6.6 Consumptive Thrombocytopenias

Question 1

Your patient has thrombocytopenia. What is the platelet count?

What are associated symptoms?

What are the two broad categories of causes of this disorder, with specific types per cause?

Answer 1

• <150k
• Symptoms
  
  • Generalized fatigue
  • Mucocutaneous bleeding
  • Petechiae or purpura
  • Asymptomatic
• Two Broad Causes
  
  • Central
    
    • Bone marrow d/o
    • Congenital d/o
  • Peripheral
    
    • Bleeding
    • Immune destruction
    • Non immune destruction
    • Splenic sequestation

Question 2

Your patient has been bleeding from their gums and CBC shows a platelet count of 100k. What other labs will you consider getting?

Answer 2

• PT/INR
• Fibrinogen
• Factor V
• D dimer
• Fibrin split products
• Ferritin
• Triglycerides
• LDH
• Transaminases: AST/ALT
• Vit B12 and Folate

Question 3

Immune thrombocytopenia

• Definition
• Usual presentation
• Severe presentation
• Primary
• Secondary
• First line tx
• Second line tx
• Chronic ITP

Answer 3

• Definition
  
  • Immunologic destruction of platelets in response to an unknown aggressor
  • Severe < 20k, with NORMAL peripheral smear
• Usual presentation
  
  • Non urgent bleeding: bruising, petechiae, purpura, gingival bleed, epistaxis, hematuria, hematochezia, heavy menses
• Severe presentation
  
  • Severe, urgent bleeding: ICH, GI bleed, severe menorrhagia, frank hematuria
• Primary
  
  • 80%, Acquired immunologic destruction of platelets, no known inciting factor
  • Platelets destroyed by antibodies created against the platelet membrane antigens of GP IIb/IIIa and GP 1b/IX
  • Most often in spleen d/t macrophages
  • Impaired megakaryocytopoesis
  • T-cells can also destroy platelets in bone marrow
• Secondary
  
  • 20%, platelets destroyed by autoimmune cause due to other condition/disorder
  • Autoimmune disease
  • Viral and bacterial infection
  • Pharmaceuticals
• First line tx
  
  • If plt > 30k, with no significant bleeding: MONITOR
  • If < 30k or with bleeding
    
    • Plt transfusion
    • Long course of prednisone x 21 d with 6 wk taper
    • Or, high dose dex x4days
  • If severe bleeding
    
    • Give IVIG 1g/kg - temporizing measure
    • Give IV anti-D antibody
• Second line tx
  
  • Splenectomy
  • Rituximab
  • Thrombopoeietin receptor agonist
• Chronic ITP
  
  • Chemo, immunosuppressants, biologics

Question 4

Drug induced thrombocytopenia

• Cause
• Symptoms
• Treatment

Answer 4

• Cause
  
  • Meds/substances cause a form of immune mediated platelet destruction
• Symptoms
  
  • Hard to distinguish from ITP
  • Thorough history important
• Treatment
  
  • Stop offending agent > bleeding should stop within 1-2 d and plt should increase within 4-8d
  • If doesnt stop, not drug induced

Question 5

Heparin Induced Thrombocytopenia

• Non Immune
• Immune
• Typical platelet count
• Typical onset
• Delayed onset
• Rapid onset
• Clinical Probably scoring system
• Lab Testing
• Clinical Management
• HIT with Thromboembolism

Answer 5

• Non Immune
  
  • Mild drop in plt, w/in 4d of starting heparin
  • Not progressive, not thrombotic
• Immune
  
  • Follows prophylactic OR full heparin
  • Plt < 150k OR decrease 50% from baseline
  • Occurs 5-14d s/p heparin (usually)
• Typical platelet count
  
  • 38-60k
• Typical onset
  
  • 5-14d s/p exposure
• Delayed onset
  
  • 2-6wk s/p exposure
• Rapid onset
  
  • Hours to days (usually have had heparin in past 100d)
• Clinical Probably scoring system
  
  • 4 T’s of HIT
    
    • Thrombocytes
    • Timing of onset
    • Thrombosis
    • Thrombocytopenia cause
  • 0-2 pts per category
  • 0-3 total: low likelihood, cont heparin, search DDx
  • >4 total: High suspicion, D/C heparin, start non-hep AC, send HIT labs
• Lab Testing
  
  • ELISA
    
    • Antigen assay measures IgG to heparin-PF4 complex
    • Easy, readily available
    • High sensitivity, lower specificity
  • SRA (C-seratonin)
    
    • Detects platelet activation
    • Usually a send-out, labor intensive
    • Very high Se and Sp
    • Used for confirmation
• Clinical Management
  
  • Do not delay treatment waiting for test result
  • STOP all drugs known to cause thrombocytopenia
  • STOP heparin and START non-heparin AC (argatroban IV)
  • Look for hx of heparin exposure, including unrecognized sources (flushes, catheters, prophylaxis doses)
• HIT with Thromboembolism
  
  • 10-25% of HIT cases
  • Venous 4x mor common
    
    • DVT, PE, venous limb gangrene, dural sinus thrombosis
  • Arterial, less common
    
    • Stroke, limb loss, skin necrosis, MI, mesenteric ischemia, adrenal, renal, spinal artery infarction
    • 25-30% mortality
    • 25% amputation