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Initiation, Maintenance and Duration of Therapy

This guideline is not intended for patients on ECMO, cardiac bypass pump, hemodialysis or continuous renal replacement therapy. Refer to specific guideline for these situations.

Initiation of therapy

  • Obtain blood for CBC, PT, aPTT.

  • Loading heparin dose: 75-100 units/kg IV over 10 minutes.

    • Loading dose may not be indicated in certain clinical situations with increased bleeding risk.

  • Calculate initial maintenance heparin dose based on age and weight.

Initial maintenance dose:
 ≤ 1 year 28 units/kg/hour IV
> 1 year 20 units/kg/hour IV

  • Obtain blood for aPTT and/or heparin level 4 to 6 hours after administration of the loading dose (no earlier).

  • Adjust heparin to maintain the aPTT at 60-85 sec (or an aPTT which usually correlates to a heparin level of 0.35 to 0.7) using Table 1.

  • Obtain blood for aPTT and/or heparin level 4 to 6 hours after every change in infusion rate.

  • Use heparin level to calibrate aPTT levels. Obtain aPTT at least daily if using heparin levels to titrate dosing.

Table 1 - Heparin Adjustment



Hold infusion

Rate change

Repeat PTT

< 50




4 hours




↑ 10%

4 hours




No Change

24 hours





4 hours





4 hours

> 120




4 hours

Duration of therapy

The duration of heparin therapy is dependent upon the primary problem.

  • General recommendations:

    • May start warfarin as early as day 1 if long-term anticoagulation is planned.

    • UFH/enoxaparin should be discontinued no earlier than day 6 and after INR has reached goal range for 2 consecutive days.

    • May convert to LMW heparin/enoxaparin when clinical situation allows.


David, M., et al. Heparin and LMWH in Children. Thrombosis Interest Group of Canada. January 2007. Accessed 11/15/08.

Lexi-Drugs Online/Pediatric Lexi-Drugs Online, Enoxaparin,, Copyright © 1978-2008 Lexi-Comp, Inc, Hudson, OH 44236

Monagle P, Chan AKC, Goldenberg NA, Ichord RN, Journeycake JM, Nowak-Gottl U, Vesely SK. Antithrombotic therapy in neonates and children: antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. Chest 2012; 141: e737S –e801S.

Roach ES. Golomb MR. Adams R. Biller J. Daniels S. Deveber G. Ferriero D. Jones BV. Kirkham FJ. Scott RM. Smith ER. American Heart Association Stroke Council. Council on Cardiovascular Disease in the Young. Management of stroke in infants and children: a scientific statement from a Special Writing Group of the American Heart Association Stroke Council and the Council on Cardiovascular Disease in the Young. [Journal Article] Stroke. 39(9):2644-91, 2008 Sep.

These guidelines do not establish a standard of care to be followed in every case. It is recognized that each case is different and those individuals involved in providing health care are expected to use their judgment in determining what is in the best interests of the patient based on the circumstances existing at the time. It is impossible to anticipate all possible situations that may exist and to prepare guidelines for each. Accordingly these guidelines should guide care with the understanding that departures from them may be required at times.