Therapeutic Plasma Exchange and Apheresis
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Direct answer
Therapeutic plasma exchange removes a patient's plasma and replaces it with albumin or donor plasma, clearing circulating autoantibodies, immune complexes and paraproteins. The American Society for Apheresis grades its indications into categories, and category I includes thrombotic thrombocytopenic purpura, Guillain-Barre syndrome and symptomatic hyperviscosity. Its commonest serious complications are citrate-induced hypocalcaemia, hypotension and allergic reactions to plasma.
What you must remember
- Procedure: blood is separated by centrifugation or a membrane, the plasma is discarded, and cells are returned with replacement fluid.
- Replacement fluid: fresh frozen plasma in thrombotic thrombocytopenic purpura and when clotting factors are needed; albumin for most other indications, such as Guillain-Barre syndrome.
- TTP: plasma exchange with fresh frozen plasma is first-line therapy alongside immunosuppression, because plasma supplies the missing ADAMTS13 enzyme.
- Guillain-Barre syndrome: plasma exchange is effective when started early in the illness, and intravenous immunoglobulin is an equally effective alternative.
- Myasthenia gravis: used for crisis and before thymectomy or surgery, because the benefit is temporary and immunosuppression is still required.
- Hyperviscosity: symptomatic hyperviscosity, most often from IgM paraprotein in Waldenstrom macroglobulinaemia, is relieved by removing the paraprotein.
- Anticoagulant: citrate is used, and its binding of calcium explains the tingling, cramps and arrhythmias that need calcium replacement.
A stepwise approach to a safe exchange session
Plasma exchange carries real risk, so each session is planned around the indication, the access and the replacement fluid. The sequence below is the order in which a team decides and monitors.
- Confirm the indication. Check the disease against the ASFA category, since exchange is justified only where evidence supports it.
- Secure access. A large-bore central venous catheter is placed, commonly in the femoral or internal jugular vein.
- Choose the replacement fluid. Fresh frozen plasma is used for TTP and coagulopathy, and albumin for most others, because the choice changes allergy and bleeding risk.
- Set the volume and frequency. Each exchange typically replaces one to one and a half plasma volumes, given daily or on alternate days according to the disease.
- Monitor during the session. Track ionised calcium, blood pressure, temperature and allergic reactions, and give calcium gluconate for citrate symptoms.
- Taper and reassess. Clinical improvement, platelet count in TTP or disability scores in neuropathy decide when to stop.
Where the exam tries to catch you
Exam questions test whether exchange is matched to evidence and whether its complications are recognised quickly.
- Trap: Plasma exchange is used for every autoimmune neuropathy. Correct: its place is set by evidence and category, and intravenous immunoglobulin is an equally effective alternative in Guillain-Barre syndrome, so cost and availability often decide.
- Trap: Fresh frozen plasma is the replacement fluid in every case. Correct: albumin is preferred for most indications because it avoids plasma-related reactions, and fresh frozen plasma is reserved for TTP and factor replacement.
- Trap: Citrate-induced hypocalcaemia is treated by stopping the exchange. Correct: calcium is replaced, the infusion rate is adjusted, and the session can usually continue.
Frequently asked questions
What is the ASFA category system for therapeutic plasma exchange?
The American Society for Apheresis grades indications for therapeutic plasma exchange into categories by the strength of evidence. Category I includes conditions with established benefit, such as thrombotic thrombocytopenic purpura, Guillain-Barre syndrome and symptomatic hyperviscosity.
Which replacement fluid is used in plasma exchange for thrombotic thrombocytopenic purpura?
Fresh frozen plasma is the standard replacement fluid in thrombotic thrombocytopenic purpura, because it supplies the ADAMTS13 enzyme that the patient lacks. Albumin is used for most other indications, such as Guillain-Barre syndrome.
Is plasma exchange preferred to intravenous immunoglobulin in Guillain-Barre syndrome?
Plasma exchange and intravenous immunoglobulin are both effective in Guillain-Barre syndrome, and neither is clearly superior. The choice depends on availability, cost, haemodynamic stability and the need for central access.
Which complication of plasma exchange needs immediate calcium replacement?
Citrate-induced hypocalcaemia needs immediate calcium replacement during plasma exchange. Citrate is the anticoagulant used, and perioral tingling, muscle cramps or arrhythmia signal a fall in ionised calcium.
Why is plasma exchange used in myasthenic crisis?
Plasma exchange removes circulating acetylcholine receptor antibodies quickly, which makes it useful in myasthenic crisis and before thymectomy or surgery. Its effect is temporary, so long-term immunosuppression is still needed.