Pediatric Clinics of North America - CIPERJ

CARE OF PATIENTS WITH VASCULAR ANOMALIES
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(see the article by Goldenberg and Bernard elsewhere in this issue for more
details). Among these are antithrombin and protein C and S deficiency, factor
V Leiden mutation, C677T MTHFR gene mutation, PAI-1 4G/G polymorphism,
hyperhomocysteinemia, antiphospholipid antibodies, lupus
anticoagulant, and G20210A prothrombin gene mutation [55,56]. There are
other situations in which endothelial abnormalities increase the risk for
thrombosis, such as sickle cell disease and malignancy [57,58]. In adults, genetic
alterations interact with other risk factors, such as the use of oral contraceptives,
trauma, immobilization, and surgical procedures, to increase the
thrombotic risk for patients. The overall risk in the presence of multiple risk
factors can exceed the sum of the separate effects. There is no information
about the prevalence of thrombophilic predispositions in patients who have
vascular anomalies. It is presumed that patients who have a genetic predisposition
toward thrombophilia have an increased risk for thrombosis and coagulopathy
if they also have an extensive slow flow vascular malformation, but
studies of thrombophilia and vascular anomalies are not published to date.
Management
All patients who have extensive VM, VLM, or CVLM should have a baseline
hematologic evaluation. The authors recommend that baseline testing
include a complete blood count, prothrombin time, activated partial thromboplastin
time, fibrinogen, D-dimer, and prothrombotic assessment (ie, proteins
C and S, prothrombin gene mutation, thrombin-antithrombin, factor
V Leiden, PAI-1 polymorphism, factor VIII, homocysteine level, lupus anticoagulant,
anticardiolipin antibody, and antithrombin III). Patients found
to have abnormalities in their initial blood work should have a formal hematology
consultation before any surgical or interventional procedure and
before or during pregnancy. Those patients at high risk for thrombotic complications
should receive LMWH (enoxaparin-LMWH) at 0.5 mg/kg/dose
(maximum 60 mg/dose) once or twice a day (adults 30 mg twice daily) for
at least 2 weeks before any surgical or invasive radiologic procedure.
LWMH should be stopped 12 hours before the procedure and restarted
12 hours after the procedure. Anticoagulant dosing during pregnancy may
vary and should be determined and monitored by a hematologist and obstetrician
specializing in maternal fetal medicine.
LMWH also can be used daily to alleviate pain caused by inflammation,
thrombosis, and formation of phleboliths in patients who have high-risk
vascular malformations. Although no prospective studies are available,
clinical experience has demonstrated its effectiveness in this setting. While
patients are on LMWH, anti-factor Xa levels should be monitored. They
normally are drawn 4 to 6 hours after the subcutaneous administration of
LMWH. The target anti–factor Xa level should be less than 0.5 units/mL
for prophylaxis. A complete blood count and liver function testing
should be checked every 4 to 6 months with long-term LMWH dosing.