What is plasmapheresis?

Plasmapheresis: A Therapeutic Procedure for Removing Pathogenic Substances from Blood

Plasmapheresis is a medical procedure that mechanically removes circulating antibodies and other pathogenic substances from the bloodstream by separating plasma from blood cells, replacing it with albumin or fresh frozen plasma, and returning the reconstituted blood to the patient. 1

Definition and Mechanism

Plasmapheresis (also called therapeutic plasma exchange) is an extracorporeal therapy that:

• Separates plasma from cellular blood components using either membrane filtration or centrifugation techniques 2, 1
• Removes pathogenic elements including autoantibodies, immune complexes, and protein-bound toxins 3
• Reconstitutes blood with replacement fluid (typically albumin or fresh frozen plasma) before reinfusing it back into the patient 2

The standard volume processed during a session is approximately 60 ml/kg of the patient's weight, which for a 70 kg patient would be about 4.2 liters of plasma exchanged 1.

Types of Plasmapheresis

There are several variants of plasmapheresis:

• Plasma exchange: The most common form in the United States due to lower cost and ease of use, involves removing plasma and replacing it with albumin or fresh frozen plasma 2
• Double-filtration plasmapheresis: Uses two filters to selectively remove specific plasma components 4
• Immunoadsorption plasmapheresis: Selectively removes only immunoglobulins, avoiding the need for replacement fluids 2, 5

Replacement Fluids

The choice of replacement fluid depends on the clinical indication:

• 5% albumin solution: Primary replacement fluid for most indications including autoimmune disorders 1
• Fresh frozen plasma (FFP): Used for conditions requiring replacement of clotting factors, such as thrombotic thrombocytopenic purpura or diffuse alveolar hemorrhage 1

Treatment Protocol

A typical plasmapheresis regimen includes:

• Frequency: Daily treatments for acute conditions until clinical improvement, then every other day 1
• Duration: Each session lasts 2-4 hours 1
• Number of treatments: Typically 5-14 total procedures depending on clinical response 1
• Volume exchanged: 1-2 plasma volumes per session 1

Clinical Applications

Plasmapheresis is used in over 100 different medical conditions 3, with established efficacy in:

1. Autoimmune disorders:

   • ANCA-associated vasculitis with pulmonary hemorrhage (7 treatments over 14 days) 1
   • Myasthenia gravis
   • Guillain-Barré syndrome

2. Hematologic disorders:

   • Thrombotic thrombocytopenic purpura (TTP)
   • Hyperviscosity syndromes 1

3. Transplantation:

   • Antibody-mediated rejection in cardiac transplantation 2
   • Desensitization therapy in highly sensitized transplant candidates 2

4. Neurological disorders:

   • Antibody-mediated paraneoplastic neurological syndromes 1

5. Dermatological conditions:

   • Refractory pemphigus vulgaris (not recommended as first-line therapy) 2

6. Pulmonary disorders:

   • Severe autoimmune pulmonary alveolar proteinosis (as rescue therapy) 2

Limitations and Considerations

Plasmapheresis has important limitations:

• Not effective as monotherapy: Should be combined with immunosuppressive medications for sustained benefit 2, 1
• Temporary effect: Without concurrent immunosuppression, antibody levels typically rebound 2
• Removes beneficial substances: Clotting factors and other important plasma proteins are removed along with pathogenic elements 2
• Limited evidence: For many conditions, evidence is based on case reports rather than randomized controlled trials 2

Adverse Effects

Common adverse effects include:

• Hypotensive episodes
• Cutaneous vasculitis
• Coagulation abnormalities
• Increased infection risk when combined with immunosuppression 1
• Electrolyte disturbances, particularly hypocalcemia

Clinical Pearls

• Continuous vital sign monitoring is crucial during the procedure 1
• Calcium supplementation may be needed during treatment 1
• Warming replacement fluids can help prevent complications 1
• Early initiation of plasmapheresis combined with appropriate immunosuppression provides the best outcomes 1
• The procedure is generally well-tolerated with serious complications occurring in only about 0.4% of treatment sessions 2

Plasmapheresis remains an important therapeutic option for rapidly reducing circulating antibodies or immune complexes while other immunosuppressive measures take effect, particularly in life-threatening autoimmune conditions.