# Plasmapheresis Technique

> Plasmapheresis technique for Dialysis Technology: membrane and centrifugal separation, exchange volumes, replacement fluids, indications and complications.

- Canonical URL: https://prepelephant.com/topics/allied/dialysis-technology/plasmapheresis-technique
- Exam / course: Allied Health · Subject: Dialysis Technology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Plasmapheresis Technique", PrepElephant, https://prepelephant.com/topics/allied/dialysis-technology/plasmapheresis-technique

## 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.