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Hematology Unit 1 > Anemia - Hemolysis (complete) > Flashcards

Anemia - Hemolysis (complete) Flashcards

1
Q

Define hemolysis

A
  • Decreased in red cell survival

- Increased in turnover beyond standard norms

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2
Q

What are the two main mechanisms of increased destruction of RBC intravascular and extravascular hemolysis?

A

1) Intravascular — Turnover with the vascular space

2) Extravascular —- Through ingestion and clearance by macrophages of the reticuloendothelial system (RE)

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3
Q

Describe intravascular hemolysis

A
  • RBCs release Hb into circulation
  • Tetramer form of Hb is unstable —» dissociates and bind to haptoglobin —» removed by liver
  • Fe from Hb is oxidized to form methemoglobin —» metheme binds to albumin —» converted to bilirubin
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4
Q

Describe extravascular hemolysis

A
  • Heme separated from globin (via macros digestion) —> Fe removed and stored in ferritin —> porphyrin ring converted to bilirubin
  • Bilirubin + glucuronic acid converted to H2O soluble compound
  • Secreted into biliary tract then small bowel, it dissociates and becomes urobilirubin
  • Ultimately excreted by kidney
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5
Q

What are the relevant clinical lab tests for hemolysis?

A
  • Morphology: spherocytes, fragments
  • Retic count: Increased
  • Bilirubin: Increased
  • Hb: Increased (intravascular)
  • Haptoglobin: Decreased (intravascular)
  • Methemalbumin: Increased (intravascular)
  • LDH/SGOT: Increased
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6
Q

Describe the major constituents of the RBC membrane and cytoskeleton

A
  • Phospho/glycolipids
  • Glycophorin
  • Cholesterol
  • Actin
  • Spectrin
  • Kinase
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7
Q

What are the major defects in hereditary spherocytosis?

A
  • Spectrin: reduced synthesis, unstable, dysfunctional
  • Ankyrin: reduced synthesis, unstable, dysfunctional
  • Band 3: reduced incorporation into membrane, loss of band 3/associated lipids from membrane

Overall: LOSS OF PLASMA MEMBRANE and MICROSPHEROCYTE FORMATION

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8
Q

What are the clinical findings for hereditary spherocytosis?

A
  • Anemia
  • Jaundice
  • Splenomegaly
Auto dom (75%)
Auto rec (25%)
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9
Q

What are the lab findings for hereditary spherocytosis?

A
  • ^ retic count/index
  • ^ MCHC
  • decreased MCV
  • spherocytes on smear
  • variable Hct and Hb
  • **unconjugated hyperbilirubinemia*****
  • abnormal osmotic fragility test
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10
Q

Interpret an osmotic fragility test for diagnosis of hereditary spherocytosis

A

Measures in vitro lysis of RBCs suspended in solutions of decreasing osmolarity

  • normal RBCs: swell in hypotonic solutions, then burst
  • spherocytes: lyse in solutions of higher osmolarity than normal RBCs — more sensitive to decrease in osmolarity

Spherocytes would shift curve to the left

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11
Q

Explain when splenectomy is needed for treatment of hereditary spherocytosis

A
  • if issues are chronic, this will resolve clinical manifestations
  • after splenectomy, spherocytes are present on peripheral blood smear but RBC survival is relatively normal

Do not do this for kids under 5 — immune system not fully developed

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12
Q

Explain how G6PD deficiency affect energy/antioxidant pathways

A

Normal: provides protection against oxidant stress

Early loss:

  • Inability to restore reduced glutathione —> with oxidant stress, denatured Hb attaches to membrane
  • Spectrin damaged

Decreased deformability of RBC —> trapped in spleen —-> extravascular hemolysis

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13
Q

Explain how pyruvate kinase deficiency affect energy/antioxidant pathways

A
  • Decrease in converting phosphoenolpyruvate to pyruvate —> decreased ATP, increased 2,3-DPG
  • Loss of membrane plasticity, increase in rigidity
  • Increase destruction in spleen
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14
Q

Describe the inheritance patterns of G6PD and pyruvate kinase insufficiency

A

G6PD: X linked recessive

Pyruvate:

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15
Q

What are the clinical findings of G6PD deficiency?

A
  • Intermittent episodes of acute anemia
  • hyperbilirubinemia
  • hemolysis
  • reticulocytosis
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16
Q

What are the lab findings of G6PD deficiency?

A
  • Microspherocytes
  • blister cells
  • bite cells
17
Q

What are the clinical findings of pyruvate kinase deficiency?

A
  • Variable chronic anemia
  • Hemolysis
  • Splenomegaly
  • Gallstones
  • Aplastic crises
18
Q

What are the lab findings of pyruvate kinase deficiency?

A
  • mild to severe anemia
  • ^ retic count/index
  • no specific morphology
19
Q

List some major food, drugs, chemicals that induce hemolytic anemia in pts w/ G6PD deficiency

A
  • fava beans
  • methylene blue
  • TNT
  • Tylenol
  • Vit C
  • Isoniazid
  • Vit K
20
Q

Describe the pathophysiology and site of RBC destruction of immune-mediated hemolysis

A
  • Abs to universal RBC Ags
  • two types:
    1) cold
    2) warm
21
Q

Describe cold Abs as it relates to immune-mediated hemolysis

A
  • IgG or IgM
  • Transiently bind RBC in cooler areas of body (fingers, toes, ears, skin)
  • Aggresively activate complement through C(5-9) complex
  • Causes intravascular hemolysis
22
Q

Describe warm Abs as it relates to immune-mediated hemolysis

A
  • IgG
  • High affinity to RBC membrane
  • Very little and incomplete complement activation
  • Causes extravascular hemolysis
23
Q

Describe the direct antiglobulin test (DAT or direct Coombs)

A
  • adds Coombs reagent to blood
  • Evaluates presence of IgG or C3d or C4d on surface of pt’s RBCs
  • If present, agglutination occurs
24
Q

Describe the indirect antiglobulin test (IAT or indirect Coombs)

A

Detects ability of pt’s serum to bind IgG and/or complement to test normal RBCs

25
Q

Distinguish warm Ab-induced hemolytic anemia from cold Ab-induced

A

Warm:

    • DAT (strong IgG,+/- weak complement)
  • Maximal reactivity at 37 Celsius

Cold:

    • DAT (complement only, no IgG)
  • Maximal reactivity at 4 Celsius
26
Q

List the risks and benefits of splenectomy

A

Benefits:
- helps manage hemolytic anemia

Risk:

  • overwhelming sepsis (b/c of pneumonia)
  • highest risk in kids <5yo
27
Q

What type of prophylactic anti-biotics must be used post-splenectomy

A

Penicillin given daily during childhood

28
Q

Describe the role of vaccination in splenectomy

A
  • Protects against sepsis

- vaccinate against HIB, Pneumonia

Hematology Unit 1 (12 decks)

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