systemic absorption; safe for line flushing.

Unfractionated Heparin (Peripheral/Central Line Flush)

Brand names: Heparin Sodium 10 units/mL, Heparin Sodium 100 units/mL

Adult dose

Dose: Peripheral IV: 10–50 units in 2–5 mL NaCl 0.9%; Central line: 50–100 units in 5 mL
Route: IV (catheter flush)
Frequency: After every use or every 8–12 hours if not in use
Max: Per institutional protocol
Peripheral cannula flush: 10 units/mL — 2–5 mL after each use. Central line flush: 100 units/mL — 5 mL after use. Arterial line maintenance: 1–5 units/mL in flush solution. Many institutions switching to 0.9% NaCl for peripheral cannulae (evidence comparable, no HIT risk).

Paediatric dose

Route: IV flush
Frequency: Per protocol
Max: Institutional protocol
Concentration: 10 units/ml
Neonates: use 0.5–1 unit/mL (ONLY if heparin flushes used — many neonatal units use saline only). Children: institutional protocol — typically 10 units/mL for peripheral, 100 units/mL for central. HIT risk rare but exists.

Dose adjustments

Renal

Not applicable for line flushing.

Hepatic

Not applicable for line flushing.

Clinical pearls

  • HIT can be triggered by even tiny heparin flush doses — if HIT diagnosed, use heparin-free flush (0.9% NaCl) and alternative anticoagulation
  • Many guidelines now recommend normal saline instead of heparin for peripheral cannulae (less HIT risk, equally effective)
  • Ensure correct concentration: never confuse 10 units/mL and 25,000 units/mL vials (this is a well-documented error)
  • Pre-filled flush syringes reduce medication errors

Contraindications

  • HIT (heparin-induced thrombocytopenia) — any heparin absolutely contraindicated

Side effects

  • HIT (rare but significant — even flush doses can trigger)
  • Local thrombosis with incorrect technique
  • Inadvertent systemic heparinisation with frequent large-volume flushes (neonates at risk)

Interactions

  • Heparin flushed into lines with other medications may cause incompatibility

Monitoring

  • Platelet count (if using heparin flushes regularly)
  • Line patency

Reference: BNFc; BNF; Infusion Nursing Standards; Intravenous Therapy Nursing Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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