(b) Check complete blood count, platelet

count, activated partial thromboplastin time

(aPTT), prothrombin time and fibrinogen

levels before starting UFH therapy.

(c) Dosage: Is adjusted according to gestational

age (12).

<28 weeks GA: Loading dose 25 U/kg IV

over 10 minutes

Maintenance dose 15 U/kg/h

28 to 37 weeks GA: Loading dose 50 U/kg

IV over 10 minutes

Maintenance dose 15 U/kg/h

>37 weeks GA: Loading dose 100 U/kg IV

over 10 minutes

Maintenance dose 28 U/kg/h

(d) Monitoring

i. Maintain anti–factor Xa (anti-FXa) level of

0.03 to 0.7 U/mL (aPTT 60 to 85 seconds)

ii. Check anti-FXa level 4 hours after loading dose and 4 hours after every change

in the infusion rate.

iii. Check platelet counts and fibrinogen

levels daily for 2 to 3 days once therapeutic levels are achieved and at least

twice weekly thereafter, while on UFH.

iv. Monitor thrombus closely both during

and following treatment.

(e) Complications

i. Bleeding: Discontinue UFH infusion;

consider protamine sulphate if anti-FXa

level is >0.8 U/mL and there is active

bleeding. Dosage: 1 mg/ 100 U heparin

received if the time since the last heparin dose is <30 minutes. Use protamine

conservatively, starting with a smaller

dose than calculated.

ii. Heparin-induced thrombocytopenia (rare

in neonates) (15)

(2) LMWH (16,17)

(a) LMWHs have specific activity against factor

Xa and less activity against thrombin, so

therapy is monitored by anti-FXa assay and

not by aPTT.

(b) Different LMWHs preparations (e.g.,

enoxaparin, dalteparin, reviparin) differ in

their molecular weights and dosage regimens. Enoxaparin is the LMWH most commonly used.

(c) Advantages: Subcutaneous administration

(d) Dosage: Administered either by subcutaneous injection or through an indwelling subcutaneous catheter (Insuflon, Unomedical,

Birkerod, Denmark)

Term neonates: 1.7 mg/kg every 12 hours.

Preterm neonates: 2 mg/kg every 12 hours.

(e) Monitoring

i. Adjust dose to maintain anti-FXa level

between 0.5 and 1 U/mL.

ii. In neonates, prematurity, rapid growth,

and liver and kidney dysfunction make

LMWH dosage less predictable.

Frequent adjustment of the dose is

required to attain target anti-FXa levels.

iii. Draw blood sample for testing from

fresh venipuncture. There must be no

contamination from standard heparin

(e.g., from an arterial line).

iv. Check levels 4 hours after subcutaneous

administration of LMWH on days 1 and

2 of treatment.

v. If therapeutic, a weekly check of antiFXa levels is adequate.

(f) To discontinue anticoagulation, simply discontinue LMWH therapy. If an invasive