Thrombotic Disorders

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Pediatric Clots - Tiny Troubles

  • Definition: Pathological formation of blood clots (thrombi) in arteries or veins in children, obstructing blood flow.
  • Pediatric vs. Adult Differences:
    • Lower incidence in children.
    • Different risk factor profiles (e.g., congenital heart disease, central lines more prominent in peds).
    • Developmental hemostasis: different levels of coagulation factors.
  • Virchow's Triad (Pediatric Context): 📌 SHE
    • Stasis: Immobility, congenital heart disease (CHD) with shunts, Fontan circulation.
    • Hypercoagulability: Sepsis, inherited thrombophilias (e.g., Factor V Leiden, Protein C/S deficiency), nephrotic syndrome, malignancy, certain medications (e.g., L-asparaginase).
    • Endothelial Injury: Central venous lines (CVL), trauma, surgery, vasculitis.

⭐ Central venous lines are a leading risk factor for VTE in hospitalized children.

Virchow's Triad in Pediatric Patient with Central Line

Clot Catalysts - Why Kids Clot

Pediatric thrombosis often results from an interplay between underlying genetic predispositions and various acquired conditions that promote clot formation.

Inherited Thrombophilias: These are genetic defects increasing thrombosis risk.

ConditionMechanism / Note
Factor V LeidenActivated Protein C (APC) resistance
Prothrombin G20210A↑ Prothrombin synthesis
Protein C DeficiencyImpaired inactivation of FVa & FVIIIa
Protein S DeficiencyReduced Protein C cofactor activity
Antithrombin (AT) DeficiencyReduced inhibition of thrombin & FXa

Acquired Risk Factors:

  • Central Venous Lines (CVL): Most common.
  • Sepsis: Systemic inflammation.
  • Malignancy: e.g., ALL; L-asparaginase.
  • Surgery / Trauma.
  • Nephrotic Syndrome: Loses anticoagulants (AT, Protein C/S).
  • Antiphospholipid Syndrome (APS).
  • Kawasaki Disease: Vasculitis, aneurysms.
  • Immobility / Dehydration.

Clot Confirmation - Spotting the Signs

Clinical Presentation (Site-Dependent):

  • DVT: Limb swelling, pain, warmth. Neonates: discoloration, edema.
  • PE: Sudden dyspnea, chest pain, hypoxia.
  • CSVT: Headache, seizures, focal deficits. Neonates: lethargy.
  • Arterial: 5 Ps (Pain, Pallor, Pulselessness, Paresthesia, Paralysis); organ ischemia.
  • Renal Vein (RVT): Flank mass, hematuria, thrombocytopenia (esp. neonates).

Diagnostic Workup:

  • Labs:
    • D-dimer: ↑ (High NPV).
    • Coagulation Profile: PT, aPTT, Fibrinogen.
    • Specific Assays (recurrent/unprovoked): Protein C/S, AT, FVL, Prothrombin G20210A (Timing: ~4-6 weeks post-event, off anticoagulants).
  • Imaging:
    • DVT: Doppler US.

      ⭐ Doppler ultrasound is the initial imaging of choice for suspected DVT.

    • PE: CT Pulmonary Angiography (CTPA); V/Q scan.
    • CSVT: MR Venography (MRV) / CT Venography (CTV).
    • Arterial: Doppler US, CTA/MRA.

Pulmonary Embolism CT Angiography

Clot Combat - Treatment Tactics

  • Core Strategy: Anticoagulation to halt clot growth & prevent recurrence.
    AgentKey FeaturesMonitoring
    LMWHEnoxaparin: 1mg/kg BD (>2mo), 1.5mg/kg BD (<2mo). SC.Anti-Xa levels
    UFHIV infusion. Rapid onset/offset.aPTT
    WarfarinOral. Target INR 2-3. Bridging needed.INR
    DOACsDabigatran, Rivaroxaban. Oral. Fixed doses. Growing pediatric use.Minimal/Specific
  • Thrombolysis (tPA): For severe, life/limb-threatening clots. High bleeding risk.
  • Prophylaxis: Crucial for high-risk (central lines, surgery, inherited thrombophilia).
  • Special Scenarios:
    • Neonatal Thrombosis: Often catheter-related. LMWH is first-line.
    • Purpura Fulminans: Urgent anticoagulation (LMWH/UFH), FFP, Protein C.

⭐ LMWH is generally preferred for anticoagulation in children due to predictable pharmacokinetics and subcutaneous administration.

Pediatric Anticoagulation Therapy Decision Tree

High‑Yield Points - ⚡ Biggest Takeaways

  • Factor V Leiden is the most common inherited thrombophilia; central venous lines are a key acquired risk.
  • Neonatal thrombosis is often linked to umbilical catheters or maternal conditions like Antiphospholipid Syndrome (APS).
  • Severe Protein C or S deficiency can present as neonatal purpura fulminans.
  • Kawasaki disease poses a risk for coronary artery thrombosis from aneurysms.
  • Low Molecular Weight Heparin (LMWH) is the preferred initial anticoagulant in most pediatric thrombotic events.
  • Nephrotic syndrome is a significant acquired risk factor due to urinary loss of anticoagulant proteins.
  • Always investigate for underlying malignancy or sepsis in unexplained pediatric thrombosis.

Practice Questions: Thrombotic Disorders

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Hb _____ levels are increased in juvenile chronic myeloid leukemia (JMML)

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