Indications
Plasma exchange may be used to remove
circulating toxins or to replace missing plasma factors. It may be used
in sepsis (e.g. meningococcaemia). In patients with immune mediated disease
(e.g. Guillain–Barre syndrome, thrombotic thrombocytopaenic purpura),
plasma exchange is usually a temporary measure while systemic
immunosuppression takes effect. Most diseases require a daily 3–4L plasma
exchange repeated for at least four
further
occasions over 5–10 days.
Techniques
Cell
separation by centrifugation
Blood
is separated into components in a centrifuge. Plasma (or other specific blood
components) is discarded and a plasma replacement fluid is infused in equal
volume. Centrifugation may be continuous (where blood is withdrawn and returned
by separate needles) or intermittent (where blood is withdrawn and separated,
then returned via the same needle).
Membrane fltration
Plasma is continuously filtered through
a large pore filter (molecular weight cut-off typically 1,000,000D).
Plasma is discarded and replaced by infusion of an equal volume of
replacement fluid. The technique is similar to haemofiltration and uses the same
equipment.
Replacement fluid
Most patients will tolerate replacement
with a plasma substitute. Some fresh frozen plasma will be necessary after the exchange
to replace coagulation factors. The only indication to replace plasma loss with
all fresh frozen plasma is where plasma exchange is being performed to replace missing
plasma factors.
Complications
• Circulatory instability Intravascular
volume changes
Removal of circulating catecholamines
Hypocalcaemia
• Reduced intravascular COP If replacement with
crystalloid
• Infection Reduced plasma
opsonisation
• Bleeding Removal of coagulation factors
Indications
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Autoimmune disease
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Goodpasture’s syndrome
Guillain–Barre syndrome
Myasthenia gravis
Pemphigus
Rapidly progressive glomerulonephritis
Systemic lupus erythematosus
Thrombotic thrombocytopaenic purpura
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|
Immunoproliferative disease
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Cryoglobulinaemia
Multiple myeloma
Waldenstrom’s macroglobulinaemia
|
|
Poisoning
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Paraquat
|
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Others
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Meningococcaemia (possible benefit)
Sepsis (possible benefit)
Reye’s syndrome
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