Plasmapheresis Technique

Prepared and reviewed by the PrepElephant Academic Review Team

First published 2 Oct 2026 · Spot an error?

On this page

Direct answer
What you must remember
Running a plasma exchange for Guillain-Barré syndrome
Where the exam probes
Frequently asked questions
Related topics

Direct answer

Therapeutic plasma exchange separates and discards the patient's plasma — carrying antibodies, immune complexes and abnormal proteins — replacing it with donor albumin or fresh frozen plasma, using either centrifugal cell separators or membrane plasma filters on dialysis-style machines. A session removes about 1-1.5 plasma volumes (plasma volume is roughly 40 mL/kg, or 0.07 × weight × (1 - haematocrit)), typically daily or on alternate days for 5-7 exchanges. Indications where exchange is first-line include Guillain-Barré syndrome, myasthenic crisis, thrombotic thrombocytopenic purpura and hyperviscosity syndromes; the signature complications are citrate-induced hypocalcaemia, hypotension, and coagulopathy when FFP is withheld.

What you must remember

Two technologies: centrifugal separation (density-based, also harvests cells) and membrane filtration (plasmafilter of roughly 0.2-0.5 micron pore size, run on standard HD platforms) — the membrane route is the dialysis technologist's home ground.
Volume arithmetic: plasma volume ≈ 40 mL/kg (formula 0.07 × kg × (1 - Hct)); exchanging 1 volume removes about 60-65 per cent of an intravascular substance, 1.5 volumes about 75 per cent.
Replacement: 5 per cent albumin as default (with saline balance), fresh frozen plasma when bleeding, thrombotic microangiopathy or factor deficiency demands it, and calcium supplementation running alongside.
First-line indications to list: Guillain-Barré syndrome (equivalent to IV immunoglobulin), myasthenia gravis crisis, TTP (exchange plus steroids; do not transfuse platelets), Goodpasture syndrome (with immunosuppression), hyperviscosity of Waldenstrom macroglobulinaemia.
Settings on a membrane filter: blood flow 100-150 mL/min, transmembrane pressure kept low, filtration rate matching the replacement pump to hold isovolaemia.
Citrate safety: perioral tingling, Chvostek sign, QT prolongation — the same hypocalcaemia ladder as in CRRT and apheresis platelet donation; oral calcium and slow rates blunt it.
Complications: hypotension (volume mismatch), hypocalcaemia, allergic reactions to plasma, hypofibrinogenaemia and hypokalaemia after repeated exchanges, and access-related issues.
Schedule pattern: daily or alternate-day exchanges, 5-7 procedures per course, with clinical endpoints (respiratory force in GBS, platelet recovery in TTP) steering duration.

Running a plasma exchange for Guillain-Barré syndrome

A 34-year-old man, ten days after a diarrhoeal illness, now cannot lift his head off the pillow and his vital capacity is falling. Neurology prescribes five alternate-day exchanges of 1.5 plasma volumes. His plasma volume: 0.07 × 68 × (1 - 0.42) ≈ 2.76 litres, so 1.5 volumes is about 4.1 L per session. The machine is set with the plasmafilter, blood flow 120 mL/min, and the replacement — 5 per cent albumin with the final portion as saline-potassium to blunt hypokalaemia — is pumped in at the exact rate plasma comes off, because a 500 mL mismatch in either direction is a hypotensive or fluid-overload event in a patient who cannot breathe his way out of it.

Halfway through the first session his lips tingle: citrate from the anticoagulant and the albumin's citrate load is chelating ionised calcium. Slow the flow, give calcium gluconate per protocol, and the paraesthesia settles — documented, and pre-empted with oral calcium from session two. By the third exchange his plasma fibrinogen has fallen (albumin contains none), which is expected and simply timed against the next session; a bleeding patient would instead receive FFP as part of replacement. By exchange five he is off the descending limb, and the technologist's log — volumes, pressures, calcium events, vitals — is what made the course safe rather than eventful.

Where the exam probes

Dialysis Technology and allied papers test three seams. First, mechanism versus modality: plasmapheresis removes plasma by separation (size or density), while dialysis removes solutes by gradient — so exchange clears albumin-bound toxins and antibodies that no dialyser touches, the single sentence worth saying in a viva. Second, the TTP trap: plasma exchange is the treatment and platelet transfusion is contraindicated (fuels thrombosis) — a classic MCQ pairing. Third, numbers: 1-1.5 plasma volumes per session, roughly 40 mL/kg plasma volume, 5-7 sessions; and hypocalcaemia as the commonest procedure-related adverse effect, recognised first as perioral tingling.

Frequently asked questions

How is plasma volume estimated for an exchange session?

Approximately 40 mL/kg, calculated as 0.07 × body weight × (1 - haematocrit); a session typically exchanges 1 to 1.5 of these volumes.

Which diseases make plasma exchange a first-line therapy?

Guillain-Barré syndrome, myasthenic crisis, thrombotic thrombocytopenic purpura, Goodpasture syndrome with immunosuppression, and hyperviscosity syndromes such as Waldenstrom macroglobulinaemia.

What replacement fluids are used and when?

Five per cent albumin as the default replacement, with fresh frozen plasma reserved for bleeding risk, thrombotic microangiopathy or factor depletion.

Why does hypocalcaemia occur during plasmapheresis?

Citrate in the anticoagulant and the albumin preparation chelates ionised calcium, producing perioral tingling, tetany and QT prolongation unless calcium is supplemented.

How does plasmapheresis remove toxins that dialysis cannot?

Separation discards the entire plasma fraction, so albumin-bound drugs and antibodies leave with it, unlike dialysis which only moves water-soluble solutes across a gradient.