Pediatric Clinics of North America - CIPERJ

312 GOLDENBERG & BERNARD
Table 3
Recommended intensities and durations of conventional antithrombotic therapies in children,
by etiology and treatment agent
Agents and target anticoagulant activities
Duration of therapy, by
Episode Initial treatment Extended treatment etiology
First UFH 0.3–0.7 anti-Xa
U/mL
Warfarin INR 2.0–3.0 Resolved risk factor: 3–6
months
LMWH 0.5–1.0
anti-Xa U/mL
LMWH 0.5–1.0
anti-Xa U/mL
No known clinical risk
factor: 6–12 months
Chronic clinical risk factor:
12 months
Potent congenital
thrombophilia: indefinite
Recurrent UFH 0.3–0.7
anti-Xa U/mL
Warfarin INR 2.0–3.0 Resolved risk factor: 6–12
months
LMWH 0.5–1.0
anti-Xa U/mL
LMWH 0.5–1.0
anti-Xa U/mL
No known clinical risk
factor: 12 months
Chronic clinical risk factor:
indefinite
Potent congenital
thrombophilia: indefinite
of anticoagulant efficacy, and a decreased risk for the development of heparin-induced
thrombocytopenia (HIT). UFH (which has a shorter half-life
than LMWH) typically is preferred in circumstances of heightened bleeding
risk or labile acute clinical status, given the rapid extinction of anticoagulant
effect after cessation of the drug. In addition, UFH often is used for acute
VTE therapy in the setting of significant impairment or lability in renal function
because of the relatively greater renal elimination of LMWH. Common
initial maintenance dosing for UFH in non-neonatal children begins with an
intravenous loading dose (50 to 75 U/kg) followed by a continuous intravenous
infusion (15 to 25 U/kg per hour). In full-term neonates, a maintenance
dose (up to 50 U/kg per hour) may be required, especially if the clinical condition
is complicated by antithrombin consumption. The starting dose for
the LMWH enoxaparin in non-neonatal children commonly ranges between
1.0 and 1.25 mg/kg subcutaneously on an every-12-hour schedule; no bolus
dose is given. In full-term neonates, a higher dose of enoxaparin (1.5 mg/kg)
typically is necessary [15]. Some recent research has investigated whether
once-daily enoxaparin dosing may be suitable for acute VTE therapy
in children. For the LMWH dalteparin, initial maintenance dosing of
100–150 antifactor Xa (anti-Xa) U/kg seems appropriate based on available
pediatric data [16]; however, further studies are warranted (with more robust
representation of all age groups within the pediatric age range) to determine
the optimal intensity and frequency of dosing of dalteparin.
Heparin therapy, UFH or LMWH, is monitored most accurately by anti-
Xa activity. Anti-Xa level is obtained 6 to 8 hours after initiation of UFH