VTE in Children (bsh 2011, Addendum 2021)
intro
Annual incidence: 1 per 100,000 children
>90% 2o to medical/surgical risk factors
Bimodal age distribution: Neonates & adolescents
Diagnostic Imaging
DVT
Lower limb: USS and repeat after 1 week if first scan normal
Blocked line: CXR, linogram +/- MRV
Central Vein: Contrast MRV (alt: CT)
PE
VQ if CXR normal
CT if VQ non-diagnostic (alt: MRA)
Cerebral Venous Thrombosis
Urgent T2* MRI and MRV (alt: Pre- and Post- contrast CT)
Conventional angiography if MRI non-diagnostic
Laboratory Investigation
FBC, U&E and PT/APTT for safety of anticoagulation
Antiphospholipid antibodies if unprovoked —> long term AC if positive
Protein C and S only if purpura fulminans
Antithrombin only if early onset of spontaneous thrombotic events
Do not test D-dimer
Do not test heritable thrombophilias, consequence of a positive result not clear
Management
VTE
LMWH followed by warfarin (INR 2.5), DOAC or continuous LMWH
3 months if provoked
6 months if idiopathic
Long term if Antiphospholipid antibodies or recurrent VTE
Consider thrombolysis if extensive clot
Remove lines 2-4 days after start LMWH
IVC filter only if AC contraindicated
Cerebral Venous Thrombosis
LMWH / UFH / DOAC if small, or no, intracranial haemorrhage
3 months if provoked and trigger has resolved. Re-image at end of treatment
6 months if idiopathic. Re-image at end of treatment
Long-term if risk factors persist
No AC if haemorrhage is intraventricular or causing mass effect
If no AC —> re-image to look for clot extension
Prophylaxis
Physical prophylaxis in older children who are at risk of VTE
LMWH prophylaxis if multiple risk factors
No prophylaxis for lines, but avoiding siting in femoral or subclavian veins.
UFH Dosing
Loading – 75 iu/kg over 10 minutes
Then - <1 year olds 28 iu/kg/hr, >1 year olds 20 iu/kg/hour
Dalteparin Dosing
200 u/kg OD or 100 u/kg BD
50% larger dose if <8 weeks old or weight <5 kg (due to low antithrombin levels)
Prophylactic dose is half the treatment dose
Target Anti-Xa: 0.5-1.0 for treatment, 0.1-0.4 for prophylaxis
DOACs (BSH Addendum 2021)
Trials for Rivaroxaban (EINSTEIN-Jr) and Dabigatran (DIVERSITY) now published and found these two DOACs to be non-inferior to standard of care. Trials for Apixaban and Edoxaban ongoing. The guideline discusses the limitations in some detail but concludes:
Rivaroxaban and dabigatran should be offered for the treatment of VTE in people <18 years old
Five day’s parenteral anticoagulation should be given before starting the DOAC
Recommend warfarin for triple-positive APS, and suggest an alternative to DOAC for non-triple APS.