The incidence of thromboembolic events (
TEs) in childhood is greatly underestimated. Two age groups account for approximately 70% of
TEs in childhood: infants and teenagers. There are several predisposing risk factors for newborns such as small vessels, high hematocrit, and a unique neonatal
hemostatic system. Central venous lines contribute to 80% of
deep vein thrombosis in newborns. Other risk factors for all children are
shock syndromes, trauma, surgery, heart and
kidney disease, and acquired or hereditary
thrombophilias. The best prophylaxis is to recognize, avoid, and remove risk factors if possible. This is particularly relevant in childhood, where risk factors can be found in the majority of
TEs. The serious sequelae of
TEs (mortality, and short- and long-term morbidity) require therapeutic intervention.
Unfractionated heparin (UFH) has the following disadvantages: age-dependent unpredictable pharmacokinetics, the need for intravenous access for
therapy and monitoring, delays in achieving therapeutic ranges,
bleeding risk, the risk of
heparin-induced
thrombocytopenia, and
osteoporosis with long-term use. Oral
anticoagulants, in addition to some of these disadvantages, show considerable variation by diet (especially if there is a change from breast to
bottle feeding), medication, and intercurrent illness. Review of case reports and cohort studies on 728 children treated with
low-molecular-weight heparin (
LMWH) indicate the following advantages over UFH: minimal monitoring, ease of administration (subcutaneous), and possibly equivalent efficacy and safety. Dose recommendations for pediatric patients cannot be directly extrapolated from those for adult patients. If dosages are calculated according to
body weight, infants < 3 months (or < 5 kg) need approximately 50% more
LMWH than older children or adults to reach prophylactic or therapeutic anti-
factor Xa levels. Further studies are necessary to address the following: the importance of risk factors, the necessity of screening for
hereditary thrombophilia, the efficacy and safety of treatment, and side effects and
duration of treatment. Thromboembolic events (
TEs) are considered to be rare in children. However, recent surveys reveal that
TEs in children occur more often than suspected. The incidence is greatly underestimated because
TEs are usually overlooked. Retrospective surveys in children treated for
acute lymphoblastic leukemia with
corticosteroids and
asparaginase revealed clinically symptomatic TE in only 2 to 12% of patients. However, in prospective studies with routine imaging, the incidence was more than 20%. The objectives of this article are to update the present knowledge on
TEs in children, including incidence, predominant age groups, risk factors, diagnosis, and indications for prophylaxis and
therapy; and to discuss the use of
low-molecular-weight heparin (
LMWH) in children.