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Heparin - low dose therapy in children

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Standard Syringe

The standard low dose heparin mix is (500 x wt) units heparin diluted to 50ml with 5% glucose. Maximum weight for calculation is 50kg. If ≥50kg make up as for 50kg i.e. add 25,000 units.

1 ml/hr = 10 units/kg/hr


  • Infants <5kg with a central venous catheter (CVC)
  • All cardiac children with a single ventricle and a CVC
  • All cardiac children who have had a modified BT shunt, regardless of weight
  • "CVC heparin" must always be infused through the central venous catheter
  • Cardiac children <5kg who also receive aspirin continue their low dose heparin while they have a CVC
  • Do not stop low dose heparin for sternal closure

Low Dose Heparin delivery

  • Ensure a baseline APTT has been done
  • Normal APTT varies with age
    • < 1 month 31-55
    • > 1 month 25-37
  • No loading dose is given
  • Heparin is given as per the table below. Maximum dose is 500units/hr. There is no "goal" APTT.
  • Starting infusion:
    • in children who have had surgery, start 4 hours after ICU admission if there is no significant bleeding. Earlier if instructed to by surgeon.
    • Check the APTT and start heparin as per table.
  • Adjusting infusion:
    • APTT is checked 4 hours after infusion started and then 12 hourly if APTT within normal range for age.
    • If patient is bleeding stop heparin regardless of APTT.
Age < 1 month
APTT Heparin Infusion Rate (u/kg/hr) Notes
< 45 10  
45-55 5  
>55 0 Recheck in 4hrs
Age > 1 month
APTT Heparin Infusion Rate (u/kg/hr) Notes
< 35 10  
35-45 5  
>45 0 Recheck in 4hrs

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Document Control

  • Date last published: 26 November 2018
  • Document type: Clinical Guideline
  • Services responsible: Paediatric Intensive Care Unit
  • Owner: D Buckley
  • Editor: John Beca
  • Review frequency: 2 years