Ch. 6 - Apheresis

Question 1

What is the difference between TPE and plasmapheresis?

Answer 1

In TPE, donor plasma is the replacement fluid. In plasmapheresis, it may be saline or albumin or other.

Question 2

What kinds of substances can be removed with TPE?

Answer 2

Antibodies, antigen-antibody complexes, cytokines, abnormal plasma proteins, cholesterol, metabolic waste products, drugs

Question 3

What are the two major techniques for cellular separation in apheresis?

Answer 3

Centrifugation (most common)

Filtration technology

Question 4

Why do granulocyte collections often have large numbers of red cells?

Answer 4

Red cells and granulocytes have overlapping densities (can be improved with hetastarch)

Question 5

How can the amount of residual plasma be calculated based on a exchange volume of X?

As a shorthand, how much should be removed for a 1.0-1.5 TPV exchange?

Answer 5

Simple decay formula: y/yo = e^-x

1.0-1.5 TPV = 63-78% removed.

Question 6

How does the size of a pathogenic substance affect its propensity to be removed by pheresis?

Answer 6

Larger, intravascular molecules (eg IgM, fibrinogen, cholesterol) are more easily removed than smaller and interstitial molecules (bilirubin, IgG).

Question 7

What are the four categories of ASFA indication for apheresis?

Answer 7

Category I: Disorders for which apheresis is a first-line therapy.
Category II: Disorders for which it is second-line.
Category III: No established optimum role of apheresis.
Category IV: Established contraindication for apheresis.

Question 8

What are the grades of evidence of ASFA indication for apheresis?

Answer 8

Grade 1A: Strong recommendation, high-quality evidence.
Grade 1B: Strong rec, moderate-quality
Grade 1C: Strong rec, low-quality
Grade 2A: Weak recommendation, high-quality evidence
Grade 2B: Weak rec, moderate-quality
Grade 2C: Weak rec, low-quality

Question 9

What is the most common adverse effect of apheresis?

Answer 9

Symptomatic hypocalcemia due to citrate infusion.

Question 10

What causes hypotension during pheresis?

Answer 10

Infusion of plasma containing bradykinin (worse with use of ace-inhibitors).

Question 11

What are some category I indications for plasma exchange?

Answer 11

• TTP
• Severe hyperviscosity in monoclonal gammopathies
• Anti-GBM disease, ANCA-associated RPGN
• Severe myasthenia gravis, Guillain-barre
• Paraproteinemic polyneuropathies
• Chronic inflammatory demyelinating polyneuropathies
• ABO-incompatible kidney and liver transplant
• NMDA receptor encephalitis
• TMA

Question 12

What are some category I indications for red cell exchange? For leukocytopheresis?

Answer 12

RCE: Acute stroke in sickle cell disease, severe malaria, hereditary hemochromatosis, polycythemia vera

Leukopheresis: Hyperleukocytosis with leukostasis

Question 13

What are some category I indications for photopheresis? For selective lipid removal?

Answer 13

Photopheresis: Erythrodermic cutaneous T-cell lymphomas

Selective lipid removal: Homozygotic familial hypercholesterolemia

Question 14

What effects does pheresis have on drug levels? On coagulation?

Answer 14

Albumin-bound medications and medications with low volume of distribution (as well as high-weight meds) are removed.

Coagulation factors are removed, increasing bleeding risk. This can be offset with plasma.

Question 15

Describe the process of extracorporeal photopheresis.

Answer 15

Mononuclear cells are drawn and concentrated, treated with 8-methoxypsoralen (a photosensitizing agent), then exposed to UVA radiation and reinfused.

Question 16

What agents are used for hematopoietic progenitor cell mobilization?

Answer 16

G-CSF

Plerixafor (anti-CXCR4)

Question 17

What is an adequate dose of CD34+ cells for transplant? How is the collection performed?

Answer 17

> 2 x 10^6 per kg of recipient weight.

HPC collection is long (4-6hrs) and cycles 15-30L of donor plasma (high potential for hypocalcemia).

Question 18

What causes familial hypercholesterolemia?

Answer 18

Heritable mutations in the Apo-B receptors, resulting in gene-dosed elevated cholesterol levels, xanthomata, and atherosclerosis.

Question 19

How is LDL apheresis performed? How often should it be done?

Answer 19

LDL removal may be based on charge (dextran sulfate/polyacrylate), size (membrane filtration), pH precipitation, or immunoadsorption.

Perform once every 1-2 weeks starting in childhood.

Question 20

What are some special requirements for pheresis in the pediatric population?

Answer 20

Need central venous access (peripheral cannot handle catheters / rates of flow).

RBC primes are needed if: Extracorporeal volume >15% of TBV, TBW is <20kg, special cases like severe anemia, hemodynamic instability etc.

Question 21

What kinds of units are selected for sickle cell red cell exchange?

Answer 21

• Partial phenotype matched for C, E, K (Duffy, Kidd, and S if history of antibodies).
• Negative for sickle-cell trait
• Leuko-reduced

Question 22

What, exactly, is rheopheresis? What is it indicated for?

Answer 22

Removal of plasma by centrifugation followed by special filtration for removal of high-molecular-weight substances. It is indicated for retinal conditions (eg AMD).

Question 23

What conditions are treated with therapeutic phlebotomy? How much iron is removed?

Answer 23

Hereditary hemochromatosis, polycythemia vera

Each 500mL unit contains 200-250mg iron

Question 24

What is the role of TPE in treatment of TTP?

Answer 24

TPE is first-line to replace deficient ADAMTS-13.

Question 25

What is the only known indication for cryo-poor plasma?

Answer 25

TPE in TTP (however, some data suggests it is not ideal, resulting in more frequent acute exacerbations of TTP)